174 results on '"Phantoms, Imaging statistics & numerical data"'
Search Results
2. Phantom Evolution.
- Author
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Harrison JD
- Subjects
- Humans, Phantoms, Imaging statistics & numerical data, Radiation Protection statistics & numerical data
- Published
- 2020
- Full Text
- View/download PDF
3. Usefulness of an additional lead shielding device in reducing occupational radiation exposure during interventional endoscopic procedures: An observational study.
- Author
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Yamada R, Saimyo Y, Tanaka K, Hattori A, Umeda Y, Kuroda N, Tsuboi J, Hamada Y, and Takei Y
- Subjects
- Cholangiopancreatography, Endoscopic Retrograde adverse effects, Cholangiopancreatography, Endoscopic Retrograde statistics & numerical data, Fluoroscopy adverse effects, Gonads radiation effects, Humans, Occupational Injuries prevention & control, Phantoms, Imaging statistics & numerical data, Protective Devices standards, Radiation Dosage, Radiation Injuries prevention & control, Radiation Protection methods, Thyroid Gland radiation effects, Occupational Exposure prevention & control, Radiation Exposure prevention & control, Radiation Protection instrumentation, Radiography, Interventional adverse effects
- Abstract
Adoption of interventional endoscopic procedures is increasing with increasing prevalence of diseases. However, medical radiation exposure is concerning; therefore, radiation protection for medical staff is important. However, there is limited information on the usefulness of an additional lead shielding device during interventional endoscopic procedures. Therefore, we aimed to determine whether an additional lead shielding device protects medical staff from radiation.An X-ray unit (CUREVISTA; Hitachi Medical Systems, Tokyo, Japan) with an over-couch X-ray system was used. Fluoroscopy-associated scattered radiation was measured using a water phantom placed at the locations of the endoscopist, assistant, nurse, and clinical engineer. For each location, measurements were performed at the gonad and thyroid gland/eye levels. Comparisons were performed between with and without the additional lead shielding device and with and without a gap in the shielding device. Additionally, a clinical study was performed with 27 endoscopic retrograde cholangiopancreatography procedures.The scattered radiation dose was lower with than without additional lead shielding at all medical staff locations and decreased by 84.7%, 82.8%, 78.2%, and 83.7%, respectively, at the gonad level and by 89.2%, 86.4%, 91.2%, and 87.0%, respectively, at the thyroid gland/eye level. Additionally, the scattered radiation dose was lower without than with a gap in the shielding device at all locations.An additional lead shielding device could protect medical staff from radiation during interventional endoscopic procedures. However, gaps in protective equipment reduce effectiveness and should be eliminated.
- Published
- 2020
- Full Text
- View/download PDF
4. Comparison of different calculation techniques for absorbed dose assessment in patient specific peptide receptor radionuclide therapy.
- Author
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Finocchiaro D, Berenato S, Bertolini V, Castellani G, Lanconelli N, Versari A, Spezi E, Iori M, Fioroni F, and Grassi E
- Subjects
- Algorithms, Humans, Monte Carlo Method, Radiation Dosage, Receptors, Peptide chemistry, Retrospective Studies, Lutetium chemistry, Phantoms, Imaging statistics & numerical data, Radioisotopes chemistry, Radiometry statistics & numerical data, Receptors, Peptide isolation & purification
- Abstract
Aim: The present work concerns the comparison of the performances of three systems for dosimetry in RPT that use different techniques for absorbed dose calculation (organ-level dosimetry, voxel-level dose kernel convolution and Monte Carlo simulations). The aim was to assess the importance of the choice of the most adequate calculation modality, providing recommendations about the choice of the computation tool., Methods: The performances were evaluated both on phantoms and patients in a multi-level approach. Different phantoms filled with a 177Lu-radioactive solution were used: a homogeneous cylindrical phantom, a phantom with organ-shaped inserts and two cylindrical phantoms with inserts different for shape and volume. A total of 70 patients with NETs treated by PRRT with 177Lu-DOTATOC were retrospectively analysed., Results: The comparisons were performed mainly between the mean values of the absorbed dose in the regions of interest. A general better agreement was obtained between Dose kernel convolution and Monte Carlo simulations results rather than between either of these two and organ-level dosimetry, both for phantoms and patients. Phantoms measurements also showed the discrepancies mainly depend on the geometry of the inserts (e.g. shape and volume). For patients, differences were more pronounced than phantoms and higher inter/intra patient variability was observed., Conclusion: This study suggests that voxel-level techniques for dosimetry calculation are potentially more accurate and personalized than organ-level methods. In particular, a voxel-convolution method provides good results in a short time of calculation, while Monte Carlo based computation should be conducted with very fast calculation systems for a possible use in clinics, despite its intrinsic higher accuracy. Attention to the calculation modality is recommended in case of clinical regions of interest with irregular shape and far from spherical geometry, in which Monte Carlo seems to be more accurate than voxel-convolution methods., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2020
- Full Text
- View/download PDF
5. Towards guidelines to harmonize textural features in PET: Haralick textural features vary with image noise, but exposure-invariant domains enable comparable PET radiomics.
- Author
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Prenosil GA, Weitzel T, Fürstner M, Hentschel M, Krause T, Cumming P, Rominger A, and Klaeser B
- Subjects
- Algorithms, Animals, Fluorodeoxyglucose F18, Humans, Phantoms, Imaging statistics & numerical data, Positron Emission Tomography Computed Tomography standards, Positron Emission Tomography Computed Tomography statistics & numerical data, Positron-Emission Tomography methods, Radiopharmaceuticals, Image Processing, Computer-Assisted methods, Image Processing, Computer-Assisted statistics & numerical data, Positron Emission Tomography Computed Tomography methods
- Abstract
Purpose: Image texture is increasingly used to discriminate tissues and lesions in PET/CT. For quantification or in computer-aided diagnosis, textural feature analysis must produce robust and comparable values. Because statistical feature values depend on image count statistics, we investigated in depth the stability of Haralick features values as functions of acquisition duration, and for common image resolutions and reconstructions., Methods: A homogeneous cylindrical phantom containing 9.6 kBq/ml Ge-68 was repeatedly imaged on a Siemens Biograph mCT, with acquisition durations ranging from three seconds to three hours. Images with 1.5, 2, and 4 mm isometrically spaced voxels were reconstructed with filtered back-projection (FBP), ordered subset expectation maximization (OSEM), and the Siemens TrueX algorithm. We analysed Haralick features derived from differently quantized (3 to 8-bit) grey level co-occurrence matrices (GLCMs) as functions of exposure E, which we defined as the product of activity concentration in a volume of interest (VOI) and acquisition duration. The VOI was a 50 mm wide cube at the centre of the phantom. Feature stability was defined for df/dE → 0., Results: The most stable feature values occurred in low resolution FBPs, whereas some feature values from 1.5 mm TrueX reconstructions ranged over two orders of magnitude. Within the same reconstructions, most feature value-exposure curves reached stable plateaus at similar exposures, regardless of GLCM quantization. With 8-bit GLCM, median time to stability was 16 s and 22 s for FBPs, 18 s and 125 s for OSEM, and 23 s, 45 s, and 76 s for PSF reconstructions, with longer durations for higher resolutions. Stable exposures coincided in OSEM and TrueX reconstructions with image noise distributions converging to a Gaussian. In FBP, the occurrence of stable values coincided the disappearance of negatives image values in the VOI., Conclusions: Haralick feature values depend strongly on exposure, but invariance exists within defined domains of exposure. Here, we present an easily replicable procedure to identify said stable exposure domains, where image noise does not substantially add to textural feature values. Only by imaging at predetermined feature-invariant exposure levels and by adjusting exposure to expected activity concentrations, can textural features have a quantitative use in PET/CT. The necessary exposure levels are attainable by modern PET/CT systems in clinical routine., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2020
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6. Monte Carlo simulations and analysis of transmitted gamma ray spectra through various tissue phantoms.
- Author
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Moradi F, Khandaker MU, Alrefae T, Ramazanian H, and Bradley DA
- Subjects
- Computer Simulation, Female, Humans, Male, Monte Carlo Method, Photons, Radioisotopes adverse effects, Radioisotopes therapeutic use, Scattering, Radiation, Tissue Distribution, Gamma Rays adverse effects, Gamma Rays therapeutic use, Phantoms, Imaging statistics & numerical data, Spectrometry, Gamma statistics & numerical data
- Abstract
Studies of radiation interactions with tissue equivalent material find importance in efforts that seek to avoid unjustifiable dose to patients, also in ensuring quality control of for instance nuclear medicine imaging equipment. Use of the Monte Carlo (MC) simulation tool in such characterization processes allows for the avoidance of costly experiments involving transmitted X- and γ-ray spectrometry. Present work investigates MC simulations of γ-ray transmission through tissue equivalent solid phantoms. Use has been made of a range of radionuclide gamma ray sources,
99m Tc,131 I,137 Cs,60 Co (offering photons in the energy range from a few keV up to low MeV), popularly applied in medicine and in some cases for gauging in industry, obtaining the transmission spectra following their interaction with various phantom materials and thicknesses. In validation of the model, the simulated values of mass attenuation coefficients (μ/ρ) for different phantom materials and thicknesses were found to be in good agreement with reference values (NIST, 2004) to within 1.1% for all material compositions. For all of the primary photon energies and medium thicknesses of interest herein, results show that multiple scattering peaks are generally located at energies lower than 100 keV, although for the larger phantom thicknesses it is more difficult to distinguish single, double and multiple scattering in the gamma spectra. Transmitted photon spectra investigated for water, soft tissue, breast, brain and lung tissue slab phantoms are demonstrated to be practically independent of the phantom material, while a significant difference is observed for the spectra transmitted through bone that was proved to be due to the density effect and not material composition., (Copyright © 2019 Elsevier Ltd. All rights reserved.)- Published
- 2019
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7. Technical Report: A Cost-Effective, Easily Available Tofu Model for Training Residents in Ultrasound-Guided Fine Needle Thyroid Nodule Targeting Punctures.
- Author
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Zhang YF, Li H, and Wang XM
- Subjects
- Female, Humans, Male, Punctures, Radiology, Soy Foods, Ultrasonography methods, Biopsy, Fine-Needle methods, Education, Medical, Graduate methods, Phantoms, Imaging statistics & numerical data, Thyroid Nodule surgery
- Abstract
Objective: To establish a cost-effective and easily available phantom for training residents in ultrasound-guided fine needle thyroid nodule targeting punctures., Materials and Methods: Tofu, drinking straws filled with coupling gel, a urine tube, and 21-gauge needles were used to generate a phantom thyroid with nodules for training. Twelve radiology residents were involved in the study. The puncture success rates were recorded and compared before and after phantom training using the Wilcoxon signed-rank test., Results: On ultrasonography, tofu mimicked the texture of the thyroid. Drinking straws filled with coupling gel mimicked vessels. The urine tube filled with air mimicked the trachea, and 21-gauge needles mimicked small nodules in the transverse section. The entire phantom was similar to the structure of the thyroid and surrounding tissues. The puncture success rates of radiology residents were significantly increased from 34.4 ± 14.2% to 66.7 ± 19.5% after training ( p = 0.003). The phantom was constructed in approximately 10 minutes and materials cost less than CNY 10 (approximately $ 1.5) at a local store., Conclusion: The tofu model was cost-effective, easily attainable, and effective for training residents in ultrasound-guided fine needle thyroid nodule targeting punctures in vitro ., Competing Interests: Conflicts of Interest: The authors have no financial conflicts of interest.
- Published
- 2019
- Full Text
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8. Wiener filter improves diagnostic accuracy of CAD SPECT images-comparison to angiography and CT angiography.
- Author
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Masoomi MA, Al-Shammeri I, Kalafallah K, Elrahman HMA, Ragab O, Ahmed E, Al-Shammeri J, and Arafat S
- Subjects
- Adult, Aged, Female, Humans, Male, Middle Aged, Phantoms, Imaging statistics & numerical data, Single Photon Emission Computed Tomography Computed Tomography methods, Single Photon Emission Computed Tomography Computed Tomography statistics & numerical data, Tomography, Emission-Computed, Single-Photon methods, Angiography methods, Computed Tomography Angiography, Coronary Artery Disease diagnostic imaging, Radiographic Image Enhancement instrumentation, Tomography, Emission-Computed, Single-Photon instrumentation
- Abstract
Many discrepancy in selection of proper filter and its parameters for individual cases exists. The authors investigate the impact of the most common filters on patient NM images with coronary artery disease (CAD), and compare the results with the computerized tomography (CT)-Angio and angiography for accuracy.The investigation initiated by performing various single photon emission computerized tomography (SPECT)/CT scan of the national electrical manufacturers association chest phantoms having hot and cold inserts. Data acquired on GE 670 PRO SPECT/CT; 360Ø, 64 frames, 60 seconds, low energy high resolution (LEHR) 128, low energy general purpose (LEGP) with CT attenuation (120 kV and 170 mA). The images reconstructed with filtered back projection and ITERATIVE ordered-subset expectation maximization utilizing filters; Hann, Butterworth, Metz, Hamming, and Wiener. The Image contrast was calculated to assess absolute nearness of the inserts. Based on the preliminary results, then scans of 92 patients with CAD; 64 males and 28 females, age 41 to 77 years old, who had been reported earlier reprocessed with the nominated filter and were reported by 2 NM expert. The results compared to the earlier reports and to the CT-Angio and angiography.The optimization suggested 3 filters; Wiener (Wi), Metz and Butterworth (But) provide the highest contrast (99- 66.4%) and (81- 32%) for the cold and hot inserts respectively, with the (Wi) filter to be the better option. The reprocessed patients scan with the (Wi) presented an elevated diagnostic accuracy, correlated well with the CT-Angio and angiography results (P < .001 and r = 0.79 for [Wi] and P = .004 and r = 0.39 for [But]). The percentage of the false negative for moderate to severe CAD cases reported using Wi filter reduced from 27% to 7% and similarly for mild CAD cases from 7% to 1%.It appears the Wiener filter could produce results with the highest contrast for phantom imaging of various cold and hot spheres and for the patient data which is more consistent with angiography results, with much-elevated accuracy in intermediate cases (r = 0.79 for Wiener and r = 0.39 for Butterworth vs angiography). However, the optimum parameters obtained for the filters have no relation with the resolution of the imaging system, but the details of the objects could be improved.
- Published
- 2019
- Full Text
- View/download PDF
9. Fusing Infrared and Visible Images of Different Resolutions via Total Variation Model.
- Author
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Du Q, Xu H, Ma Y, Huang J, and Fan F
- Subjects
- Humans, Image Processing, Computer-Assisted methods, Infrared Rays, Phantoms, Imaging statistics & numerical data, Records, Tomography, X-Ray Computed methods, Algorithms, Image Processing, Computer-Assisted statistics & numerical data, Tomography, X-Ray Computed statistics & numerical data
- Abstract
In infrared and visible image fusion, existing methods typically have a prerequisite that the source images share the same resolution. However, due to limitations of hardware devices and application environments, infrared images constantly suffer from markedly lower resolution compared with the corresponding visible images. In this case, current fusion methods inevitably cause texture information loss in visible images or blur thermal radiation information in infrared images. Moreover, the principle of existing fusion rules typically focuses on preserving texture details in source images, which may be inappropriate for fusing infrared thermal radiation information because it is characterized by pixel intensities, possibly neglecting the prominence of targets in fused images. Faced with such difficulties and challenges, we propose a novel method to fuse infrared and visible images of different resolutions and generate high-resolution resulting images to obtain clear and accurate fused images. Specifically, the fusion problem is formulated as a total variation (TV) minimization problem. The data fidelity term constrains the pixel intensity similarity of the downsampled fused image with respect to the infrared image, and the regularization term compels the gradient similarity of the fused image with respect to the visible image. The fast iterative shrinkage-thresholding algorithm (FISTA) framework is applied to improve the convergence rate. Our resulting fused images are similar to super-resolved infrared images, which are sharpened by the texture information from visible images. Advantages and innovations of our method are demonstrated by the qualitative and quantitative comparisons with six state-of-the-art methods on publicly available datasets.
- Published
- 2018
- Full Text
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10. Measuring PET Spatial Resolution Using a Cylinder Phantom Positioned at an Oblique Angle.
- Author
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Lodge MA, Leal JP, Rahmim A, Sunderland JJ, and Frey EC
- Subjects
- Algorithms, Fluorodeoxyglucose F18, Humans, Image Interpretation, Computer-Assisted statistics & numerical data, Positron Emission Tomography Computed Tomography instrumentation, Positron Emission Tomography Computed Tomography standards, Positron Emission Tomography Computed Tomography statistics & numerical data, Positron-Emission Tomography standards, Positron-Emission Tomography statistics & numerical data, Radiopharmaceuticals, Phantoms, Imaging statistics & numerical data, Positron-Emission Tomography instrumentation
- Abstract
A cylinder phantom positioned at a slightly oblique angle with respect to the z -axis of a PET scanner allows for fine sampling of the edge-spread function. We show how this technique can be used to measure the spatial resolution that can be expected with clinical PET protocols, potentially providing more relevant estimates than are typically obtained with established experimental procedures. Methods: A 20-cm-diameter water-filled cylinder phantom containing a uniform
18 F solution was centrally positioned at a small angle with respect to the z -axis of a clinical PET/CT system. The oblique angle ensures that the phantom edge intersects the image matrix differently in different slices. Combining line profiles from multiple slices results in a composite profile with fine sampling. Spatial resolution was measured as the full width at half maximum (FWHM) by fitting a model to the finely sampled edge-spread functions in both radial and axial directions. The technique was validated by controlled modulation of image reconstruction parameters and by comparison with extended phantoms with fillable inserts. Separate experiments with uniform cylinders containing18 F,11 C,13 N,68 Ga, and124 I were used to further assess the proposed method. Results: Controlled adjustment of a gaussian postreconstruction filter was accurately reflected in the measured FWHM values. Recovery coefficients derived using the cylinder FWHM values agreed closely with recovery coefficients derived from physical phantoms over a range of insert-to-background ratios, phantom geometries, and reconstruction protocols. The effect of increasing positron energy was clearly reflected in the FWHM values measured with different isotopes. Conclusion: A method has been developed for measuring the spatial resolution that is achieved with clinical PET protocols, providing more relevant estimates than are typically obtained with established procedures. The proposed method requires no special equipment and is versatile, being capable of measuring resolution for different isotopes as well as for different reconstruction protocols. The new technique promises to aid standardization of PET data acquisition by allowing a more informed selection of reconstruction parameters., (© 2018 by the Society of Nuclear Medicine and Molecular Imaging.)- Published
- 2018
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11. Fuzzy Object Skeletonization: Theory, Algorithms, and Applications.
- Author
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Saha PK, Jin D, Liu Y, Christensen GE, and Chen C
- Subjects
- Animals, Bone and Bones diagnostic imaging, Bone and Bones physiology, Computer Simulation, Humans, Models, Anatomic, Models, Statistical, Phantoms, Imaging statistics & numerical data, Tomography, X-Ray Computed statistics & numerical data, X-Ray Microtomography statistics & numerical data, Algorithms, Computer Graphics statistics & numerical data, Fuzzy Logic
- Abstract
Skeletonization offers a compact representation of an object while preserving important topological and geometrical features. Literature on skeletonization of binary objects is quite mature. However, challenges involved with skeletonization of fuzzy objects are mostly unanswered. This paper presents a new theory and algorithm of skeletonization for fuzzy objects, evaluates its performance, and demonstrates its applications. A formulation of fuzzy grassfire propagation is introduced; its relationships with fuzzy distance functions, level sets, and geodesics are discussed; and several new theoretical results are presented in the continuous space. A notion of collision-impact of fire-fronts at skeletal points is introduced, and its role in filtering noisy skeletal points is demonstrated. A fuzzy object skeletonization algorithm is developed using new notions of surface- and curve-skeletal voxels, digital collision-impact, filtering of noisy skeletal voxels, and continuity of skeletal surfaces. A skeletal noise pruning algorithm is presented using branch-level significance. Accuracy and robustness of the new algorithm are examined on computer-generated phantoms and micro- and conventional CT imaging of trabecular bone specimens. An application of fuzzy object skeletonization to compute structure-width at a low image resolution is demonstrated, and its ability to predict bone strength is examined. Finally, the performance of the new fuzzy object skeletonization algorithm is compared with two binary object skeletonization methods.
- Published
- 2018
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12. Treatment Planning System Calculation Errors Are Present in Most Imaging and Radiation Oncology Core-Houston Phantom Failures.
- Author
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Kerns JR, Stingo F, Followill DS, Howell RM, Melancon A, and Kry SF
- Subjects
- Algorithms, Calibration, Head, Medical Errors statistics & numerical data, Particle Accelerators standards, Phantoms, Imaging statistics & numerical data, Radiotherapy Planning, Computer-Assisted methods, Radiotherapy Planning, Computer-Assisted statistics & numerical data, Radiotherapy, Intensity-Modulated statistics & numerical data, Reference Standards, Phantoms, Imaging standards, Radiotherapy Dosage standards, Radiotherapy Planning, Computer-Assisted standards, Radiotherapy, Intensity-Modulated standards
- Abstract
Purpose: The anthropomorphic phantom program at the Houston branch of the Imaging and Radiation Oncology Core (IROC-Houston) is an end-to-end test that can be used to determine whether an institution can accurately model, calculate, and deliver an intensity modulated radiation therapy dose distribution. Currently, institutions that do not meet IROC-Houston's criteria have no specific information with which to identify and correct problems. In the present study, an independent recalculation system was developed to identify treatment planning system (TPS) calculation errors., Methods and Materials: A recalculation system was commissioned and customized using IROC-Houston measurement reference dosimetry data for common linear accelerator classes. Using this system, 259 head and neck phantom irradiations were recalculated. Both the recalculation and the institution's TPS calculation were compared with the delivered dose that was measured. In cases in which the recalculation was statistically more accurate by 2% on average or 3% at a single measurement location than was the institution's TPS, the irradiation was flagged as having a "considerable" institutional calculation error. The error rates were also examined according to the linear accelerator vendor and delivery technique., Results: Surprisingly, on average, the reference recalculation system had better accuracy than the institution's TPS. Considerable TPS errors were found in 17% (n=45) of the head and neck irradiations. Also, 68% (n=13) of the irradiations that failed to meet the IROC-Houston criteria were found to have calculation errors., Conclusions: Nearly 1 in 5 institutions were found to have TPS errors in their intensity modulated radiation therapy calculations, highlighting the need for careful beam modeling and calculation in the TPS. An independent recalculation system can help identify the presence of TPS errors and pass on the knowledge to the institution., (Copyright © 2017 Elsevier Inc. All rights reserved.)
- Published
- 2017
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13. The importance of BMI in dosimetry of 153 Sm-EDTMP bone pain palliation therapy: A Monte Carlo study.
- Author
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Fallahpoor M, Abbasi M, Asghar Parach A, and Kalantari F
- Subjects
- Body Mass Index, Bone Neoplasms physiopathology, Bone Neoplasms secondary, Female, Humans, Monte Carlo Method, Palliative Care, Phantoms, Imaging statistics & numerical data, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted statistics & numerical data, Bone Neoplasms radiotherapy, Organometallic Compounds therapeutic use, Organophosphorus Compounds therapeutic use, Pain radiotherapy, Radioisotopes therapeutic use, Radiopharmaceuticals therapeutic use, Radiotherapy Planning, Computer-Assisted methods, Samarium therapeutic use
- Abstract
Using digital phantoms as an atlas compared to acquiring CT data for internal radionuclide dosimetry decreases patient overall radiation dose and reduces the required analysis effort and time for organ segmentation. The drawback is that the phantom may not match exactly with the patient. We assessed the effect of varying BMIs on dosimetry results for a bone pain palliation agent,
153 Sm-EDTMP. The simulation was done using the GATE Monte Carlo code. Female XCAT phantoms with the following different BMIs were employed: 18.6, 20.8, 22.1, 26.8, 30.3 and 34.7kg/m2 . S-factors (mGy/MBq.s) and SAFs (kg-1 ) were calculated for the dosimetry of the radiation from major source organs including spine, ribs, kidney and bladder into different target organs as well as whole body dosimetry from spine. The differences in dose estimates from different phantoms compared to those from the phantom with BMI of 26.8kg/m2 as the reference, were calculated for both gamma and beta radiations. The relative differences (RD) of the S-factors or SAFs from the values of reference phantom were calculated. RDs greater than 10% and 100% were frequent in radiations to organs for photon and beta particles, respectively. The relative differences in whole body SAFs from the reference phantom were 15.4%, 7%, 4.2%, -9.8% and -1.4% for BMIs of 18.6, 20.8, 22.1, 30.3 and 34.7kg/m2 , respectively. The differences in whole body S-factors for the phantoms with BMIs of 18.6, 20.8, 22.1, 30.3 and 34.7kg/m2 were 39.5%, 19.4%, 8.8%, -7.9% and -4.3%, respectively. The dosimetry of the gamma photons and beta particles changes substantially with the use of phantoms with different BMIs. The change in S-factors is important for dose calculation and can change the prescribed therapeutic dose of153 Sm-EDTMP. Thus a phantom with BMI better matched to the patient is suggested for therapeutic purposes where dose estimates closer to those in the actual patient are required., (Copyright © 2017. Published by Elsevier Ltd.)- Published
- 2017
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14. Validation of a CT-guided intervention robot for biopsy and radiofrequency ablation: experimental study with an abdominal phantom.
- Author
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Won HJ, Kim N, Kim GB, Seo JB, and Kim H
- Subjects
- Abdomen, Biopsy, Needle methods, Catheter Ablation methods, Fluoroscopy methods, Humans, Image-Guided Biopsy methods, Liver, Needles, Reproducibility of Results, Software, Tomography, X-Ray Computed methods, Biopsy, Needle instrumentation, Catheter Ablation instrumentation, Fluoroscopy instrumentation, Image-Guided Biopsy instrumentation, Phantoms, Imaging statistics & numerical data, Robotics methods
- Abstract
Purpose: We aimed to evaluate the accuracy of a needle-placement robot for biopsy and radiofrequency ablation on an abdominal phantom., Methods: A master-slave robotic system has been developed that includes a needle-path planning system and a needle-inserting robot arm with computed tomography (CT) and CT fluoroscopy guidance. For evaluation of its accuracy in needle placement, a commercially available abdominal phantom (Model 057A; CIRS Inc.) was used. The liver part of the phantom contains multiple spherical simulated tumors of three different size spheres. Various needle insertion trials were performed in the transverse plane and caudocranial plane two nodule sizes (10 mm and 20 mm in diameter) to test the reliability of this robot. To assess accuracy, a CT scan was performed after each trial with the needle in situ., Results: The overall error was 2 mm (0-2.6 mm), which was calculated as the distance from the planned trajectory before insertion to the actual needle trajectory after insertion. The standard deviations of the insertions on two nodules (10 mm and 20 mm in diameter) were 0.5 mm and 0.2 mm, respectively., Conclusion: The CT-compatible needle placement robot for biopsy and radiofrequency ablation shows relatively acceptable accuracy and could be used for radiofrequency ablation of nodules ≥10 mm under CT fluoroscopy guidance.
- Published
- 2017
- Full Text
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15. Fast and Quantitative T1ρ-weighted Dynamic Glucose Enhanced MRI.
- Author
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Schuenke P, Paech D, Koehler C, Windschuh J, Bachert P, Ladd ME, Schlemmer HP, Radbruch A, and Zaiss M
- Subjects
- Aged, Brain metabolism, Brain pathology, Brain Neoplasms metabolism, Brain Neoplasms pathology, Contrast Media pharmacokinetics, Glioblastoma metabolism, Glioblastoma pathology, Glucose pharmacokinetics, Humans, Injections, Intravenous, Male, Phantoms, Imaging statistics & numerical data, Reproducibility of Results, Brain diagnostic imaging, Brain Neoplasms diagnostic imaging, Contrast Media metabolism, Glioblastoma diagnostic imaging, Glucose metabolism, Image Enhancement methods, Magnetic Resonance Imaging methods
- Abstract
Common medical imaging techniques usually employ contrast agents that are chemically labeled, e.g. with radioisotopes in the case of PET, iodine in the case of CT or paramagnetic metals in the case of MRI to visualize the heterogeneity of the tumor microenvironment. Recently, it was shown that natural unlabeled D-glucose can be used as a nontoxic biodegradable contrast agent in Chemical Exchange sensitive Spin-Lock (CESL) magnetic resonance imaging (MRI) to detect the glucose uptake and potentially the metabolism of tumors. As an important step to fulfill the clinical needs for practicability, reproducibility and imaging speed we present here a robust and quantitative T
1ρ -weighted technique for dynamic glucose enhanced MRI (DGE-MRI) with a temporal resolution of less than 7 seconds. Applied to a brain tumor patient, the new technique provided a distinct DGE contrast between tumor and healthy brain tissue and showed the detailed dynamics of the glucose enhancement after intravenous injection. Development of this fast and quantitative DGE-MRI technique allows for a more detailed analysis of DGE correlations in the future and potentially enables non-invasive diagnosis, staging and monitoring of tumor response to therapy., Competing Interests: The authors declare no competing financial interests.- Published
- 2017
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16. Activity concentration measurements using a conjugate gradient (Siemens xSPECT) reconstruction algorithm in SPECT/CT.
- Author
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Armstrong IS and Hoffmann SA
- Subjects
- Bias, Gamma Cameras statistics & numerical data, Humans, Reproducibility of Results, Single Photon Emission Computed Tomography Computed Tomography instrumentation, Single Photon Emission Computed Tomography Computed Tomography statistics & numerical data, Tomography, Emission-Computed, Single-Photon instrumentation, Algorithms, Phantoms, Imaging statistics & numerical data, Tomography, Emission-Computed, Single-Photon statistics & numerical data
- Abstract
The interest in quantitative single photon emission computer tomography (SPECT) shows potential in a number of clinical applications and now several vendors are providing software and hardware solutions to allow 'SUV-SPECT' to mirror metrics used in PET imaging. This brief technical report assesses the accuracy of activity concentration measurements using a new algorithm 'xSPECT' from Siemens Healthcare. SPECT/CT data were acquired from a uniform cylinder with 5, 10, 15 and 20 s/projection and NEMA image quality phantom with 25 s/projection. The NEMA phantom had hot spheres filled with an 8 : 1 activity concentration relative to the background compartment. Reconstructions were performed using parameters defined by manufacturer presets available with the algorithm. The accuracy of activity concentration measurements was assessed. A dose calibrator-camera cross-calibration factor (CCF) was derived from the uniform phantom data. In uniform phantom images, a positive bias was observed, ranging from ∼6% in the lower count images to ∼4% in the higher-count images. On the basis of the higher-count data, a CCF of 0.96 was derived. As expected, considerable negative bias was measured in the NEMA spheres using region mean values whereas positive bias was measured in the four largest NEMA spheres. Nonmonotonically increasing recovery curves for the hot spheres suggested the presence of Gibbs edge enhancement from resolution modelling. Sufficiently accurate activity concentration measurements can easily be measured on images reconstructed with the xSPECT algorithm without a CCF. However, the use of a CCF is likely to improve accuracy further. A manual conversion of voxel values into SUV should be possible, provided that the patient weight, injected activity and time between injection and imaging are all known accurately.
- Published
- 2016
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17. Characterization of a 0.35T MR system for phantom image quality stability and in vivo assessment of motion quantification.
- Author
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Saenz DL, Yan Y, Christensen N, Henzler MA, Forrest LJ, Bayouth JE, and Paliwal BR
- Subjects
- Animals, Dogs, Four-Dimensional Computed Tomography, Humans, Imaging, Three-Dimensional, Magnetic Resonance Imaging methods, Models, Animal, Motion, Radiotherapy, Intensity-Modulated methods, Tomography, X-Ray Computed, Phantoms, Imaging standards, Phantoms, Imaging statistics & numerical data, Radiotherapy Planning, Computer-Assisted methods, Radiotherapy, Image-Guided methods
- Abstract
ViewRay is a novel MR-guided radiotherapy system capable of imaging in near real-time at four frames per second during treatment using 0.35T field strength. It allows for improved gating techniques and adaptive radiotherapy. Three cobalt-60 sources (~ 15,000 Curies) permit multiple-beam, intensity-modulated radiation therapy. The primary aim of this study is to assess the imaging stability, accuracy, and automatic segmentation algorithm capability to track motion in simulated and in vivo targets. Magnetic resonance imaging (MRI) characteristics of the system were assessed using the American College of Radiology (ACR)-recommended phantom and accreditation protocol. Images of the ACR phantom were acquired using a head coil following the ACR scanning instructions. ACR recommended T1- and T2-weighted sequences were evaluated. Nine measurements were performed over a period of seven months, on just over a monthly basis, to establish consistency. A silicon dielectric gel target was attached to the motor via a rod. 40 mm total amplitude was used with cycles of 3 to 9 s in length in a sinusoidal trajectory. Trajectories of six moving clinical targets in four canine patients were quantified and tracked. ACR phantom images were analyzed, and the results were compared with the ACR acceptance levels. Measured slice thickness accuracies were within the acceptance limits. In the 0.35 T system, the image intensity uniformity was also within the ACR acceptance limit. Over the range of cycle lengths, representing a wide range of breathing rates in patients imaged at four frames/s, excellent agreement was observed between the expected and measured target trajectories. In vivo canine targets, including the gross target volume (GTV), as well as other abdominal soft tissue structures, were visualized with inherent MR contrast, allowing for preliminary results of target tracking.
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- 2015
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18. Two Realistic Beagle Models for Dose Assessment.
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Stabin MG, Kost SD, Segars WP, and Guilmette RA
- Subjects
- Animals, Female, Male, Mice, Models, Animal, Organ Size, Phantoms, Imaging statistics & numerical data, Radiation Dosage, Radiometry statistics & numerical data, Rats, Dogs anatomy & histology, Radiometry methods
- Abstract
Previously, the authors developed a series of eight realistic digital mouse and rat whole body phantoms based on NURBS technology to facilitate internal and external dose calculations in various species of rodents. In this paper, two body phantoms of adult beagles are described based on voxel images converted to NURBS models. Specific absorbed fractions for activity in 24 organs are presented in these models. CT images were acquired of an adult male and female beagle. The images were segmented, and the organs and structures were modeled using NURBS surfaces and polygon meshes. Each model was voxelized at a resolution of 0.75 × 0.75 × 2 mm. The voxel versions were implemented in GEANT4 radiation transport codes to calculate specific absorbed fractions (SAFs) using internal photon and electron sources. Photon and electron SAFs were then calculated for relevant organs in both models. The SAFs for photons and electrons were compatible with results observed by others. Absorbed fractions for electrons for organ self-irradiation were significantly less than 1.0 at energies above 0.5 MeV, as expected for many of these small-sized organs, and measurable cross irradiation was observed for many organ pairs for high-energy electrons (as would be emitted by nuclides like 32P, 90Y, or 188Re). The SAFs were used with standardized decay data to develop dose factors (DFs) for radiation dose calculations using the RADAR Method. These two new realistic models of male and female beagle dogs will be useful in radiation dosimetry calculations for external or internal simulated sources.
- Published
- 2015
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19. Adjustment of chest wall thickness of voxel phantom for numerical efficiency calibration of lung counters.
- Author
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Liye L, Hua L, Wei C, Yunshi X, Qinjian C, Yuan Z, and Junli L
- Subjects
- Calibration, Computer Simulation, Humans, Imaging, Three-Dimensional, Lung diagnostic imaging, Models, Anatomic, Monte Carlo Method, Photons, Radiation Monitoring statistics & numerical data, Radionuclide Imaging, Thoracic Wall diagnostic imaging, Lung radiation effects, Phantoms, Imaging statistics & numerical data, Thoracic Wall anatomy & histology, Thoracic Wall radiation effects
- Abstract
A modification method was implemented to adjust the chest wall thickness of human voxel phantom for the purpose of numerical efficiency calibration of lung counters. This method was based on two basic mathematical morphology operations (dilation and erosion) and combined with proper structure elements. The voxel model of LLNL torso phantom was used as a reference to validate the modification process. The chest wall was mathematically modified from the starting phantom with no overlay plate to the target with an overlay plate of 24-mm thickness. The influences of different structure elements on detection efficiency were discussed. When diamond or square structure elements were used, the calculated efficiency was overestimated or underestimated by ∼40 % for 17.5-keV photons, compared with that of target phantom. In contrast, it was shown a good agreement with a deviation of <3 % when the hybrid structure elements were adopted. A similar adjustment method can be used for 3D modification of human voxel phantom to keep the body's anatomical geometry without distortion during the adjustment process., (© The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)
- Published
- 2014
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20. The influence of anatomical noise on optimal beam quality in mammography.
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Cederström B and Fredenberg E
- Subjects
- Biophysical Phenomena, Breast Diseases diagnostic imaging, Breast Neoplasms diagnostic imaging, Calcinosis diagnostic imaging, Female, Humans, Mammography standards, Models, Anatomic, Models, Theoretical, Phantoms, Imaging statistics & numerical data, Photons, Radiation Dosage, Signal-To-Noise Ratio, Mammography statistics & numerical data, Radiographic Image Enhancement standards
- Abstract
Purpose: Beam-quality optimization in digital mammography traditionally considers detection of a target obscured by quantum noise in a homogeneous background. This does not correspond well to the clinical imaging task because real mammographic images contain a complex superposition of anatomical structures, resulting in anatomical noise that may dominate over quantum noise. The purpose of this paper is to assess the influence on optimal beam quality in mammography when anatomical noise is taken into account., Methods: The detectability of microcalcifications and masses was quantified using a theoretical ideal-observer model that included quantum noise as well as anatomical noise and a simplified model of a photon-counting mammography system. The outcome was experimentally verified using two types of simulated tissue phantoms., Results: The theoretical model showed that the detectability of tumors and microcalcifications behaves differently with respect to beam quality and dose. The results for small microcalcifications were similar to what traditional optimization methods yield, which is to be expected because quantum noise dominates over anatomical noise at high spatial frequencies. For larger tumors, however, low-frequency anatomical noise was the limiting factor. Because anatomical structure noise has similar energy dependence as tumor contrast, the optimal x-ray energy was found to be higher and the useful energy region was wider than traditional methods suggest. A simplified scalar model was able to capture this behavior using a fitted noise mixing parameter. The phantom measurements confirmed these theoretical results., Conclusions: It was shown that since quantum noise constitutes only a small fraction of the noise, the dose could be reduced substantially without sacrificing tumor detectability. Furthermore, when anatomical noise is included, the tube voltage can be increased well beyond what is conventionally considered optimal and used clinically, without loss of image quality. However, no such conclusions can be drawn for the more complex mammographic imaging task as a whole.
- Published
- 2014
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21. A three-dimensional head-and-neck phantom for validation of multimodality deformable image registration for adaptive radiotherapy.
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Singhrao K, Kirby N, and Pouliot J
- Subjects
- Algorithms, Biophysical Phenomena, Head and Neck Neoplasms pathology, Humans, Imaging, Three-Dimensional statistics & numerical data, Models, Anatomic, Plastics, Radiographic Image Interpretation, Computer-Assisted, Radiotherapy Planning, Computer-Assisted statistics & numerical data, Radiotherapy, High-Energy statistics & numerical data, Radiotherapy, Image-Guided statistics & numerical data, Tomography, X-Ray Computed statistics & numerical data, Head and Neck Neoplasms diagnostic imaging, Head and Neck Neoplasms radiotherapy, Phantoms, Imaging statistics & numerical data
- Abstract
Purpose: To develop a three-dimensional (3D) deformable head-and-neck (H&N) phantom with realistic tissue contrast for both kilovoltage (kV) and megavoltage (MV) imaging modalities and use it to objectively evaluate deformable image registration (DIR) algorithms., Methods: The phantom represents H&N patient anatomy. It is constructed from thermoplastic, which becomes pliable in boiling water, and hardened epoxy resin. Using a system of additives, the Hounsfield unit (HU) values of these materials were tuned to mimic anatomy for both kV and MV imaging. The phantom opens along a sagittal midsection to reveal radiotransparent markers, which were used to characterize the phantom deformation. The deformed and undeformed phantoms were scanned with kV and MV imaging modalities. Additionally, a calibration curve was created to change the HUs of the MV scans to be similar to kV HUs, (MC). The extracted ground-truth deformation was then compared to the results of two commercially available DIR algorithms, from Velocity Medical Solutions and mim software., Results: The phantom produced a 3D deformation, representing neck flexion, with a magnitude of up to 8 mm and was able to represent tissue HUs for both kV and MV imaging modalities. The two tested deformation algorithms yielded vastly different results. For kV-kV registration, mim produced mean and maximum errors of 1.8 and 11.5 mm, respectively. These same numbers for Velocity were 2.4 and 7.1 mm, respectively. For MV-MV, kV-MV, and kV-MC Velocity produced similar mean and maximum error values. mim, however, produced gross errors for all three of these scenarios, with maximum errors ranging from 33.4 to 41.6 mm., Conclusions: The application of DIR across different imaging modalities is particularly difficult, due to differences in tissue HUs and the presence of imaging artifacts. For this reason, DIR algorithms must be validated specifically for this purpose. The developed H&N phantom is an effective tool for this purpose.
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- 2014
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22. Image simulation and a model of noise power spectra across a range of mammographic beam qualities.
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Mackenzie A, Dance DR, Diaz O, and Young KC
- Subjects
- Biophysical Phenomena, Breast Neoplasms diagnostic imaging, Female, Humans, Mammography standards, Models, Statistical, Phantoms, Imaging standards, Phantoms, Imaging statistics & numerical data, Polymethyl Methacrylate, Radiographic Image Enhancement standards, Signal Processing, Computer-Assisted, Signal-To-Noise Ratio, Mammography statistics & numerical data, Radiographic Image Enhancement methods
- Abstract
Purpose: The aim of this work is to create a model to predict the noise power spectra (NPS) for a range of mammographic radiographic factors. The noise model was necessary to degrade images acquired on one system to match the image quality of different systems for a range of beam qualities., Methods: Five detectors and x-ray systems [Hologic Selenia (ASEh), Carestream computed radiography CR900 (CRc), GE Essential (CSI), Carestream NIP (NIPc), and Siemens Inspiration (ASEs)] were characterized for this study. The signal transfer property was measured as the pixel value against absorbed energy per unit area (E) at a reference beam quality of 28 kV, Mo/Mo or 29 kV, W/Rh with 45 mm polymethyl methacrylate (PMMA) at the tube head. The contributions of the three noise sources (electronic, quantum, and structure) to the NPS were calculated by fitting a quadratic at each spatial frequency of the NPS against E. A quantum noise correction factor which was dependent on beam quality was quantified using a set of images acquired over a range of radiographic factors with different thicknesses of PMMA. The noise model was tested for images acquired at 26 kV, Mo/Mo with 20 mm PMMA and 34 kV, Mo/Rh with 70 mm PMMA for three detectors (ASEh, CRc, and CSI) over a range of exposures. The NPS were modeled with and without the noise correction factor and compared with the measured NPS. A previous method for adapting an image to appear as if acquired on a different system was modified to allow the reference beam quality to be different from the beam quality of the image. The method was validated by adapting the ASEh flat field images with two thicknesses of PMMA (20 and 70 mm) to appear with the imaging characteristics of the CSI and CRc systems., Results: The quantum noise correction factor rises with higher beam qualities, except for CR systems at high spatial frequencies, where a flat response was found against mean photon energy. This is due to the dominance of secondary quantum noise in CR. The use of the quantum noise correction factor reduced the difference from the model to the real NPS to generally within 4%. The use of the quantum noise correction improved the conversion of ASEh image to CRc image but had no difference for the conversion to CSI images., Conclusions: A practical method for estimating the NPS at any dose and over a range of beam qualities for mammography has been demonstrated. The noise model was incorporated into a methodology for converting an image to appear as if acquired on a different detector. The method can now be extended to work for a wide range of beam qualities and can be applied to the conversion of mammograms.
- Published
- 2014
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23. Calculations of stopping powers and inelastic mean free paths for 20 eV-20 keV electrons in 11 types of human tissue.
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Tan Z and Liu W
- Subjects
- Algorithms, Female, Humans, Male, Models, Biological, Optical Phenomena, Organ Specificity, Phantoms, Imaging statistics & numerical data, Polymethyl Methacrylate, Water, Electrons adverse effects, Electrons therapeutic use
- Abstract
Systematic calculations are performed for determining the stopping powers (SP) and inelastic mean free paths (IMFP) for 20 eV-20 keV electrons in 11 types of human tissue. The calculations are based on a dielectric model, including the Born-Ochkur exchange correction. The optical energy loss functions (OELF) are empirically evaluated, because of the lack of available experimental optical data for the 11 tissues under consideration. The evaluated OELFs are examined by the f-sum rule expected from the dielectric response theory, and by calculation of the mean excitation energy. The calculated SPs are compared with those for PMMA (polymethylmethacrylate, a tissue equivalent material) and liquid water. The SP and IMFP data presented here are the results for the 11 human tissues over the energy range of 20 eV-20 keV, and are of importance in radiotherapy planning and for studies of various radiation effects on human tissues., (© 2013 Elsevier Ltd. All rights reserved.)
- Published
- 2013
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24. Validation of measurement-guided 3D VMAT dose reconstruction on a heterogeneous anthropomorphic phantom.
- Author
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Opp D, Nelms BE, Zhang G, Stevens C, and Feygelman V
- Subjects
- Algorithms, Humans, Imaging, Three-Dimensional, Radiometry instrumentation, Radiometry statistics & numerical data, Radiotherapy Dosage, Phantoms, Imaging statistics & numerical data, Radiotherapy Planning, Computer-Assisted statistics & numerical data, Radiotherapy, Intensity-Modulated statistics & numerical data
- Abstract
3DVH software (Sun Nuclear Corp., Melbourne, FL) is capable of generating a volumetric patient VMAT dose by applying a volumetric perturbation algorithm based on comparing measurement-guided dose reconstruction and TPS-calculated dose to a cylindrical phantom. The primary purpose of this paper is to validate this dose reconstruction on an anthropomorphic heterogeneous thoracic phantom by direct comparison to independent measurements. The dosimetric insert to the phantom is novel, and thus the secondary goal is to demonstrate how it can be used for the hidden target end-to-end testing of VMAT treatments in lung. A dosimetric insert contains a 4 cm diameter unit-density spherical target located inside the right lung (0.21 g/cm(3) density). It has 26 slots arranged in two orthogonal directions, milled to hold optically stimulated luminescent dosimeters (OSLDs). Dose profiles in three cardinal orthogonal directions were obtained for five VMAT plans with varying degrees of modulation. After appropriate OSLD corrections were applied, 3DVH measurement-guided VMAT dose reconstruction agreed 100% with the measurements in the unit density target sphere at 3%/3 mm level (composite analysis) for all profile points for the four less-modulated VMAT plans, and for 96% of the points in the highly modulated C-shape plan (from TG-119). For this latter plan, while 3DVH shows acceptable agreement with independent measurements in the unit density target, in the lung disagreement with experiment is relatively high for both the TPS calculation and 3DVH reconstruction. For the four plans excluding the C-shape, 3%/3 mm overall composite analysis passing rates for 3DVH against independent measurement ranged from 93% to 100%. The C-shape plan was deliberately chosen as a stress test of the algorithm. The dosimetric spatial alignment hidden target test demonstrated the average distance to agreement between the measured and TPS profiles in the steep dose gradient area at the edge of the 2 cm target to be 1.0 ± 0.7, 0.3 ± 0.3, and 0.3 ± 0.3 mm for the IEC X, Y, and Z directions, respectively.
- Published
- 2013
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25. Accurate determination of CT point-spread-function with high precision.
- Author
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Kayugawa A, Ohkubo M, and Wada S
- Subjects
- Fourier Analysis, Humans, Phantoms, Imaging statistics & numerical data, Physics, Radiographic Image Enhancement methods, Tomography, X-Ray Computed statistics & numerical data
- Abstract
The measurement of modulation transfer functions (MTFs) in computed tomography (CT) is often performed by scanning a point source phantom such as a thin wire or a microbead. In these methods the region of interest (ROI) is generally placed on the scanned image to crop the point source response. The aim of the present study was to examine the effect of ROI size on MTF measurement, and to optimize the ROI size. Using a 4 multidetector-row CT, MTFs were measured by the wire and bead methods for three types of reconstruction kernels designated as 'smooth', 'standard', and 'edge-enhancement' kernels. The size of a square ROI was changed from 30 to 50 pixels (approximately 2.9 to 4.9 mm). The accuracies of the MTFs were evaluated using the verification method. The MTFs measured by the wire and bead methods were dependent on ROI size, particularly in MTF measurement for the 'edge-enhancement' kernel. MTF accuracy evaluated by the verification method changed with ROI size, and we were able to determine the optimum ROI size for each method (wire/bead) and for each kernel. Using these optimal ROI sizes, the MTF obtained by the wire method was in strong agreement with the MTF obtained by the bead method in each kernel. Our data demonstrate that the difficulties in obtaining accurate MTFs for some kernels such as edge-enhancement can be overcome by incorporating the verification method into the wire and bead methods, allowing optimization of the ROI size to accurately determine the MTF.
- Published
- 2013
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26. Differences among array, fast array, and high-definition scan modes in bone mineral density measurement at dual-energy x-ray absorptiometry on a phantom.
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Delnevo A, Bandirali M, Di Leo G, Messina C, Sconfienza LM, Aliprandi A, Ulivieri FM, and Sardanelli F
- Subjects
- Absorptiometry, Photon instrumentation, Absorptiometry, Photon statistics & numerical data, Hip diagnostic imaging, Humans, Radiation Dosage, Spine diagnostic imaging, Time Factors, Absorptiometry, Photon methods, Bone Density, Phantoms, Imaging statistics & numerical data
- Published
- 2013
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27. SNARK09 - a software package for reconstruction of 2D images from 1D projections.
- Author
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Klukowska J, Davidi R, and Herman GT
- Subjects
- Computer Graphics, Computer Simulation, Diagnostic Imaging statistics & numerical data, Humans, Phantoms, Imaging statistics & numerical data, Positron-Emission Tomography statistics & numerical data, Tomography, X-Ray Computed statistics & numerical data, User-Computer Interface, Algorithms, Image Processing, Computer-Assisted statistics & numerical data, Software
- Abstract
The problem of reconstruction of slices and volumes from 1D and 2D projections has arisen in a large number of scientific fields (including computerized tomography, electron microscopy, X-ray microscopy, radiology, radio astronomy and holography). Many different methods (algorithms) have been suggested for its solution. In this paper we present a software package, SNARK09, for reconstruction of 2D images from their 1D projections. In the area of image reconstruction, researchers often desire to compare two or more reconstruction techniques and assess their relative merits. SNARK09 provides a uniform framework to implement algorithms and evaluate their performance. It has been designed to treat both parallel and divergent projection geometries and can either create test data (with or without noise) for use by reconstruction algorithms or use data collected by another software or a physical device. A number of frequently-used classical reconstruction algorithms are incorporated. The package provides a means for easy incorporation of new algorithms for their testing, comparison and evaluation. It comes with tools for statistical analysis of the results and ten worked examples., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2013
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28. Distributed reconstruction via alternating direction method.
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Wang L, Cai A, Zhang H, Yan B, Li L, and Hu G
- Subjects
- Algorithms, Humans, Linear Models, Phantoms, Imaging statistics & numerical data, Radiographic Image Interpretation, Computer-Assisted methods, Tomography, X-Ray Computed statistics & numerical data
- Abstract
With the development of compressive sensing theory, image reconstruction from few-view projections has received considerable research attentions in the field of computed tomography (CT). Total-variation- (TV-) based CT image reconstruction has been shown to be experimentally capable of producing accurate reconstructions from sparse-view data. In this study, a distributed reconstruction algorithm based on TV minimization has been developed. This algorithm is very simple as it uses the alternating direction method. The proposed method can accelerate the alternating direction total variation minimization (ADTVM) algorithm without losing accuracy.
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- 2013
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29. Dedicated phantom materials for spectral radiography and CT.
- Author
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Shikhaliev PM
- Subjects
- Adipose Tissue diagnostic imaging, Biophysical Phenomena, Body Water diagnostic imaging, Bone and Bones diagnostic imaging, Calcium, Connective Tissue diagnostic imaging, Contrast Media, Gold, Humans, Iodine, Models, Theoretical, Phantoms, Imaging standards, Phantoms, Imaging statistics & numerical data, Radiography, Tomography, X-Ray Computed
- Abstract
As x-ray imaging technology moves from conventional radiography and computed tomography (CT) to spectral radiography and CT, dedicated phantom materials are needed for spectral imaging. The spectral phantom materials should accurately represent the energy-dependent mass-attenuation coefficients of different types of tissues. Although tissue-equivalent phantom materials were previously developed for CT and radiation therapy applications, these materials are suboptimal for spectral radiography and CT; they are not compatible with contrast agents, do not represent many of the tissue types and do not provide accurate values of attenuation characteristics of tissue. This work provides theoretical framework and a practical method for developing tissue-equivalent spectral phantom materials with a required set of parameters. The samples of the tissue-equivalent spectral phantom materials were developed, tested and characterized. The spectral phantom materials were mixed with iodine, gold and calcium contrast agents and evaluated. The materials were characterized by CT imaging and x-ray transmission experiments. The fabricated materials had nearly identical densities, mass attenuation coefficients, effective atomic numbers and electron densities as compared to corresponding tissue materials presented in the ICRU-44 report. The experimental results have shown good volume uniformity and inter-sample uniformity (repeatability of sample fabrication) of the fabricated materials. The spectral phantom materials were fabricated under laboratory conditions from readily available and inexpensive components. It was concluded that the presented theoretical framework and fabrication method of dedicated spectral phantom materials could be useful for researchers and developers working in the new area of spectral radiography and CT. Independently, the results could also be useful for other applications, such as radiation therapy., (© 2012 Institute of Physics and Engineering in Medicine)
- Published
- 2012
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30. Internal scatter, the unavoidable major component of the peripheral dose in photon-beam radiotherapy.
- Author
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Chofor N, Harder D, Willborn KC, and Poppe B
- Subjects
- Biophysical Phenomena, Computer Simulation, Humans, Models, Biological, Monte Carlo Method, Phantoms, Imaging statistics & numerical data, Scattering, Radiation, Photons therapeutic use, Radiotherapy, Conformal adverse effects, Radiotherapy, Conformal statistics & numerical data
- Abstract
In clinical photon beams, the dose outside the geometrical field limits is produced by photons originating from (i) head leakage, (ii) scattering at the beam collimators and the flattening filter (head scatter) and (iii) scattering from the directly irradiated region of the patient or phantom (internal scatter). While the first two components can be modified, e.g. by reinforcement of shielding components or by re-modeling the filter system, internal scatter remains an unavoidable contributor to the peripheral dose. Its relative magnitude compared to the other components, its numerical variation with beam energy, field size and off-axis distance as well as its spectral distribution are evaluated in this study. We applied a detailed Monte Carlo (MC) model of our 6/15 MV Siemens Primus linear accelerator beam head, provided with ideal head leakage shielding conditions (multi-leaf collimator without gaps) to assess the head scatter contribution. Experimental values obtained under real shielding conditions were used to evaluate the head leakage contribution. It was found that the MC-computed internal scatter doses agree with the results of our previous measurements, that internal scatter is the major contributor to the peripheral dose in the near periphery while head leakage prevails in the far periphery, and that the lateral decline of the internal scatter dose can be represented by the sum of two exponentials, with an asymptotic tenth value of 18 to 19 cm. Internal scatter peripheral doses from various elementary beams are additive, so that their sum increases approximately in proportion with field size. The ratio between normalized internal scatter doses at 6 and 15 MV is approximately 2:1. The energy fluence spectra of the internal scatter component at all points of interest outside the field have peaks near 500 keV. The fact that the energy-shifted internal scatter constitutes the major contributor to the dose in the near periphery has a general bearing for dosimetry, i.e. for energy-dependent detector responses and dose conversion factors, for the relative biological effectiveness and for second primary malignancy risk estimates in the peripheral region., (© 2012 Institute of Physics and Engineering in Medicine)
- Published
- 2012
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31. Hybrid computational phantoms representing the reference adult male and adult female: construction and applications for retrospective dosimetry.
- Author
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Hurtado JL, Lee C, Lodwick D, Goede T, Williams JL, and Bolch WE
- Subjects
- Adolescent, Adult, Female, Health Physics, Humans, Imaging, Three-Dimensional statistics & numerical data, Male, Models, Anatomic, Models, Theoretical, Radiation Dosage, Reference Values, Retrospective Studies, Tomography, X-Ray Computed, Phantoms, Imaging statistics & numerical data, Radiometry statistics & numerical data
- Abstract
Currently, two classes of computational phantoms have been developed for dosimetry calculation: (1) stylized (or mathematical) and (2) voxel (or tomographic) phantoms describing human anatomy through mathematical surface equations and 3D voxel matrices, respectively. Mathematical surface equations in stylized phantoms are flexible, but the resulting anatomy is not as realistic. Voxel phantoms display far better anatomical realism, but they are limited in terms of their ability to alter organ shape, position, and depth, as well as body posture. A new class of computational phantoms called hybrid phantoms takes advantage of the best features of stylized and voxel phantoms-flexibility and anatomical realism, respectively. In the current study, hybrid computational phantoms representing the adult male and female reference anatomy and anthropometry are presented. These phantoms serve as the starting framework for creating patient or worker sculpted whole-body phantoms for retrospective dose reconstruction. Contours of major organs and tissues were converted or segmented from computed tomography images of a 36-y-old Korean volunteer and a 25-y-old U.S. female patient, respectively, with supplemental high-resolution CT images of the cranium. Polygon mesh models for the major organs and tissues were reconstructed and imported into Rhinoceros™ for non-uniform rational B-spline (NURBS) surface modeling. The resulting NURBS/polygon mesh models representing body contour and internal anatomy were matched to anthropometric data and reference organ mass data provided by Centers for Disease Control and Prevention and International Commission on Radiation Protection, respectively. Finally, two hybrid adult male and female phantoms were completed where a total of eight anthropometric data categories were matched to standard values within 4% and organ volumes matched to ICRP data within 1% with the exception of total skin. The hybrid phantoms were voxelized from the NURBS phantoms at resolutions of 0.158 × 0.158 × 0.158 cm and 0.126 × 0.126 × 0.126 cm for the male and female, respectively. To highlight the flexibility of the hybrid phantoms, graphical displays are given of (1) underweight and overweight adult male phantoms, (2) a sitting position for the adult female phantom, and (3) extraction and higher-resolution voxelization of the small intestine for localized dosimetry of mucosal and stem cell layers. These phantoms are used to model radioactively contaminated individuals and to then assess time-dependent detector count rate thresholds corresponding to 50, 250, and 500 mSv effective dose, as might be needed during in-field radiological triage by first responders or first receivers.
- Published
- 2012
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32. An efficient direct volume rendering approach for dichromats.
- Author
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Chen W, Chen W, and Bao H
- Subjects
- Algorithms, Color, Databases, Factual statistics & numerical data, Humans, Imaging, Three-Dimensional statistics & numerical data, Phantoms, Imaging statistics & numerical data, User-Computer Interface, Color Vision Defects, Computer Graphics
- Abstract
Color vision deficiency (CVD) affects a high percentage of the population worldwide. When seeing a volume visualization result, persons with CVD may be incapable of discriminating the classification information expressed in the image if the color transfer function or the color blending used in the direct volume rendering is not appropriate. Conventional methods used to address this problem adopt advanced image recoloring techniques to enhance the rendering results frame-by-frame; unfortunately, problematic perceptual results may still be generated. This paper proposes an alternative solution that complements the image recoloring scheme by reconfiguring the components of the direct volume rendering (DVR) pipeline. Our approach optimizes the mapped colors of a transfer function to simulate CVD-friendly effect that is generated by applying the image recoloring to the results with the initial transfer function. The optimization process has a low computational complexity, and only needs to be performed once for a given transfer function. To achieve detail-preserving and perceptually natural semi-transparent effects, we introduce a new color composition mode that works in the color space of dichromats. Experimental results and a pilot study demonstrates that our approach can yield dichromats-friendly and consistent volume visualization in real-time., (© 2011 IEEE)
- Published
- 2011
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33. Using the NEMA NU 4 PET image quality phantom in multipinhole small-animal SPECT.
- Author
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Harteveld AA, Meeuwis AP, Disselhorst JA, Slump CH, Oyen WJ, Boerman OC, and Visser EP
- Subjects
- Animals, Diphosphonates, Mice, Mice, Inbred BALB C, Mice, Nude, Phantoms, Imaging statistics & numerical data, Positron-Emission Tomography statistics & numerical data, Radiopharmaceuticals, Technetium, Tomography, Emission-Computed, Single-Photon statistics & numerical data, Whole Body Imaging standards, Whole Body Imaging statistics & numerical data, Phantoms, Imaging standards, Positron-Emission Tomography standards, Tomography, Emission-Computed, Single-Photon standards
- Abstract
Unlabelled: Several commercial small-animal SPECT scanners using multipinhole collimation are presently available. However, generally accepted standards to characterize the performance of these scanners do not exist. Whereas for small-animal PET, the National Electrical Manufacturers Association (NEMA) NU 4 standards have been defined in 2008, such standards are still lacking for small-animal SPECT. In this study, the image quality parameters associated with the NEMA NU 4 image quality phantom were determined for a small-animal multipinhole SPECT scanner., Methods: Multiple whole-body scans of the NEMA NU 4 image quality phantom of 1-h duration were performed in a U-SPECT-II scanner using (99m)Tc with activities ranging between 8.4 and 78.2 MBq. The collimator contained 75 pinholes of 1.0-mm diameter and had a bore diameter of 98 mm. Image quality parameters were determined as a function of average phantom activity, number of iterations, postreconstruction spatial filter, and scatter correction. In addition, a mouse was injected with (99m)Tc-hydroxymethylene diphosphonate and was euthanized 6.5 h after injection. Multiple whole-body scans of this mouse of 1-h duration were acquired for activities ranging between 3.29 and 52.7 MBq., Results: An increase in the number of iterations was accompanied by an increase in the recovery coefficients for the small rods (RC(rod)), an increase in the noise in the uniform phantom region, and a decrease in spillover ratios for the cold-air- and water-filled scatter compartments (SOR(air) and SOR(wat)). Application of spatial filtering reduced image noise but lowered RC(rod). Filtering did not influence SOR(air) and SOR(wat). Scatter correction reduced SOR(air) and SOR(wat). The effect of total phantom activity was primarily seen in a reduction of image noise with increasing activity. RC(rod), SOR(air), and SOR(wat) were more or less constant as a function of phantom activity. The relation between acquisition and reconstruction settings and image quality was confirmed in the (99m)Tc-hydroxymethylene diphosphonate mouse scans., Conclusion: Although developed for small-animal PET, the NEMA NU 4 image quality phantom was found to be useful for small-animal SPECT as well, allowing for objective determination of image quality parameters and showing the trade-offs between several of these parameters on variation of acquisition and reconstruction settings.
- Published
- 2011
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34. Development of 5- and 10-year-old pediatric phantoms based on polygon mesh surfaces.
- Author
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Lima VJ, Cassola VF, Kramer R, Lira CA, Khoury HJ, and Vieira JW
- Subjects
- Child, Child, Preschool, Computer Simulation, Female, Humans, Imaging, Three-Dimensional, Male, Models, Anatomic, Radiometry, Surface Properties, X-Ray Microtomography, Phantoms, Imaging statistics & numerical data, Radiation Protection statistics & numerical data
- Abstract
Purpose: The purpose of this study is the development of reference pediatric phantoms for 5- and 10-year-old children to be used for the calculation of organ and tissue equivalent doses in radiation protection., Methods: The study proposes a method for developing anatomically highly sophisticated pediatric phantoms without using medical images. The 5- and 10-year-old male and female phantoms presented here were developed using 3D modeling software applied to anatomical information taken from atlases and textbooks. The method uses polygon mesh surfaces to model body contours, the shape of organs as well as their positions, and orientations in the human body. Organ and tissue masses comply with the corresponding data given by the International Commission on Radiological Protection (ICRP) for the 5- and 10-year-old reference children. Bones were segmented into cortical bone, spongiosa, medullary marrow, and cartilage to allow for the use of micro computer tomographic (microCT) images of trabecular bone for skeletal dosimetry., Results: The four phantoms, a male and a female for each age, and their organs are presented in 3D images and their organ and tissue masses in tables which show the compliance of the ICRP reference values. Dosimetric data, calculated for the reference pediatric phantoms by Monte Carlo methods were compared with corresponding data from adult mesh phantoms and pediatric stylized phantoms. The comparisons show reasonable agreement if the anatomical differences between the phantoms are properly taken into account., Conclusions: Pediatric phantoms were developed without using medical images of patients or volunteers for the first time. The models are reference phantoms, suitable for regulatory dosimetry, however, the 3D modeling method can also be applied to medical images to develop patient-specific phantoms.
- Published
- 2011
- Full Text
- View/download PDF
35. Graphics processing unit parallel accelerated solution of the discrete ordinates for photon transport in biological tissues.
- Author
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Peng K, Gao X, Qu X, Ren N, Chen X, He X, Wang X, Liang J, and Tian J
- Subjects
- Animals, Computer Graphics, Computer Simulation, Mice, Models, Biological, Phantoms, Imaging statistics & numerical data, Scattering, Radiation, Software Design, Optical Phenomena, Photons
- Abstract
As a widely used numerical solution for the radiation transport equation (RTE), the discrete ordinates can predict the propagation of photons through biological tissues more accurately relative to the diffusion equation. The discrete ordinates reduce the RTE to a serial of differential equations that can be solved by source iteration (SI). However, the tremendous time consumption of SI, which is partly caused by the expensive computation of each SI step, limits its applications. In this paper, we present a graphics processing unit (GPU) parallel accelerated SI method for discrete ordinates. Utilizing the calculation independence on the levels of the discrete ordinate equation and spatial element, the proposed method reduces the time cost of each SI step by parallel calculation. The photon reflection at the boundary was calculated based on the results of the last SI step to ensure the calculation independence on the level of the discrete ordinate equation. An element sweeping strategy was proposed to detect the calculation independence on the level of the spatial element. A GPU parallel frame called the compute unified device architecture was employed to carry out the parallel computation. The simulation experiments, which were carried out with a cylindrical phantom and numerical mouse, indicated that the time cost of each SI step can be reduced up to a factor of 228 by the proposed method with a GTX 260 graphics card., (© 2011 Optical Society of America)
- Published
- 2011
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- View/download PDF
36. Strain measurement from 3D micro-CT images of a breast-mimicking phantom.
- Author
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Lee SY, Kim GW, Han BH, and Cho MH
- Subjects
- Computer Simulation, Elasticity Imaging Techniques statistics & numerical data, Female, Humans, Imaging, Three-Dimensional, Mammography statistics & numerical data, X-Ray Microtomography statistics & numerical data, Breast physiology, Elasticity, Phantoms, Imaging statistics & numerical data
- Abstract
Strain distribution in compressed tissues gives information about elasticity of the tissues. We have measured strain from two sets of 3D micro-CT images of a breast-mimicking phantom; one obtained without compressing the phantom and the other with compressing it. To measure strain, we first calculated compression-induced displacements of high-intensity feature patterns in the image. In measuring displacement of a pixel of interest, we searched the pixel in the compressed-phantom image, whose surrounding resembles the uncompressed-phantom image most closely, using the image correlation technique. From the displacement data, we calculated average strain at a region of interest. With the calculated average strains, we could distinguish the hard inclusion in the phantom which was not distinguishable from the background body of the phantom in the ordinary micro-CT images. The calculated strains account for stiffness of the tissue of interest, one of the important parameters for diagnosing malignant tissues. We present experimental results of the displacement and strain measurement along with FEM analysis results., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Published
- 2011
- Full Text
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37. Doses to internal organs for various breast radiation techniques--implications on the risk of secondary cancers and cardiomyopathy.
- Author
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Pignol JP, Keller BM, and Ravi A
- Subjects
- Cardiomyopathies epidemiology, Databases, Factual, Female, Humans, Neoplasms, Radiation-Induced etiology, Neoplasms, Second Primary epidemiology, Phantoms, Imaging statistics & numerical data, Radiation Injuries epidemiology, Radiation Injuries etiology, Radiotherapy adverse effects, Radiotherapy Dosage, Retrospective Studies, Risk Factors, Breast Neoplasms radiotherapy, Carcinoma radiotherapy, Cardiomyopathies etiology, Neoplasms, Second Primary etiology, Organs at Risk radiation effects, Radiotherapy methods
- Abstract
Background: Breast cancers are more frequently diagnosed at an early stage and currently have improved long term outcomes. Late normal tissue complications induced by adjuvant radiotherapy like secondary cancers or cardiomyopathy must now be avoided at all cost. Several new breast radiotherapy techniques have been developed and this work aims at comparing the scatter doses of internal organs for those techniques., Methods: A CT-scan of a typical early stage left breast cancer patient was used to describe a realistic anthropomorphic phantom in the MCNP Monte Carlo code. Dose tally detectors were placed in breasts, the heart, the ipsilateral lung, and the spleen. Five irradiation techniques were simulated: whole breast radiotherapy 50 Gy in 25 fractions using physical wedge or breast IMRT, 3D-CRT partial breast radiotherapy 38.5 Gy in 10 fractions, HDR brachytherapy delivering 34 Gy in 10 treatments, or Permanent Breast 103Pd Seed Implant delivering 90 Gy., Results: For external beam radiotherapy the wedge compensation technique yielded the largest doses to internal organs like the spleen or the heart, respectively 2,300 mSv and 2.7 Gy. Smaller scatter dose are induced using breast IMRT, respectively 810 mSv and 1.1 Gy, or 3D-CRT partial breast irradiation, respectively 130 mSv and 0.7 Gy. Dose to the lung is also smaller for IMRT and 3D-CRT compared to the wedge technique. For multicatheter HDR brachytherapy a large dose is delivered to the heart, 3.6 Gy, the spleen receives 1,171 mSv and the lung receives 2,471 mSv. These values are 44% higher in case of a balloon catheter. In contrast, breast seeds implant is associated with low dose to most internal organs., Conclusions: The present data support the use of breast IMRT or virtual wedge technique instead of physical wedges for whole breast radiotherapy. Regarding partial breast irradiation techniques, low energy source brachytherapy and external beam 3D-CRT appear safer than 192Ir HDR techniques.
- Published
- 2011
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38. Assessing the clinical utility of quantitative computed tomography with a routinely used diagnostic computed tomography scanner in a cancer center.
- Author
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Hui SK, Weir VJ, Brown K, and Froelich J
- Subjects
- Body Weights and Measures, Bone Density, Combined Modality Therapy adverse effects, Humans, Osteoporosis etiology, Phantoms, Imaging statistics & numerical data, Radiation Dosage, Radiologic Health, Tomography Scanners, X-Ray Computed standards, Tomography Scanners, X-Ray Computed statistics & numerical data, Tomography, X-Ray Computed statistics & numerical data, Cancer Care Facilities standards, Cancer Care Facilities supply & distribution, Osteoporosis diagnostic imaging, Phantoms, Imaging standards, Tomography, X-Ray Computed instrumentation
- Abstract
The purpose of this study was to characterize quantitative computed tomography (QCT) in our multi-detector computed tomography (MDCT) scanner with regard to the influence of the QCT phantom on dose and the influence of varying mA and CIRS phantom size on bone mineral density (BMD) measurements. We accomplish this by scanning a commercially available QCT phantom and a corresponding quality assurance phantom. To assess the feasibility of having the QCT phantom in place while patients are being scanned, we measured radiation dose difference in a CT body phantom with and without the QCT phantom on the CT table and also, with and without the use of dose modulation programs. We also analyzed reconstructed QCT phantom images with the manufacturer's software to measure BMD. Although patient characteristics may be different, leading to different mA values, the influence of the QCT phantom on the dose to patients was minimal when compared with doses measured without the phantom in place. Average BMD measurements were not significantly affected by varying mA, for a fixed-size phantom. The average BMD exhibited a weak dependence on computerized imaging reference systems (CIRS) torso phantom size, with a propensity for decreasing BMD with increasing size. Measurement precision was unaffected by varying CIRS size. Having the ability to measure bone density as part of the routine management of cancer patients, with no added cost, time, or radiation dose, will allow for the prospective evaluation of bone mineral changes. We believe that this ability will facilitate the detection of abnormal bone loss and will lead to better management of this loss and, thus, reduce the complications and associated morbidity in these cancer survivors., (Copyright © 2011 The International Society for Clinical Densitometry. Published by Elsevier Inc. All rights reserved.)
- Published
- 2011
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39. Monte Carlo simulation of the effect of miniphantom on in-air output ratio.
- Author
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Li J and Zhu TC
- Subjects
- Air, Biophysical Phenomena, Computer Simulation, Humans, Monte Carlo Method, Particle Accelerators statistics & numerical data, Photons therapeutic use, Radiotherapy, Conformal statistics & numerical data, Phantoms, Imaging statistics & numerical data, Radiotherapy Planning, Computer-Assisted statistics & numerical data
- Abstract
Purpose: The aim of the study was to quantify the effect of miniphantoms on in-air output ratio measurements, i.e., to determine correction factors for in-air output ratio., Methods: Monte Carlo (MC) simulations were performed to simulate in-air output ratio measurements by using miniphantoms made of various materials (PMMA, graphite, copper, brass, and lead) and with different longitudinal thicknesses or depths (2-30 g/cm2) in photon beams of 6 and 15 MV, respectively, and with collimator settings ranging from 3 x 3 to 40 x 40 cm2. EGSnrc and BEAMnrc (2007) software packages were used. Photon energy spectra corresponding to the collimator settings were obtained from BEAMnrc code simulations on a linear accelerator and were used to quantify the components of in-air output ratio correction factors, i.e., attenuation, mass energy absorption, and phantom scatter correction factors. In-air output ratio correction factors as functions of miniphantom material, miniphantom longitudinal thickness, and collimator setting were calculated and compared to a previous experimental study., Results: The in-air output ratio correction factors increase with collimator opening and miniphantom longitudinal thickness for all the materials and for both energies. At small longitudinal thicknesses, the in-air output ratio correction factors for PMMA and graphite are close to 1. The maximum magnitudes of the in-air output ratio correction factors occur at the largest collimator setting (40 x 40 cm2) and the largest miniphantom longitudinal thickness (30 g/cm2): 1.008 +/- 0.001 for 6 MV and 1.012 +/- 0.001 for 15 MV, respectively. The MC simulations of the in-air output ratio correction factor confirm the previous experimental study., Conclusions: The study has verified that a correction factor for in-air output ratio can be obtained as a product of attenuation correction factor, mass energy absorption correction factor, and phantom scatter correction factor. The correction factors obtained in the present study can be used in studies involving in-air output ratio measurements using miniphantoms.
- Published
- 2010
- Full Text
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40. A priori fluorophore distribution estimation in fluorescence imaging through application of a segmentation process and a data fitting technique.
- Author
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Gorpas D, Yova D, and Politopoulos K
- Subjects
- Algorithms, Finite Element Analysis, Image Processing, Computer-Assisted statistics & numerical data, Phantoms, Imaging statistics & numerical data, Diagnostic Imaging methods, Fluorescence, Image Processing, Computer-Assisted methods
- Abstract
During the last few years a quite large number of fluorescence imaging applications have been reported in the literature, as one of the most challenging problems in medical imaging is to "see" a tumor embedded in tissue, which is a turbid medium. This problem has not been fully encountered yet, due to the non-linear nature of the inverse problem. In this paper, a novel method for processing the forward solver outcomes is presented. Through this technique the comparison between the simulated and the acquired data can be performed only at the region-of-interest, minimizing time-consuming pixel-to-pixel comparison. With this modus operandi a-priori information about the initial fluorophore distribution becomes available, leading to a more feasible inverse problem solution.
- Published
- 2010
- Full Text
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41. Depth scaling of solid phantom for intensity modulated radiotherapy beams.
- Author
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Fujita Y, Tohyama N, Myojoyama A, and Saitoh H
- Subjects
- Computer Simulation, Humans, Monte Carlo Method, Particle Accelerators, Photons therapeutic use, Radiometry methods, Radiotherapy Planning, Computer-Assisted, Phantoms, Imaging statistics & numerical data, Radiotherapy, Intensity-Modulated statistics & numerical data
- Abstract
To reduce the uncertainty of absorbed dose for high energy photon beams, water has been chosen as a reference material by the dosimetry protocols. However, solid phantoms are used as media for absolute dose verification of intensity modulated radiotherapy (IMRT). For the absorbed dose measurement, the fluence scaling factor is used for converting an ionization chamber reading in a solid phantom to absorbed dose to water. Furthermore the depth scaling factor is indispensable in determining the fluence scaling factor. For IMRT beams, a photon energy spectrum is varied by transmitting through a multileaf collimator and attenuating in media. However, the effects of spectral variations on depth scaling have not been clarified yet. In this study, variations of photon energy spectra were determined using the EGS Monte Carlo simulation. The depth scaling factors for commercially available solid phantoms were determined from effective mass attenuation coefficients using photon energy spectra. The results clarified the effect of spectral variation on the depth scaling and produced an accurate scaling method for IMRT beams.
- Published
- 2010
- Full Text
- View/download PDF
42. Megavoltage photon beam attenuation by carbon fiber couch tops and its prediction using correction factors.
- Author
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Hayashi N, Shibamoto Y, Obata Y, Kimura T, Nakazawa H, Hagiwara M, Hashizume CI, Mori Y, and Kobayashi T
- Subjects
- Carbon, Carbon Fiber, Carcinoma, Hepatocellular radiotherapy, Humans, Liver Neoplasms radiotherapy, Phantoms, Imaging statistics & numerical data, Radiotherapy Planning, Computer-Assisted statistics & numerical data, Radiotherapy, Conformal statistics & numerical data, Radiotherapy, High-Energy statistics & numerical data, Stereotaxic Techniques, Water, Photons therapeutic use, Radiotherapy, Conformal methods, Radiotherapy, High-Energy methods
- Abstract
The purpose of this study was to evaluate the effect of megavoltage photon beam attenuation (PBA) by couch tops and to propose a method for correction of PBA. Four series of phantom measurements were carried out. First, PBA by the exact couch top (ECT, Varian) and Imaging Couch Top (ICT, BrainLAB) was evaluated using a water-equivalent phantom. Second, PBA by Type-S system (Med-Tec), ECT and ICT was compared with a spherical phantom. Third, percentage depth dose (PDD) after passing through ICT was measured to compare with control data of PDD. Forth, the gantry angle dependency of PBA by ICT was evaluated. Then, an equation for PBA correction was elaborated and correction factors for PBA at isocenter were obtained. Finally, this method was applied to a patient with hepatoma. PBA of perpendicular beams by ICT was 4.7% on average. With the increase in field size, the measured values became higher. PBA by ICT was greater than that by Type-S system and ECT. PBA increased significantly as the angle of incidence increased, ranging from 4.3% at 180 degrees to 11.2% at 120 degrees . Calculated doses obtained by the equation and correction factors agreed quite well with the measured doses between 120 degrees and 180 degrees of angles of incidence. Also in the patient, PBA by ICT was corrected quite well by the equation and correction factors. In conclusion, PBA and its gantry angle dependency by ICT were observed. This simple method using the equation and correction factors appeared useful to correct the isocenter dose when the PBA effect cannot be corrected by a treatment planning system.
- Published
- 2010
- Full Text
- View/download PDF
43. Dosimetry parameters of the IRH10 192Ir high dose rate brachytherapy source.
- Author
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Yi CY, Chun KJ, Hah SH, Kim HM, and Lim C
- Subjects
- Air, Anisotropy, Humans, Monte Carlo Method, Phantoms, Imaging statistics & numerical data, Photons therapeutic use, Radiometry statistics & numerical data, Radiotherapy Dosage, Water, Brachytherapy statistics & numerical data, Iridium Radioisotopes therapeutic use
- Abstract
The dosimetry parameters of the IRH10 (192)Ir high dose rate brachytherapy source were obtained from the dose calculation formalism recommended in the AAPM Task Group No. 43 report using the Monte Carlo code PENELOPE. The absorbed doses to water and air originating from the photons of the IRH10 (192)Ir brachytherapy source were calculated by the collision kerma approximation. The dose rate constant was evaluated to be (1.110 +/- 0.011) cGy/h U(-1). The dose rate per unit air kerma strength around the (192)Ir IRH10 brachytherapy source and the anisotropy function were given in tables and figures.
- Published
- 2010
- Full Text
- View/download PDF
44. Motion correction based on an appropriate system matrix for statistical reconstruction of respiratory-correlated PET acquisitions.
- Author
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Fin L, Bailly P, Daouk J, and Meyer ME
- Subjects
- Algorithms, Databases, Factual, Fluorodeoxyglucose F18, Humans, Imaging, Three-Dimensional statistics & numerical data, Motion, Phantoms, Imaging statistics & numerical data, Radiopharmaceuticals, Tomography, X-Ray Computed statistics & numerical data, Image Processing, Computer-Assisted statistics & numerical data, Positron-Emission Tomography statistics & numerical data, Respiratory Mechanics physiology
- Abstract
Respiratory motion correction in positron emission tomography (PET) seeks to incorporate motion information into an image reconstruction algorithm by using the full counting statistics of an acquisition to generate a single, motion-free volume. Here, we present a motion-incorporated ordered subsets expectation maximization (MOSEM) reconstruction based on a device-dedicated tomographic projector in which each matrix element is calculated directly from the voxels' Cartesian coordinates alone. The motion is corrected by updating this projector as a function of the respiratory level. The performance of the reconstruction method was investigated with three datasets: two simulations of a transaxially or axially moving lesion on a patient acquisition and a third acquisition of a moving sphere. After the 16th sub-iteration, the normalized mean square error (NMSE, with a motionless acquisition as reference) was 0.20 for the non-corrected (ungated) image and 0.01 for the MOSEM image with transaxial motion simulation. Likewise, NMSE was 0.30 for the ungated image and 0.03 for MOSEM image with axial motion simulation. For the phantom, ungated reconstruction yielded an error of 0.78, whereas MOSEM yielded 0.43. The error reduction resulted from enhancement and reduced spreading of the moving uptake. Our results show that MOSEM reconstruction yields motion-corrected images which are similar to motionless reference images.
- Published
- 2009
- Full Text
- View/download PDF
45. A calibration phantom for direct, in vivo measurement of 241Am in the axillary lymph nodes.
- Author
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Zeman R, Lobaugh M, Spitz H, Glover S, and Hickman D
- Subjects
- Americium adverse effects, Americium pharmacokinetics, Axilla, Humans, Liver radiation effects, Lung radiation effects, Occupational Exposure, Radiation Dosage, Radiation Monitoring, Americium analysis, Lymph Nodes radiation effects, Phantoms, Imaging statistics & numerical data
- Abstract
A calibration phantom was developed at the University of Cincinnati (UC) to determine detection efficiency and estimate the quantity of activity deposited in the axillary lymph nodes of a worker who had unknowingly sustained a wound contaminated with 241Am at some distant time in the past. This paper describes how the Livermore Torso Phantom was modified for calibrating direct, in vivo measurements of 241Am deposited in the axillary lymph nodes. Modifications involved milling a pair of parallel, flat bottom, cylindrical holes into the left and right shoulders (below the humeral head) of the Livermore Torso Phantom in which solid, 1.40-cm-diameter cylindrical rods were inserted. Each rod was fabricated using a muscle tissue substitute. One end of each rod contained a precisely known quantity of Am sealed in a 1-cm-diameter, 2.54-cm-deep well to simulate the axillary lymph nodes when inserted into the modified Livermore Torso Phantom. The fixed locations for the axillary lymph nodes in the phantom were determined according to the position of the Level I and the combined Level II + III axillary lymph nodes reported in the literature. Discrete calibration measurements for 241Am in the simulated axillary lymph nodes located in the right and left sides of the thorax were performed using pairs of high-resolution germanium detectors at UC and Lawrence Livermore National Laboratory. The percent efficiency for measuring the 59.5 keV photon from Am deposited in the right and left axillary lymph nodes using a pair of 3,000 mm2 detectors is 2.60 +/- 0.03 counts gamma-1 and 5.45 +/- 0.07 counts gamma-1, respectively. Activity deposited in the right and left axillary lymph nodes was found to contribute 12.5% and 19.7%, respectively, to a lung measurement and 1.2% and 0.2%, respectively, to a liver measurement. Thus, radioactive material mobilized from a wound in a finger or hand and deposited in the axillary lymph nodes has been shown to confound results of a direct, in vivo measurement of the lungs.
- Published
- 2009
- Full Text
- View/download PDF
46. Nonlinear reconstruction of absorption and fluorescence contrast from measured diffuse transmittance and reflectance of a compressed-breast-simulating phantom.
- Author
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Ziegler R, Nielsen T, Koehler T, Grosenick D, Steinkellner O, Hagen A, Macdonald R, and Rinneberg H
- Subjects
- Algorithms, Contrast Media, Female, Fluorescence, Fluorescent Dyes, Humans, Nonlinear Dynamics, Optical Phenomena, Tomography, Optical statistics & numerical data, Breast pathology, Breast Neoplasms diagnosis, Image Processing, Computer-Assisted statistics & numerical data, Phantoms, Imaging statistics & numerical data, Tomography, Optical methods
- Abstract
We report on the nonlinear reconstruction of local absorption and fluorescence contrast in tissuelike scattering media from measured time-domain diffuse reflectance and transmittance of laser as well as laser-excited fluorescence radiation. Measurements were taken at selected source-detector offsets using slablike diffusely scattering and fluorescent phantoms containing fluorescent heterogeneities. Such measurements simulate in vivo data that would be obtained employing a scanning, time-domain fluorescence mammograph, where the breast is gently compressed between two parallel glass plates, and source and detector optical fibers scan synchronously at various source-detector offsets, allowing the recording of laser and fluorescence mammograms. The diffusion equations modeling the propagation of the laser and fluorescence radiation were solved in frequency domain by the finite element method simultaneously for several modulation frequencies using Fourier transformation and preprocessed experimental data. To reconstruct the concentration of the fluorescent contrast agent, the Born approximation including higher-order reconstructed photon densities at the excitation wavelength was used. Axial resolution was determined that can be achieved by various detection schemes. We show that remission measurements increase the depth resolution significantly.
- Published
- 2009
- Full Text
- View/download PDF
47. Monte-Carlo simulation of uncertainty in the estimation of 125I in the thyroid.
- Author
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Bhati S and Patni HK
- Subjects
- Computer Simulation, Humans, India, Monte Carlo Method, Occupational Exposure, Phantoms, Imaging statistics & numerical data, Radiation Monitoring statistics & numerical data, Software, Thyroid Gland anatomy & histology, Iodine Radioisotopes adverse effects, Iodine Radioisotopes analysis, Thyroid Gland radiation effects
- Abstract
At the Bhabha Atomic Research Centre, a thin (76 mm diameter x 2 mm thickness) NaI (Tl) detector is used for the assessment of (125)I in the thyroid of the radiation workers engaged in the preparation of radio-immunoassay kits. The detector was calibrated using a REMCAL (radiation equivalent manikin calibration) phantom with a known amount of the (125)I activity filled in its thyroidal cavity. Since (125)I emits low-energy photons ranging from 27 to 35.4 keV, its detection efficiency depends on several parameters such as neck-to-detector distance, detector size, unknown tissue thickness overlying (OTT) the thyroid and the shape and size of the thyroid. To account for uncertainties introduced by these factors in the estimation of (125)I, a computer program based on the Monte Carlo photon transport techniques was developed. The program simulates the detector response and the corresponding detection efficiencies using two thyroid models: (1) revised MIRD head phantom and (2) Ulanvosky model. The program has been validated with experimental measurements carried out using a REMCAL phantom. The computed values of uncertainties due to placement errors (+/-0.5 cm) for different detector sizes, differences in the OTT of the thyroid (0.6-2.0 cm) and different thyroid shapes are presented in this paper. The computed values of the calibration factors, determined for the revised MIRD phantom, varied from 5.23 to 1.06 x 10(-2) counts per photon for detector distance of 3-12 cm and from 7.53 to 3.66 x 10(-2) counts per photon for OTT varying from 0.6 to 2.0 cm keeping the detector at a distance of 3 cm. This study shows that the variations in OTT constitute a major source of uncertainty. The computed uncertainties due to various parameters should be taken into account while estimating the thyroidal burden of (125)I in the radiation workers. The feasibility of using coincidence method for absolute determination of the (125)I activity in the thyroid is also discussed in this paper.
- Published
- 2009
- Full Text
- View/download PDF
48. Evaluation of radiation doses from MDCT-imaging in otolaryngology.
- Author
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Yamauchi-Kawaura C, Fujii K, Aoyama T, Yamauchi M, and Koyama S
- Subjects
- Humans, Phantoms, Imaging statistics & numerical data, Otorhinolaryngologic Diseases diagnostic imaging, Radiation Dosage, Radiometry statistics & numerical data, Tomography, X-Ray Computed statistics & numerical data
- Abstract
The purpose of this study was to clarify patient doses in the current otolaryngological multi-detector row computed tomography (MDCT) examinations. Patient doses were measured with an in-phantom dosimetry system which was composed of 48 photodiode dosimeters embedded within an anthropomorphic phantom. Organ and effective doses were evaluated according to the International Commission on Radiological Protection Publication 103. In neck CT, doses for salivary glands and for thyroid were high, 7.6-29.9 and 13.4-60.3 mGy, respectively. In sinus CT, brain and lens doses were high, 7.6-24.6 and 10.6-32.0 mGy, respectively, and in inner ear CT, lens dose was 8.0-35.3 mGy. Effective doses were 1.8-6.6 mSv in neck CT, 0.5-0.9 mSv in sinus CT and 0.3-0.6 mSv in inner ear CT. The present dose data would be used to estimate radiation risks for patients undergoing otolaryngological MDCT examinations.
- Published
- 2009
- Full Text
- View/download PDF
49. Dose imaging in a thorax phantom with lung-equivalent volume at the epithermal neutron beam of LVR-15 reactor.
- Author
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Gambarini G, Vanossi E, Bartesaghi G, Carrara M, Mariani M, Negri A, Burian J, Viererbl L, Klupak V, and Rejchrt J
- Subjects
- Boron therapeutic use, Czech Republic, Gels, Humans, Isotopes therapeutic use, Nuclear Reactors, Photons therapeutic use, Radiation-Sensitizing Agents therapeutic use, Radiometry instrumentation, Radiometry statistics & numerical data, Thorax, Boron Neutron Capture Therapy instrumentation, Boron Neutron Capture Therapy statistics & numerical data, Fast Neutrons therapeutic use, Lung Neoplasms radiotherapy, Phantoms, Imaging statistics & numerical data, Radiotherapy Planning, Computer-Assisted statistics & numerical data
- Abstract
A thorax phantom has been designed, consisting of PMMA and PE plates containing a cavity filled with a laboratory-made lung-substitute. Fricke-gel dosimeters have been placed in the lung-substitute volume, and the phantom has been irradiated at the epithermal column of LVR-15 reactor. Absorbed dose images have been obtained for both gamma radiation and charged particles emitted in the (10)B reactions with thermal neutrons. Measurements with thermoluminescence dosimeters (TLDs) and Monte Carlo (MC) calculations have been performed too, in order to attain inter-comparison of results.
- Published
- 2009
- Full Text
- View/download PDF
50. Evaluation of all dose components in the LVR-15 reactor epithermal neutron beam using Fricke gel dosimeter layers.
- Author
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Bartesaghi G, Burian J, Gambarini G, Marek M, Negri A, and Viererbl L
- Subjects
- Animals, Czech Republic, Ferrous Compounds, Gelatin, Humans, Monte Carlo Method, Solutions, Swine, Thermoluminescent Dosimetry statistics & numerical data, Water, Boron Neutron Capture Therapy statistics & numerical data, Fast Neutrons therapeutic use, Nuclear Reactors statistics & numerical data, Phantoms, Imaging statistics & numerical data, Radiometry instrumentation, Radiometry statistics & numerical data, Radiotherapy Planning, Computer-Assisted statistics & numerical data
- Abstract
Fricke gel dosimeters in the form of layers are suitable to reconstruct bidimensional distributions of the absorbed dose; in accordance with their chemical composition and applying suitably developed algorithms, they can provide dose images of the different radiation components in a BNCT field. After the description of the applied method, this work presents the results obtained at the epithermal column of the BNCT facility at the NRI in Rez (CZ). The measured dose distributions are shown in comparison with data taken by means of other dosimeters thermoluminescence dosimeters (TLDs) and with calculations carried out with the Monte Carlo code MCNP5. The agreement with the results obtained by means of the different techniques is satisfying.
- Published
- 2009
- Full Text
- View/download PDF
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