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BACKGROUND: Recently, deep learning reconstruction (DLR) technology aiming to improve image quality with minimal radiation dose has been applied not only to pediatric scans, but also to computed tomography angiography (CTA). OBJECTIVE: To evaluate image quality characteristics of filtered back projection (FBP), hybrid iterative reconstruction [Adaptive Iterative Dose Reduction 3D (AIDR 3D)], and DLR (AiCE) using different iodine concentrations and scan parameters. METHODS: Phantoms with eight iodine concentrations (ranging from 1.2 to 25.9 mg/mL) located at the edge of a cylindrical water phantom with a diameter of 19 cm were scanned. Data were reconstructed with FBP, AIDR 3D, and AiCE using various scan parameters of tube current and voltage using a 320 row-detector CT scanner. Data obtained using different reconstruction techniques were quantitatively compared by analyzing Hounsfield units (HU), noise, and contrast-to-noise ratios (CNRs). RESULTS: HU values of FBP and AIDR 3D were constant even when the iodine concentration was changed, whereas AiCE showed the highest HU value when the iodine concentration was low, but the HU value reversed when the iodine concentration exceeded a certain value. In the AIDR 3D and AiCE, the noise decreased as the tube current increased, and the change in noise when the iodine concentration was inconsistent. AIDR 3D and AiCE yielded better noise reduction rates than with FBP at a low tube current. The noise reduction rate of AIDR 3D and AiCE compared to that of FBP showed characteristics ranging from 7% to 35%, and the noise reduction rate of AiCE compared to that of AIDR 3D ranged from 2.0% to 13.3%. CONCLUSIONS: The evaluated reconstruction techniques showed different image quality characteristics (HU value, noise, and CNR) according to dose and scan parameters, and users must consider these results and characteristics before performing patient scans.

Objective. The purpose of this study is to assess its human images and its unique capabilities such as the ‘on demand’ higher spatial resolution and multi-spectral imaging of photon-counting-detector (PCD)-CT. Approach. In this study, the FDA 510(k) cleared mobile PCD-CT (OmniTom Elite) was used. To this end, we imaged internationally certified CT phantoms and a human cadaver head to evaluate the feasibility of high resolution (HR) and multi-energy imaging. We also demonstrate the performance of PCD-CT via first-in-human imaging by scanning three human volunteers. Main results. At the 5 mm slice thickness, routinely used in diagnostic head CT, the first human PCD-CT images were diagnostically equivalent to the EID-CT scanner. The HR acquisition mode of PCD-CT achieved a resolution of 11 line-pairs (lp)/cm as compared to 7 lp cm−1 using the same kernel (posterior fossa-kernel) in the standard acquisition mode of EID-CT. For the quantitative multi-energy CT performance, the measured CT numbers in virtual mono-energetic images (VMI) of iodine inserts in the Gammex Multi-Energy CT phantom (model 1492, Sun Nuclear Corporation, USA) matched the manufacturer reference values with mean percent error of 3.25%. Multi-energy decomposition with PCD-CT demonstrated the separation and quantification of iodine, calcium, and water. Significance. PCD-CT can achieve multi-resolution acquisition modes without physically changing the CT detector. It can provide superior spatial resolution compared with the standard acquisition mode the conventional mobile EID-CT. Quantitative spectral capability of PCD-CT can provide accurate, simultaneous multi-energy images for material decomposition and VMI generation using a single exposure.

In this study, preclinical experiments were performed with an in-house developed prototypal photon-counting detector computed tomography (PCD CT) system. The performance of the system was compared with the conventional energy-integrating detector (EID)-based CT, concerning the basic image quality biomarkers and the respective capacities for material separation. The pre- and the post-contrast axial images of a canine brain captured by the PCD CT and EID CT systems were found to be visually similar. Multi-energy images were acquired using the PCD CT system, and machine learning-based material decomposition was performed to segment the white and gray matters for the first time in soft tissue segmentation. Furthermore, to accommodate clinical applications that require high resolution acquisitions, a small, native, high-resolution (HR) detector was implemented on the PCD CT system, and its performance was evaluated based on animal experiments. The HR acquisition mode improved the spatial resolution and delineation of the fine structures in the canine’s nasal turbinates compared to the standard mode. Clinical applications that rely on high-spatial resolution expectedly will also benefit from this resolution-enhancing function. The results demonstrate the potential impact on the brain tissue segmentation, improved detection of the liver tumors, and capacity to reconstruct high-resolution images both preclinically and clinically.

Metal artifacts are considered a major challenge in computed tomography (CT) as these adversely affect the diagnosis and treatment of patients. Several approaches have been developed to address this problem. The present study explored the clinical potential of a novel photon-counting detector (PCD) CT system in reducing metal artifacts in head CT scans. In particular, we studied the recovery of an oral tumor region located under metal artifacts after correction. Three energy thresholds were used to group data into three bins (bin 1: low-energy, bin 2: middle-energy, and bin 3: high-energy) in the prototype PCD CT system. Three types of physical phantoms were scanned on the prototype PCD CT system. First, we assessed the accuracy of iodine quantification using iodine phantoms at varying concentrations. Second, we evaluated the performance of material decomposition (MD) and virtual monochromatic images (VMIs) using a multi-energy CT phantom. Third, we designed an ATOM phantom with metal insertions to verify the effect of the proposed metal artifact reduction. In particular, we placed an insertion-mimicking an iodine-enhanced oral tumor in the beam path of metallic objects. Normalized metal artifact reduction (NMAR) was performed for each energy bin image, followed by an image-based MD and VMI reconstruction. Image quality was analyzed quantitatively by contrast-to-noise ratio (CNR) measurements. The results of iodine quantification showed a good match between the true and measured iodine concentrations. Furthermore, as expected, the contrast between iodine and the surrounding material was higher in bin 1 image than in bin 3 image. On the other hand, the bin 3 image of the ATOM phantom showed fewer metal artifacts than the bin 1 image because of the higher photon energy. The result of quantitative assessment demonstrated that the 40-keV VMI (CNR: 20.6 ± 1.2) with NMAR and MD remarkably increased the contrast of the iodine-enhanced region compared with that of the conventional images (CNR: 10.4 ± 0.5) having 30 to 140 keV energy levels. The PCD-based multi-energy CT imaging has immense potential to maximize the contrast of the target tissue and reduce metal artifacts simultaneously. We believe that it would open the door to novel applications for the diagnosis and treatment of several diseases.

Although radiation dose based on X-ray source is becoming a concern, use of micro-computed tomography (m-CT) system continues to grow in diagnostic imaging. To address radiation dose concern in m-CT system, Monte Carlo simulation using Geant4 Application for Tomography Emission (GATE) tool and noise reduction technique have recently developed. Among these techniques, total variation (TV) noise reduction technique is well known to many researchers for X-ray imaging. Also, an important disadvantage of median filter and Wiener filter is low edge preservation compared with recently developed noise reduction methods Thus, the aim of this study was to design TV noise reduction technique based on L1-norm estimation with iterative method and compare to other techniques in m-CT system using GATE simulation. We used 4-dimension (4D) digital mouse whole body (MOBY) phantom and to clarify the feasibility of TV noise reduction technique in m-CT images, we compared the image performance using contrast-to-noise ratio (CNR) and coefficient of variation (COV). According to the results, the average for three image planes (coronal, sagittal and transverse) of CNR and COV of the TV noise reduction technique were 68.07 and 1.61%, respectively. In particular, the CNR and the COV difference between TV noise reduction technique and noisy image were maximum 5.28 and 2.89 times, respectively. In conclusion, the results of this study suggested that TV noise reduction technique can be achieved improved performance and the effect and feasibility of TV noise reduction technique for m-CT imaging can be investigated.

The radiation dose of CT (computed tomography) is generally represented by the CTDI (CT dose index). CTDI, however, does not accurately predict the actual patient doses for different human body sizes because it relies on a cylinder-shaped head (diameter : 16 cm) and body (diameter : 32 cm) phantom. The purpose of this study was to eliminate the drawbacks of the conventional CTDI and to provide more accurate radiation dose information. Projection radiographs were obtained from water cylinder phantoms of various sizes, and the sizes of the water cylinder phantoms were calculated and verified using attenuation profiles. The effective diameter was also calculated using the attenuation of the abdominal projection radiographs of 10 patients. When the results of the attenuation-based method and the geometry-based method shown were compared with the results of the reconstructed-axial-CT-image-based method, the effective diameter of the attenuation-based method was found to be similar to the effective diameter of the reconstructed-axial-CT-image-based method, with a difference of less than 3.8%, but the geometry-based method showed a difference of less than 11.4%. This paper proposes a new method of accurately computing the radiation dose of CT based on the patient sizes. This method computes and provides the exact patient dose before the CT scan, and can therefore be effectively used for imaging and dose control.

In this study, we estimated the characteristics of the optically stimulated luminescence dosimeter (OSLD), and confirmed the evaluation of the OSLD for intensity modulated radiation therapy (IMRT) dose verification. For the estimation of the characteristics of the OSLD, reproducibility, dose linearity, energy dependence, dose-rate dependence, and angular dependence were evaluated. To minimize the effect of the reproducibility on the other studies, we selected 17 OSLDs which had the reproducibility variation margin of ±1.5%. The result showed the linearity of the OSLD from 0.5 to 2 Gy, but from 2 to 6 Gy, supra-linearity was observed. The photon-rays and electron-rays energy dependences of the OSLD were ±1% and ±0.9%, respectively. The dose-rate dependences were ±0.4% for photon-rays, ±0.3% for electrons, and the angular dependence was ±0.7%. To estimate the evaluation of the OSLD for IMRT dose verification, 5 IMRT dose verification cases and 5 RapidArc dose verification cases were selected. The correction factors which were measured in the estimation of the characteristics of the OSLD were used in the dose conversion and the IMRT dose verification standard ±5% were increased to ±7%, because of the relatively high combined uncertainty of the OSLD. In this study, we estimate the characteristics of the OSLD in photon-rays and electron-rays, and confirm the evaluation of the OSLD for IMRT dose assessment through the logic flow chart, which concerned the size of the cancer and partiality of the radiation therapy center.

In order to reduce the amount of noise component in X-ray imaging system, various reduction techniques were frequently used in the field of diagnostic imaging. Although the previous techniques –such as median, Wiener filters and Anscombe noise reduction technique – were able to reduce the noise, the edge information was still damaged. In order to cope with this problem, total variation (TV) noise reduction technique has been developed and researched. The purpose of this study was to evaluate and compare the image quality using normalized noise power spectrum (NNPS) and contrast-to-noise ratio (CNR) through simulations and experiments with respect to the above-mentioned noise reduction techniques. As a result, not only lowest NNPS value but also highest CNR values were acquired using a TV noise reduction technique. In conclusion, the results demonstrated that TV noise reduction technique is proved as the most practical method to ensure accurate denoising in X-ray imaging system.

In single-photon-emission computed tomography (SPECT) with a pixelated semiconductor detector (PSD), not only pinhole collimators but also parallel-hole collimators are often used in preclinical nuclear-medicine imaging systems. The purpose of this study was to evaluate and compare pinhole and parallel-hole collimators in a PSD. For that purpose, we paired a PID 350 (Ajat Oy Ltd., Finland) CdTe PSD with each of the four collimators most frequently used in preclinical nuclear medicine: (1) a pinhole collimator, and (2) low-energy high-resolution (LEHR), (3) low-energy general-purpose (LEGP), and (4) low-energy high-sensitivity (LEHS) parallel-hole collimators. The sensitivity and spatial resolution of each collimator was evaluated using a point source and a hot-rod phantom. The highest sensitivity was achieved using LEHS, followed by LEGP, LEHR, and pinhole. Also, at a source-to-collimator distance of 2 cm, the spatial resolution was 1.63, 2.05, 2.79, and 3.45 mm using pinhole, LEHR, LEGP, and LEHS, respectively. The reconstructed hot-rod phantom images showed that the pinhole collimator and the LEHR parallel-hole collimator give a fine spatial resolution for preclinical SPECT with PSD. In conclusion, we successfully compared different types of collimators for a preclinical pixelated semiconductor SPECT system.

With the advent of the coherent age the implementation of massive digital signal processors (DSP) co-integrated with high speed AD and DA converters became feasible allowing for the realization of huge flexibility of transponders. Today the implementation of variable transponders is mainly based on variable programming of DSP to support different modulation formats and symbol rates. Modulation formats with high flexibility are required such as pragmatic QAM formats and hybrid modulation formats. Furthermore, we report on an implementable probabilistically shaping technique allowing for adjusting the bitrate. We introduce fundamental characteristics of all modes and describe basic operation principles. The modifications of the operational modes are enabled simply by switching between different formats and symbol rates in the DSP to adjust the transponders spectral efficiency, the bitrate and the maximum transmission distance. A fine granularity in bitrate and in maximum transmission distance can be implemented especially by hybrid formats and by probabilistically shaped formats. Furthermore, latter allow for ~+25% increase of the maximum transmission distance due their operation close to the Shannon limit as a consequence of their 2D Gaussian like signal nature. If the flexibility and programmability of transponders is implemented, it can be utilized to support different strategies for the application. The variability in symbol rate is mainly translated into variability in bitrate and in bandwidth consumption. Contrary the variable spectral efficiency translates into a variation of the maximum transmission reach and of the bitrate. A co-adjustment of both options will lead to a superior flexibility of optical transponders to address all requirements from application, transponder and fiber infrastructure perspective.

PURPOSE This work describes the hardware and software developments of a prototype chest digital tomosynthesis (CDT) R/F system. The purpose of this study was to validate the developed system for its possible clinical application on low-dose chest tomosynthesis imaging. METHODS The prototype CDT R/F system was operated by carefully controlling the electromechanical subsystems through a synchronized interface. Once a command signal was delivered by the user, a tomosynthesis sweep started to acquire 81 projection views (PVs) in a limited angular range of ±20°. Among the full projection dataset of 81 images, several sets of 21 (quarter view) and 41 (half view) images with equally spaced angle steps were selected to represent a sparse view condition. GPU-accelerated and total-variation (TV) regularization strategy-based compressed sensing (CS) image reconstruction was implemented. The imaged objects were a flat-field using a copper filter to measure the noise power spectrum (NPS), a Catphan® CTP682 quality assurance (QA) phantom to measure a task-based modulation transfer function (MTFTask ) of three different cylinders' edge, and an anthropomorphic chest phantom with inserted lung nodules. The authors also verified the accelerated computing power over CPU programming by checking the elapsed time required for the CS method. The resultant absorbed and effective doses that were delivered to the chest phantom from two-view digital radiographic projections, helical computed tomography (CT), and the prototype CDT system were compared. RESULTS The prototype CDT system was successfully operated, showing little geometric error with fast rise and fall times of R/F x-ray pulse less than 2 and 10 ms, respectively. The in-plane NPS presented essential symmetric patterns as predicted by the central slice theorem. The NPS images from 21 PVs were provided quite different pattern against 41 and 81 PVs due to aliased noise. The voxel variance values which summed all NPS intensities were inversely proportional to the number of PVs, and the CS method gave much lower voxel variance by the factors of 3.97-6.43 and 2.28-3.36 compared to filtered backprojection (FBP) and 20 iterations of simultaneous algebraic reconstruction technique (SART). The spatial frequencies of the f50 at which the MTFTask reduced to 50% were 1.50, 1.55, and 1.67 cycles/mm for FBP, SART, and CS methods, respectively, in the case of Bone 20% cylinder using 41 views. A variety of ranges of TV reconstruction parameters were implemented during the CS method and we could observe that the NPS and MTFTask preserved best when the regularization and TV smoothing parameters α and τ were in a range of 0.001-0.1. For the chest phantom data, the signal difference to noise ratios (SDNRs) were higher in the proposed CS scheme images than in the FBP and SART, showing the enhanced rate of 1.05-1.43 for half view imaging. The total averaged reconstruction time during 20 iterations of the CS scheme was 124.68 s, which could match-up a clinically feasible time (

For a considerable number of emergency computed tomography (CT) scans, patients are unable to position their arms above their head due to traumatic injuries. The arms-down position has been shown to reduce image quality with beam-hardening artifacts in the dorsal regions of the liver, spleen, and kidneys, rendering these images non-diagnostic. The purpose of this study was to evaluate the effect of arm position on the image quality in patients undergoing whole-body CT. We acquired CT scans with various acquisition parameters at voltages of 80, 120, and 140 kVp and an increasing tube current from 200 to 400 mAs in 50 mAs increments. The image noise and the contrast assessment were considered for quantitative analyses of the CT images. The image noise (IN), the contrast-to-noise ratio (CNR), the signal-to-noise ratio (SNR), and the coefficient of variation (COV) were evaluated. Quantitative analyses of the experiments were performed with CT scans representative of five different arm positions. Results of the CT scans acquired at 120 kVp and 250 mAs showed high image quality in patients with both arms raised above the head (SNR: 12.4, CNR: 10.9, and COV: 8.1) and both arms flexed at the elbows on the chest (SNR: 11.5, CNR: 10.2, and COV: 8.8) while the image quality significantly decreased with both arms in the down position (SNR: 9.1, CNR: 7.6, and COV: 11). Both arms raised, one arm raised, and both arms flexed improved the image quality compared to arms in the down position by reducing beam-hardening and streak artifacts caused by the arms being at the side of body. This study provides optimal methods for achieving higher image quality and lower noise in abdominal CT for trauma patients.

The single photon emission computed tomography (SPECT) based on pixelated Cadmium Telluride (CdTe) detector has been promising for high resolution small animal imaging. For the feasibility of our ultra-high resolution SPECT system with CdTe, we compared the quality of the reconstructed image of our SPECT system to that of a conventional small animal SPECT system with NaI(Tl) detector. The pixel size of CdTe detector was 0.35 mm × 0.35 mm which was available for a real detector (PID350, AJAT, Finland). The detector size was 44.8 × 44.8 mm with 128 × 128 pixels and the thickness of this detector was 1 mm. The intrinsic resolution of CdTe detector and that of NaI(Tl) detector were 0.35 mm and 2.3 mm, respectively. The height parallel hole collimator made of lead was 25 mm and that of a septum was 0.2 mm. The shape of that parallel hole collimator and its radius were hexagonal and 0.5 mm, respectively. A SPECT liver scan was simulated for both SPECT with CdTe and conventional SPECT system using voxelized MOBY phantom. All SPECT images were obtained using 120 projection views acquired from 0° to 360° with a 3°. Slices were reconstructed using an Ordered Subsets Expectation Maximization (OS-EM) and 5 iterations with 4 subsets. We compared the quality of images for two systems in terms of spatial resolution (FWHM), sensitivity, signal-to-noise ratio (SNR), and contrast-to-noise (CNR). Our simulation results indicated that the reconstructed SPECT images obtained with CdTe detector showed higher resolution compared to those with the conventional scintillation detector. These results demonstrated that the SPECT imaging based on pixelated CdTe detector can improve the performance of SPECT system for small animal imaging.

Purpose: A pretherapy 124I-metaiodobenzylguanidine (MIBG) positron emission tomography (PET)∕computed tomography (CT) provides a potential method to estimate radiation dose to normal organs, as well as tumors prior to 131I-MIBG treatment of neuroblastoma or pheochromocytoma. The aim of this work was to estimate human-equivalent internal radiation dose of 124I-MIBG using PET∕CT data in a murine xenograft model. Methods: Athymic mice subcutaneously implanted with NB1691 cells that express high levels of human norepinephrine transporter (n=4) were imaged using small animal microPET∕CT over 96 h (approximate imaging time points: 0.5, 2, 24, 52, and 96 h) after intravenous administration of 3.07–4.84 MBq of 124I-MIBG via tail vein. The tumors did not accumulate 124I-MIBG to a detectable level. All four animals were considered as control and organ radiation dosimetry was performed. Volumes of interest were drawn on the coregistered CT images for thyroid, heart, lung, liver, kidney, and bladder, and transferred to PET images to obtain pharmacokinetic data. Based on tabulated organ mass distributions for both mice and adult male human, preclinical pharmacokinetic data were extrapolated to their human-equivalent values. Radiation dose estimations for different age groups were performed using the OLINDA|EXM software with modified tissue weighting factors in the recent International Commission on Radiological Protection (ICRP) Publication 103. Results: The mean effective dose from 124I-MIBG using weighting factors from ICRP 103 to the adult male was estimated at 0.25 mSv∕MBq. In different age groups, effective doses using values from ICRP 103 were estimated as follows: Adult female: 0.34, 15-yr-old: 0.39 mSv∕MBq, 10-yr-old: 0.58 mSv∕MBq, 5-yr-old: 1.03 mSv∕MBq, 1-yr-old: 1.92 mSv∕MBq, and newborn: 3.75 mSv∕MBq. For comparison, the reported effective dose equivalent of 124I-NaI for adult male (25% thyroid uptake, MIRD Dose Estimate Report No. 5) was 6.5 mSv∕MBq. Conclusions: The authors estimated human-equivalent internal radiation dose of 124I-MIBG using preclinical imaging data. As a reference, the effective dose estimation showed that 124I-MIBG would deliver less radiation dose than 124I-NaI, a radiotracer already being used in patients with thyroid cancer.

The number of CT (computed tomography) examinations in the diagnosis field has increased, and X-ray exposure to patients has also continued to increase. As the number of CT examinations is increasing in the general population, the number of pediatric CT examinations is rapidly increasing as well. The radiation dose from CT for pediatric patients remains a major concern because the risk related to ionizing radiations is higher in children than in adults. The purpose of this study was to evaluate radiation dose, image noise, and image contrast as a function of tube voltage (kVp) and tube current (mAs) in dierent phantoms, which were intended to simulate abdominal size, and to provide guidance on dose reduction on the basis of patient dimensions, as well as technical parameters. In this study, MDCT (multi-detector computed tomography) was used as an X-ray generator, and PMMA (polymethylmethacrylate) phantoms were used in all experiments. PMMA phantom diameters were 10 cm, 16 cm, and 32 cm corresponding to newborn, age 5, and adult abdominal sizes, respectively. To evaluate radiation dose, the CTDIw (weighted CT dose index) was calculated from the CTDI measured using ion chamber, and to evaluate image quality, image noise and image contrast were measured from a scanned image. Finally, the CNRD (dose-weighted contrast-to-noise ratio) was calculated from the radiation dose, image noise, and image contrast to optimize the technical factors. The radiation dose increased as a function of kVp and mAs and decreased as a function of the phantom diameter. Especially, for increasing tube voltage from 80 to 140 kVp, there were 395.08% and 448.27% increases in radiation dose for 10 cm and 32 cm PMMA phantoms, respectively. The image noise decreased as a function of kVp and mAs and increased as a function of the phantom diameter. And, the image contrast decreased as a function of kVp and phantom diameter and remained fixed as a function of mAs. The values of the CNRD were maximum at 80 kVp for all three phantoms. The results of this study show that it is possible to reduce radiation dose and maintain image quality through the use of lower technical factors (kVp and mAs) for small-sized phantom corresponding to pediatric patients and to provide guidance on radiation dose reduction on the basis of the patient’s dimensions.

The aim of this study was to increase the labeling efficiency of 99m Tc-RBC. We compared the clinical utility of the conventional modified in-vitro method (MIM) with our new AMC method. Seventy-two patients (M:44 F:28) were examined. The MIM and AMC method were carried out at the same time. The mean labeling efficiency (%) of MIM vs. AMC were as follows: (1) 90.8 ± 11.4 vs. 95.9 ± 6.8 in total ( p = 0.0001); (2) 89.7 ± 12.0 vs. 95.7 ± 6.8 in males ( p = 0.0001), 92.9 ± 10.6 vs. 96.3 ± 3.9 in females ( p = 0.0001); (3) 89.5 ± 12.9 vs. 95.5 ± 7.8 in the G-I bleeding scan ( p = 0.0001), 94.6 ± 4.8 vs. 96.7 ± 3.5 in the liver hemangioma scan ( p = 0.035), 96.2 ± 1.96 vs. 97.5 ± 1.11 in the MUGA scan ( p = 0.08); and (4) 89.4 ± 12.5 vs. 95.5 ± 7.6 in the decreased RBC count group ( p = 0.0001), and 95.9 ± 3.9 vs. 97.1 ± 3.1 the normal RBC count group ( p = 0.062). There were significant differences in labeling efficiency between the MIM and AMC methods. In particular, the AMC labeling method was quite useful in decreased RBC count patients.

Computed radiography (CR) images will require large storage facilities and long transmission times for picture archiving and communications system (PACS) implementation. The American College of Radiology and National Equipment Manufacturers Association (ACR/NEMA) group is planning to adopt a JPEG2000 compression algorithm in the Digital Imaging and Communications in Medicine (DICOM) standard for better utilization of medical images. The purpose of this study was to evaluate and compare the results of JPEG and JPEG2000 compressions in medical images. We applied various compression ratios of JPEG and JPEG2000 to chest, abdomen, and hand images obtained using the AGFA CR (Computed Radiography) system (AGFAMD-4.0, BELGIUM) and the FUJI CR system (FCR 9000C, JAPAN). A quantitative evaluation was carried out using the PSNR (peak signal to noise ratio), which is a commonly used measure for the evaluation of reconstructed images and measures how the reconstructed images differ from the original images. In the JPEG and JPEG2000 comparison for compression ratios up to 60:1, the PSNR value showed less than 30 dB in accordance with CR modalities and image regions in JPEG compression whereas JPEG2000 showed more than 30 dB in the same compression ratios for both AGFA and FUJI CR images. As the compression ratios were increased to 200:1, use of the JPEG2000 algorithm showed over 30 dB of the PSNR value in accordance with CR modalities and image regions. In general, when the PSNR value gets greater than or equal to 30 dB, the quality of the processed image is acceptable. Nevertheless, the PSNR value cannot absolutely stand for the quality in terms of perceptibility. The artifact of blockiness is found to be visible not only for the AGFA CR image at 40:1 but also for the FUJI CR image at 40:1 and 60:1 in JPEG compression while no significant artifact were observed in the JPEG2000 compressed image up to 200:1. In conclusion, JPEG2000 appeared to be a more effective method of compression than JPEG in medical imaging applications based on the PSNR value, ROC studies may be needed to establish whether these applications are suitable for real clinical situations requiring diagnostic accuracy.

Digital radiography has gained popularity in many areas of clinical practice. This transition brings interest in advancing the methodologies for image quality characterization. However, as the methodologies for such characterizations have not been standardized, the results of these studies cannot be directly compared. The primary objective of this study was to standardize methodologies for image quality characterization. The secondary objective was to evaluate affected factors to Modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) according to image processing algorithm. Image performance parameters such as MTF, NPS, and DQE were evaluated using the international electro-technical commission (IEC 62220-1)-defined RQA5 radiographic techniques. Computed radiography (CR) images of hand posterior-anterior (PA) for measuring signal to noise ratio (SNR), slit image for measuring MTF, white image for measuring NPS were obtained and various Multi-Scale Image Contrast Amplification (MUSICA) parameters were applied to each of acquired images. In results, all of modified images were considerably influence on evaluating SNR, MTF, NPS, and DQE. Modified images by the post-processing had higher DQE than the MUSICA=0 image. This suggests that MUSICA values, as a post-processing, have an affect on the image when it is evaluating for image quality. In conclusion, the control parameters of image processing could be accounted for evaluating characterization of image quality in same way. The results of this study could be guided as a baseline to evaluate imaging systems and their imaging characteristics by measuring MTF, NPS, and DQE.

Single photon emission computed tomography (SPECT) using a pixelated Cadmium Telluride (CdTe) detector is a promising technology for high-resolution, small animal imaging. This study demonstrates the feasibility of using our high resolution SPECT system with CdTe in quantitative study in mouse brain. The CdTe detector had 0.35 mm x 0.35 mm2 pixels, which is similar to the size of the available detector (PID350, AJAT, Finland). The CdTe detector was 44.8 mm x 44.8 mm2 with 128 x 128 pixels and was 1 mm thick. The intrinsic resolutions of CdTe and was 0.35 mm. The parallel hole collimator of lead was 25 mm high, and the septum was 0.2 mm high. The parallel hole collimator was hexagonal with a 0.5 mm radius. A voxelized MOBY phantom was used to model the mouse brain for the quantitative dopamine transporters (DAT) binding study. A SPECT brain scan of the MOBY phantom was simulated using our system with CdTe. All SPECT images were obtained using 120 projection views acquired from 0° to 360° with a 3° step. Slices were reconstructed using an Ordered Subsets Expectation Maximization (OS-EM) with 8 iterations and 4 subsets. We investigated the quality of the images from our system in terms of spatial resolution (FWHM), sensitivity, signal-to-noise ratio (SNR), and contrastto-noise ratio (CNR). The spatial resolution of our new SPECT with a CdTe detector was about 2.32 mm at 3 cm. The sensitivity at 3 cm was 23.22 counts/sec/MBq. The SNR and CNR of the image from the CdTe detector were 0.8 and 0.74, respectively. These results demonstrate that SPECT imaging using a pixelated CdTe detector is applicable in quantitative study of neurorecptor binding sites in the mouse brain.

As small animal studies using radiation exposure increase, it becomes more important to estimate accurate dose for the animals in order to explain and control the potential radiation toxicity or treatment efficacy. The purpose of this study was to determine the radiation dose in a realistic mouse brain tissue for dosimetric estimates using geant4 application for tomographic emission simulations (GATE), and to extend its techniques to various small animal CT applications. The realistic mouse phantom (MOBY phantom) is based on high resolution 3D magnetic resonance microscopy data, and the geometry was developed using a segmented C57BL/6 mouse that weighed 33 g. Recently, 37 segmented tissues have been added to voxel-based MOBY brain developed by Johns Hopkins University. A small animal CT system (micro-CT) with Gd2O2S scintillator was performed using 50 kVp, 0.15 mAs (0.5 second), 360° of rotation, and 400 projections. For validating simulation studies with respect to physical measurements for micro-CT, the measured and simulated airkerma values were compared, and the measured and simulated values measured in the validation CT ion chamber study were 3.32 and 3.69 μC/kg air, respectively. The total absorbed dose over all measurements to the brain (37 tissues) is 60.2 mGy. Among tissues of brain, the absorbed dose of cerebral_cortex (20.55 mGy) was highest while the one of pineal_gland (0.02 mGy) was lowest. This result can be used in control of brain tissue doses and preclinical targeted radiotherapy experiments as dosimetric database. In addition, in order to calculate accurate absorbed dose of brain tissues, accurate modeling is needed for X-ray spectrum, detector alignment, and uncertainty in elemental composition of simulated materials.

Small-animal computed tomography (micro-CT) imaging devices are increasingly being used in biological research. While investigators are mainly interested in high-contrast, low-noise, and high-resolution anatomical images, relatively large radiation doses are required, and there is also growing concern over the radiological risk from preclinical experiments. This study was conducted to determine the radiation dose in a mouse model for dosimetric estimates using the GEANT4 application for tomographic emission simulations (GATE) and to extend its techniques to various small-animal CT applications. Radiation dose simulations were performed with the same parameters as those for the measured micro-CT data, using the MOBY phantom, a pencil ion chamber and an electrometer with a CT detector. For physical validation of radiation dose, absorbed dose of brain and liver in mouse were evaluated to compare simulated results with physically measured data using thermoluminescent dosimeters (TLDs). The mean difference between simulated and measured data was less than 2.9% at 50 kVp X-ray source. The absorbed doses of 37 brain tissues and major organs of the mouse were evaluated according to kVp changes. The absorbed dose over all of the measurements in the brain (37 types of tissues) consistently increased and ranged from 42.4 to 104.0 mGy. Among the brain tissues, the absorbed dose of the hypothalamus (157.8–414.30 mGy) was the highest for the beams at 50–80 kVp, and that of the corpus callosum (11.2–26.6 mGy) was the lowest. These results can be used as a dosimetric database to control mouse doses and preclinical targeted radiotherapy experiments. In addition, to accurately calculate the mouse-absorbed dose, the X-ray spectrum, detector alignment, and uncertainty in the elemental composition of the simulated materials must be accurately modeled.

[(124)I]m-iodobenzylguanidine ((124)I-mIBG) provides a quantitative tool for pretherapy tumor imaging and dosimetry when performed before [(131)I]m-iodobenzylguanidine ((131)I-mIBG) targeted radionuclide therapy of neuroblastoma. (124)I (T (1/2) = 4.2 days) has a comparable half-life to that of (131)I (T (1/2) = 8.02 days) and can be imaged by positron emission tomography (PET) for accurate quantification of the radiotracer distribution. We estimated expected radiation dose in tumors from (131)I-mIBG therapy using (124)I-mIBG microPET/CT imaging data in a murine xenograft model of neuroblastoma transduced to express high levels of the human norepinephrine transporter (hNET).In order to enhance mIBG uptake for in vivo imaging and therapy, NB 1691-luciferase (NB1691) human neuroblastoma cells were engineered to express high levels of hNET protein by lentiviral transduction (NB1691-hNET). Both NB1691 and NB1691-hNET cells were implanted subcutaneously and into renal capsules in athymic mice. (124)I-mIBG (4.2-6.5 MBq) was administered intravenously for microPET/CT imaging at 5 time points over 95 h (0.5, 3-5, 24, 48, and 93-95 h median time points). In vivo biodistribution data in normal organs, tumors, and whole-body were collected from reconstructed PET images corrected for photon attenuation using the CT-based attenuation map. Organ and tumor dosimetry were determined for (124)I-mIBG. Dose estimates for (131)I-mIBG were made, assuming the same in vivo biodistribution as (124)I-mIBG.All NB1691-hNET tumors had significant uptake and retention of (124)I-mIBG, whereas unmodified NB1691 tumors did not demonstrate quantifiable mIBG uptake in vivo, despite in vitro uptake. (124)I-mIBG with microPET/CT provided an accurate three-dimensional tool for estimating the radiation dose that would be delivered with (131)I-mIBG therapy. For example, in our model system, we estimated that the administration of (131)I-mIBG in the range of 52.8-206 MBq would deliver 20 Gy to tumors.The overexpression of hNET was found to be critical for (124)I-mIBG uptake and retention in vivo. The quantitative (124)I-mIBG PET/CT is a promising new tool to predict tumor radiation doses with (131)I-mIBG therapy of neuroblastoma. This methodology may be applied to tumor dosimetry of (131)I-mIBG therapy in human subjects using (124)I-mIBG pretherapy PET/CT data.

The dual-energy computed tomography (CT) techniques can be adopted to separate the materials having similar Houndsfield Unit (HU) value such as tissues. In the technique, CT image values can be described as effective atomic number and electron density using the dual-energy equation. In this work, we measured effective atomic number and electron density using dual-energy CT images and assessed the image quality in vascular application. For the effective atomic number assessment, the measurements of a Polymethyl methacrylate (PMMA) and water demonstrated small discrepancies of 3.28 % and 5.56 %, respectively. For electron density measurement, the experimental errors of PMMA and water were 7.83 % and 4.00 %, respectively. The trend obtained when comparing the HU values and absolute values such as effective atomic number and electron density demonstrates that the CNR of the HU values is higher than that of the absolute values such as effective atomic number and electron density. With contrast media having low concentration, it is remarkable that the effective atomic number image occasionally has higher CNR values than the HU images. In this study, small discrepancies between the experimental values and known values were obtained. The CNR values provided meaningful results for the absolute measurements in a dual-energy CT technique.

The cone-beam computed tomography (CBCT) is a useful modality in diagnostic imaging due to the properties of fast volume coverage, lower radiation dose, easy hardware implementation, and higher spatial resolution. Recently, attention is being paid to address the noise and resolution relationship for CBCT. In CBCT system, image noise and spatial resolution play important roles in image quality. However, there has not been done many works for evaluating the relationship of image noise and the spatial resolution in CBCT. In this study, we evaluated the image noise and spatial resolution as a function of filter, number of projections, and voxel size on reconstructed images in CBCT. The simulated projection data of Catphan 600 phantom were reconstructed using the FDK algorithm. To evaluate the image noise and spatial resolution, the coefficient of variation (COV) of attenuation coefficient and the modulation transfer function (MTF) in axial images were calculated, respectively. The filters used for reconstruction were Ram-lak, Shepp-logan, Cosine, Hamming, and Hann. A number of projections were 161, 321, 481 and 642 acquired from scanning of 360 degree and the voxels with sizes of 0.10 mm, 0.15 mm, 0.20 mm, 0.25 mm and 0.30 mm were used. The image noise given by Hann filter was the lowest and decreased as functions of number of projections and voxel size. The spatial resolution given by Ram-lak filter was the highest and increased as a function of number of projections, decreased as a function of voxel size. The results of this study show the relationship of image noise and spatial resolution in CBCT and the characteristics of reconstruction factors for trade-off between the image noise and spatial resolution. It can also provide information of image noise and spatial resolution for adaptive image.

A photon counting detector based on semiconductor materials is a very promising approach for x-ray imaging. Cadmium zinc telluride (CZT) semiconductor has a high atomic number which results in higher absorption coefficients for x-rays. However, the CZT detectors exhibit several problems with hole trapping and charge sharing. Charge sharing occurs due to diffusion of charge and characteristic x-ray escape and scattered x-rays in the detectors. In this study, we evaluated the effect of interaction with CZT detector using Monte Carlo simulations. To demonstrate the effectiveness of CZT detector in clinical application, we reported confirmation of CNR improvement in K-edge images, and material decomposition using energy selective windows. X-ray energy spectrum acquired at 120 kVp tube voltage and 2 mm Al filtration and 10 cm added water phantom in the x-ray beam. Geant4 Application for Tomographic Emission (GATE) version 6.0 was used for a CZT crystal with size of 10x10 mm2 and thickness of 4 mm. The detector pixel with sizes of 0.09x0.09, 0.45x0.45, and 0.90x0.90 mm2 were simulated. For all pixel sizes, the x-ray spectra of the simulations were distorted towards the lower energy region. Because the characteristic x-rays add counts in the range of 20-40 keV. The magnitude of this deterioration is substantial for small pixel sizes. However, we demonstrated that the distortion of spectrum does not greatly affect the x-ray imaging. The GATE simulation model and these results may be used as a basis of development of energy-resolved photon counting x-ray detector. We believe that the CZT detector may enhance the detectability of multi-energy x-ray imaging.

Our aim in this study was to examine the resolution effects of breast thickness in magnification technique by evaluating generalized modulation transfer function (GMTF) including the effect of focal spot, effective pixel size and the scatter. The PMMAs ranging from 10 to 40 mm in thickness were placed on a standard supporting platform that was positioned to achieve magnification factors ranging from 1.2 to 2.0. As the magnification increased, the focal spot MTF degraded while the detector MTF improved. A small focal spot resulted in an improvement of GMTF due to a smaller effective pixel size by magnification. In contrast, a large focal spot resulted in significant degradation of GMTF due to dominating the effect of focal spot blurring. The resolution of small focal spot did improve slightly with increasing PMMA thickness for magnification factors less than 1.8. System resolution decreased with increasing PMMA thickness for magnification factors greater than 1.8, since focal spot blur begins to dominate spatial resolution. In particular, breast thickness had a large effect on the resolution at lower frequencies as a low frequency drop effect. Hence, the effect of compressed breast thickness should be considered for the standard magnification factor of 1.8 that is most commonly used in clinical practice. Our results should provide insights for determining optimum magnification in clinical application of digital mammography, and our approaches can be extended to a wide diversity of radiological imaging systems.

A pretherapy 124I-metaiodobenzylguanidine (MIBG) positron emission tomography (PET)/computed tomography (CT) provides a potential method to estimate radiation dose to normal organs, as well as tumors prior to 131I-MIBG treatment of neuroblastoma or pheochromocytoma. The aim of this work was to estimate human-equivalent internal radiation dose of 124I-MIBG using PET/CT data in a murine xenograft model.Athymic mice subcutaneously implanted with NB1691 cells that express high levels of human norepinephrine transporter (n = 4) were imaged using small animal microPET/CT over 96 h (approximate imaging time points: 0.5, 2, 24, 52, and 96 h) after intravenous administration of 3.07-4.84 MBq of 124I-MIBG via tail vein. The tumors did not accumulate 124I-MIBG to a detectable level. All four animals were considered as control and organ radiation dosimetry was performed. Volumes of interest were drawn on the coregistered CT images for thyroid, heart, lung, liver, kidney, and bladder, and transferred to PET images to obtain pharmacokinetic data. Based on tabulated organ mass distributions for both mice and adult male human, preclinical pharmacokinetic data were extrapolated to their human-equivalent values. Radiation dose estimations for different age groups were performed using the OLINDA/EXM software with modified tissue weighting factors in the recent International Commission on Radiological Protection (ICRP) Publication 103.The mean effective dose from 124I-MIBG using weighting factors from ICRP 103 to the adult male was estimated at 0.25 mSv/MBq. In different age groups, effective doses using values from ICRP 103 were estimated as follows: Adult female: 0.34, 15-yr-old: 0.39 mSv/MBq, 10-yr-old: 0.58 mSv/MBq, 5-yr-old: 1.03 mSv/MBq, 1-yr-old: 1.92 mSv/MBq, and newborn: 3.75 mSv/ MBq. For comparison, the reported effective dose equivalent of 124I-NaI for adult male (25% thyroid uptake, MIRD Dose Estimate Report No. 5) was 6.5 mSv/MBq.The authors estimated human-equivalent internal radiation dose of 124I-MIBG using preclinical imaging data. As a reference, the effective dose estimation showed that 124I-MIBG would deliver less radiation dose than 124I-NaI, a radiotracer already being used in patients with thyroid cancer.

The photon counting detectors such as cadmium zinc telluride (CZT) and cadmium telluride (CdTe) have powerful advantages compared to energy integrating detectors. CZT or CdTe can detect individual gamma-ray or x-ray photon with energy discrimination. In recent years, energy-resolving and material decomposition x-ray imaging based on photon counting detectors has attracted attention from biomedical imaging researchers. We evaluated a large-area (20 cm × 20 cm) CZT detector originally built as a radionuclide detector for a small animal SPECT/CT system in combination of a microfocus x-ray source with a general goal of developing a material-decomposition imaging method. In this paper, we present experimental results from a feasibility study of multi-material decomposition imaging using the developed small animal SPECT/CT system. Our small animal SPECT/CT system has the unique capability to arrange detectors and sources flexibly. For the multi-material decomposition scan, the CZT detector and the x-ray tube were re-arranged in line. List-mode data of a phantom containing 7 different materials, with a range of densities and atomic numbers, illuminated by x-ray were acquired. The x-ray exposure conditions were: 50 kVp and 0.5 mA with 1.5-mm Al filtration. The acquired image was corrected for bad and hot pixels, gain, and offset. The attenuation profiles of each material were calculated against the x-ray energy. Measured attenuation profiles of each material were in a good agreement with the reference data of the NIST physics laboratory. In this study, we demonstrated that multi-material decomposition imaging is experimentally feasible using the photon-counting CZT detector and polychromatic x-ray. Since our system allows rotation and a large active area of CZT, we will acquire material-decomposition data tomographically in the near future.

The purpose of this study was to demonstrate CTDI estimation using GATE simulations, and to extend its techniques to various CT applications. We simulated various phantom sizes to estimate CTDI100 values for different patients. The simulations were performed using a single axial scan using standard PMMA (polymethylmethacrylate) head and body phantoms. Simulations of exposure in air were performed to compare simulated results with physically measured data. Simulations of absorbed dose in PMMA digital phantoms were performed to compare simulated results with physically measured data in corresponding PMMA physical phantoms at 5 different positions (at center, and 12hr, 3hr, 6hr, 9hr positions in phantoms). Additional simulations were performed for PMMA digital phantoms of various diameters (1-50 cm) at various kVp (80, 100, 120, 140 kVp) and mAs (100, 200, 300, 400 mAs) levels. For the PMMA head and body phantoms, the results of simulations showed an agreement with measured data by a maximum percent difference of 8.3% (head), 4.2% (body) for all energies applied. For the different positions, the results of simulations showed an agreement with measured data by a maximum per position difference of 4.7% (head), 5.1% (body) for 120 kVp. Within these limitations, for both various kVp and mAs levels, the results showed that CTDI100 values nonlinearly decreased as a function of diameter. For various diameters, the results showed that the CTDI100 values nonlinearly and linearly increased as a function of kVp and mAs, respectively.

Current digital radiographic systems are rapidly growing in clinical applications. The purpose of this study was to evaluate the diagnostic performance of storage phosphor radiography and digital selenium radiography (DSR) at different tube voltages in the detection of simulated chest lesions. Patterns of simulated interstitial lung disease, incipient infiltration, and nodules were superimposed over an anthropomorphic chest phantom. A simulated chest phantom radiograph was obtained with storage phosphor radiography and DSR at different tube voltages (70 kV, 90 kV, and 120 kV). A total of 18,000 observations were analyzed using a receiver operating characteristic (ROC) analysis. The detection of all lesions showed higher Az values at 70 kV than 120 kV with storage phosphor radiography. For the DSR, mean Az values at 70 kV were higher than other tube voltages not all lesions but for micro-nodule interstitial lung disease, linear interstitial lung disease, and incipient infiltration. However, these results were not significantly different (P ≫ .05). Based on these results, a clinical study should be performed to judge the use of suitable kV according to the type of detector system and lesions.

Digital radiography has gained popularity in many areas of clinical practice. With this transition has come interest in advancing methodologies for image quality characterization. Modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) are widely accepted measurements of system performance. The NPS is one of the most common metrics describing the noise amplitude and texture observed in images obtained with a uniform field of radiation. Yet the comparability of the results is compromised by the different measurement parameters and evaluation methods. Because of the variety of methods used, it is difficult to compare previously published NPS results using different methodologies. In this paper, the following factors were evaluated for their effect on the measured NPS using the international electro-technical commission (IEC 62220-1)-defined RQA5 (additional Filter 21 mmAl, 72 kVp) radiographic techniques: impact of different exposure levels or radiation qualities, impact of the region of interest (ROI) and sub-ROI size, directional dependence, impact of overlapping versus non-overlapping sub-ROI size, and positional dependence for establishing the ROI. The results of Agfa CR (computed radiography, Toshiba, E8239X generator with Agfa CR 25 Corp.) showed that the shape of the normalized noise power spectrum (NNPS) curves decreased gradually as spatial frequency was increased. The various processing factors used in this study were found to have relatively little influence on the measured NPS. Our results suggest that the various processing factors could be used for computing the NPS with confidence. The results of this study could be used as a baseline to standardize the NPS processing by measuring NPS for different methodologies.

Number of radiologic exams using digital imaging systems has rapidly increased with advanced imaging technologies. However, it has not been paid attention to the radiation dose in clinical situations. It was the motivation to study radiation dosimetry in the DR system. The objective of this study was to measure beam quality and patient's dose using DR system and to compare them to both IEC standard and IAEA guidelines. The measured average dose for chest and abdomen was 1.376 mGy and 9.501 mGy, respectively, compared to 0.4 mGy and 10.0 mGy in IAEA guidelines. The results also indicated that the DR system has a lower radiation beam quality than that of the IEC standard. The results showed that the patients may be exposed higher radiation for chest exams and lower radiation for abdomen exams using DR system. IAEA Guidelines were prepared based on western people which may be different weight and height for patients compared them to Korean. In conclusion, a new guideline for acceptable DR dosimetry for Korean patients may need to be developed with further studies for large populations. We believe that this research greatly help to introduce the importance of the dosimetry in diagnostic radiology in Korea. And, a development of database for dosimetry in diagnostic radiology will become an opportunity of making aware of radiation safety of medical examination to patient.

The wireless mobile service with a high bit rate using CDMA-1X EVDO is now widely used in Korea. Mobile devices are also increasingly being used as the conventional communication mechanism. In this study, we have developed the emergency worklist system, JPEG 2000 compression module, and emergency medical information integration viewer, mobile web PACS. We have also developed a web-based mobile system that communicates patient information and images, using CDMA-1X EVDO for emergency diagnosis. It is composed of a mobile web application system using the Microsoft Windows 2003 server and an internet information service. A mobile web PACS used for a database managing patient information and images was developed by using Microsoft access 2003. A wireless mobile emergency patient information and imaging communication system is developed by using Microsoft Visual Studio. NET, and JPEG 2000 ActiveX control for PDA phone was developed by using the Microsoft Embedded Visual C++. Also, the CDMA-1X EVDO is used for connections between mobile web server and the PDA phone, and between ambulance car and hospital. This system allows fast access to the patient information database, storing both medical images and patient information anytime and anywhere. In particular, images were compressed into a JPEG2000 format and transmitted from a mobile web PACS within the hospital to the radiologist using a PDA phone located outside of the hospital. Also, this system shows radiological images as well as physiological signal data, including blood pressure, vital signs, and etc, in the web browser of the PDA phone so that radiologists can diagnose more effectively. We successfully demonstrated this system using an RW-6100 PDA phone used in the Yonsei university medical center in Korea.

The number of hospitals installing the PACS (Picture Archiving and Communications System) had been rapidly increased. In case of patients who are referred to other hospitals, their image information which is set of DICOM (Digital Imaging and Communications in Medicine) studies related with radiology images is transferred to the referred hospital. The DICOM studies are exported and distributed on the portable storage media such as a CD (Compact Disk). However, when Hospital’ PACS staffs are trying to import the DICOM CD files to a server, some images could not be imported from the portable storage media. Even if they were successfully imported, some of them were not able to display. To resolve these issues, each representative of the hospitals and vendors started joint projects to define and validate the DICOM CD data sets to improve the compatibility between the DICOM CD data and PACS solution. This study reports the procedure which is to make “the DICOM CD recommended a guidelines document” and the results that we validated the DICOM data sets by “the DICOM CD validation toolkit” which is developing in at present.

Current digital radiography systems are rapidly growing in clinical applications. The purpose of this study was to evaluate the characteristics of a mobile digital radiographic system. The performance of the mobile DR system was evaluated by measuring the modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). Measurements were made on a LISTEM Mobix-1000 generator and a Teleoptic PRA Alpha- R4000 detector. Imaging characteristics were measured for these two systems using the IEC 61267's RQA5 (kVp: 74, additional filtration: 21 mmAl) radiographic condition. The result for the mobile DR system, MTF at 10% and DQE values using 0.19mR at 0 cycles/mm were measured as 2.4 cycles/mm and 43%, respectively. This high DQE at low frequencies may be useful for low frequency information. The NPS curves gradually decreased at high spatial frequencies. The NPS and the DQE curves show some exposure dependency with lower NPS and DQE value at higher exposure. The results suggested that mobile DR system could be integrated with emergency ambulance system in teleradiologic imaging applications.

Multi-detector computed tomography (MDCT) can be used to easily and rapidly perform numerous acquisitions, possibly leading to a marked increase in the radiation dose to individual patients. Technical options dedicated to automatically adjusting the acquisition parameters according to the patient's size are of specific interest in pediatric radiology. A constant tube potential reduction can be achieved for adults and children, while maintaining a constant detector energy fluence. To evaluate radiation dose, the weighted CT dose index (CTDIw) was calculated based on the CT dose index (CTDI) measured using an ion chamber, and image noise and image contrast were measured from a scanned image to evaluate image quality. The dose-weighted contrast-to-noise ratio (CNRD) was calculated from the radiation dose, image noise, and image contrast measured from a scanned image. The noise derivative (ND) is a quality index for dose efficiency. X-ray spectra with tube voltages ranging from 80 to 140 kVp were used to compute the average photon energy. Image contrast and the corresponding contrast-to-noise ratio (CNR) were determined for lesions of soft tissue, muscle, bone, and iodine relative to a uniform water background, as the iodine contrast increases at lower energy (i.e., k-edge of iodine is 33 keV closer to the beam energy) using mixed water-iodine contrast normalization (water 0, iodine 25, 100, 200, and 1000 HU, respectively). The proposed values correspond to high quality images and can be reduced if only high-contrast organs are assessed. The potential benefit of lowering the tube voltage is an improved CNRD, resulting in a lower radiation dose and optimization of image quality. Adjusting the tube potential in abdominal CT would be useful in current pediatric radiography, where the choice of X-ray techniques generally takes into account the size of the patient as well as the need to balance the conflicting requirements of diagnostic image quality and radiation dose optimization.