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In this work, we propose and analyze a new concept of gamma ray imaging that corresponds to a gamma camera with a mobile collimator, which can be used in vivo, during surgical interventions for oncological patients for localizing regions of interest such as tumors or ganglia. The benefits are a much higher sensitivity, better image quality and, consequently, a dose reduction for the patient and medical staff. This novel approach is a practical solution to the overlapping problem which is inherent to multi-pinhole gamma camera imaging and single photon emission computed tomography and which translates into artifacts and/or image truncation in the final reconstructed image. The key concept consists in introducing a relative motion between the collimator and the detector. Moreover, this design could also be incorporated into most commercially available gamma camera devices, without any excessive additional requirements. We use Monte Carlo simulations to assess the feasibility of such a device, analyze three possible designs and compare their sensitivity, resolution and uniformity. We propose a final design of a gamma camera with a high sensitivity ranging from 0.001 to 0.006 cps/Bq, and a high resolution of 0.5–1.0 cm (FWHM), for source-to-detector distances of 4–10 cm. Additionally, this planar gamma camera provides information about the depth of source (with approximate resolution of 1.5 cm) and excellent image uniformity.

Aliasing artefact is an imaging distortion phenomenon experienced in a wide variety of medical imaging modalities. This case report illustrates its occurrence during planar gamma camera nuclear medicine imaging under non-clinical conditions using experimental incorrect selection of collimators. In accordance with provision of an optimal service, nuclear medicine practitioners are recommended to have sufficient technical expertise along with knowledge of gamma camera operation. The purpose, construction and interaction of collimators used during planar imaging are presented herein with specific regards to the aliasing phenomenon. Furthermore, this case report recommends the careful planning of worklists to avoid frequent collimator changes to reduce the risk of human error. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Medical Equipment Journal is the property of Chinese Medical Equipment Journal Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Although the technological advances in hardware of gamma camera lead to an obvious increase of detector performance, the final reconstructed image is still strongly restricted by reconstruction algorithms. In this work, an experiment evaluation of four popular algorithms, i.e., truncated Center-of-Gravity (TCOG), Raise-to-Power (RTP), Least Squares Estimator based on Particle Swarm Optimization (PSO-LSE) and Gaussian fitting (GF), for estimating the position of scintillation events detected by scintillation crystal array based on charge projection readout is performed. The detector of the gamma camera consists of a 22 × 22 array of CsI(Tl) scintillation crystals and an 8 × 8 matrix of SiPM pixels. The readout circuit, known as symmetric charge division (SCD) circuit, reduces an 8 × 8 array of signal channels into 8+8 signal channels coming from rows and columns projections. The imaging performances, in terms of flood image, average peak-to-valley ratio of line profile, useful field-of-view (UFOV) and position linearity response are measured. The result indicates that the four presented algorithms show good applicability for charge projection readout. RTP and PSO-LSE algorithms perform better in pixel identification of flood image and peak-to-valley of line profile, and PSO-LSE and GF methods are helpful to increase the UFOV. Among the four implemented reconstruction algorithms, PSO-LSE is a potential and promising algorithm that allows achieving excellent pixel identification of flood image, peak-to-valley ratio of line profile, spatial resolution, UFOV and position linearity response at the same time. The application of the PSO-LSE algorithm may offer the possibility to obtain high-quality reconstructed image in scintillation crystal array based on charge projection readout. [ABSTRACT FROM AUTHOR]

Quality control in a nuclear medicine department plays an important role in providing quality care for patients. Closely monitoring the uniformity values on extrinsic quality control can give insight into problems outside typical equipment issues. This facility noticed increasing uniformity values along with a photopenic image artifact. The detector required photocoupling gel replacement and a full rebuild by service engineers. This process required time for the rebuild and time for the gel to set. Another adjustment of the voltage to the photomultiplier tubes (PMTs) was required due to photocathode excitation in every cathode in every PMT in that detector. After the detector was rebuilt, the voltage was retuned with the field service engineers' knowledge that the PMTs would need to be retuned due to this excitation. Communication and understanding of equipment problems in aging γ-cameras can lead to proper equipment use and better quality in nuclear medicine departments. [ABSTRACT FROM AUTHOR]

Coded-aperture gamma-ray imaging has great application value in the fields of nuclear security, nuclear facility decommissioning, and decontamination verification. However, conventional reconstruction methods cannot handle the signal-independent noise. In this paper, a coded-aperture imaging reconstruction method based on convolutional neural network (CNN) was proposed to improve the performance of image reconstruction and enhance the source position recognition ability of imaging systems. In addition, a compact gamma camera based on cadmium zinc telluride (CZT) pixel detector and uniformly redundant array (MURA) mask was modeled. Monte Carlo simulation data were used to train CNN and test the performance of this method. Furthermore, the reconstruction of the CNN method and the correlation analysis method with different radioactive sources and measurement conditions were compared. Results show that the proposed method can suppress the reconstructed image noise well. The reconstructed images have higher contrast-to-noise ratio (CNR) than the correlation analysis method in radioactive source location. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the feasibility of short whole-body bone scan acquisition times using a novel gamma camera with cadmium-zinc-telluride (CZT) semiconductor detectors. Methods: We retrospectively enrolled 78 consecutive patients with prostate cancer who underwent bone scintigraphy using a whole-body gamma camera with CZT detectors. After acquisition of list-mode data with 180 s per bed position, anterior and posterior whole-body images were reconstructed using the first 5%, 10%, 25%, 50%, 75% and 100% of the list-mode data. Two experienced nuclear medicine physicians interpreted the images, and interrater agreement and the diagnostic value of the images were determined. Quantitative artificial neural network (ANN) values, bone scan indexes (BSI) and hotspot numbers (HsN) were also calculated by automated diagnostic software. Results: Excellent interrater reliabilities of the visual assessments were obtained for the 100%, 75%, 50%, and 25% images (κ = 0.88, 0.88, 0.88 and 0.88, respectively). The 5% images also showed high diagnostic value (sensitivity 0.94, specificity 0.84 and accuracy 0.86). Intraclass correlation coefficients (ICC) between the 100% images and the reduced acquisition time images were evaluated in quantitative analyses, and excellent correlations were observed for ANN value in the 75% images (ICC 0.77), for BSI in all the reduced acquisition time images (75%, 50%, 25%, 10% and 5%; ICC 0.99, 0.99, 0.99, 0.96 and 0.75, respectively), and for HsN in the 75%, 50%, 25% and 10% images (ICC 0.99, 0.99, 0.98 and 0.90, respectively). Conclusion: Whole-body gamma cameras with CZT detectors have the potential to reduce image acquisition times and the dose of radioisotope injected for bone scans. [ABSTRACT FROM AUTHOR]

Introduction: The gamma cameras, based on scintillation crystal followed by an array of photomultiplier tubes (PMTs), play a crucial role in nuclear medicine. The use of square PMTs provides the minimum dead zones in the camera. The camera with square PMTs also reduces the number of PMTs relative to the detection area. Introduction of a positioning algorithm to improve the spatial resolution in the detector with square PMT have been of interest in recent years. Methods: In this study, the maximum-likelihood and correlated signal enhancement positioning methods were implemented in a camera with square PMTs. The developed camera consists of 3/8" thick monolithic NaI(Tl) crystal coupled to the array of 76mm sized PMTs. The comparison is based on measuring full width at half maximum (FWHM) and standard deviation of FWHM of point sources in a 15×15 grid of samples with 2-mm grid spacing, produced using MLE and CSE positioning methods. Results: The intrinsic spatial resolution in (x, y) directions was (3.8, 3.8), (4.3, 4.5) mm for CSE and MLE methods respectively. Also, the standard deviations was almost the same in both methods (0.5 and 0.6 for CSE and MLE respectively). Although by applying MLE method, the resolution degrades by 16% but the produced image introduced acceptable quality. Conclusion: The results show the MLE method presented acceptable performance in comparison to CSE method as reference in the detector with large square PMTs. Note that the MLE method does not require any linearity correction process because it can estimate the exact position of events. [ABSTRACT FROM AUTHOR]

Single-photon emission computed tomography/computed tomography (SPECT/CT) is an already established nuclear imaging modality. Co-registration of functional information (SPECT) with anatomical images (CT) paved the way to the wider application of SPECT. Recent advancements in quantitative SPECT/CT have made it possible to incorporate quantitative parameters, such as standardized uptake value (SUV) or %injected dose (%ID), in gamma camera imaging. This is indeed a paradigm shift in gamma camera imaging from qualitative to quantitative evaluation. In fact, such quantitative approaches of nuclear imaging have only been accomplished for positron emission tomography (PET) technology. Attenuation correction, scatter correction, and resolution recovery are the three main features that enabled quantitative SPECT/CT. Further technical improvements are being achieved for partial-volume correction, motion correction, and dead-time correction. The reported clinical applications for quantitative SPECT/CT are mainly related to Tc-99m-labeled radiopharmaceuticals: Tc-99m diphosphonate for bone/joint diseases, Tc-99m pertechnetate for thyroid function, and Tc-99m diethylenetriaminepentaacetic acid for measurement of glomerular filtration rate. Dosimetry before trans-arterial radio-embolization is also a promising application for Tc-99m macro-aggregated albumin. In this review, clinical applications of Tc-99m quantitative SPECT/CT will be discussed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Medical Imaging & Radiation Sciences is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Background Gamma camera count rate saturation and high-rate dead time are the most important problems of quantitative measurement in dosimetric studies. In this study, we aimed to assess an algorithm for correction of the measured counting rates in the entire energy spectrum (327–400 keV) for camera dead-time effects. Methods In our study, whole body (WB) scan was performed by using a tissue-equivalent phantom, and that the radioactive Iodine (I-131) source with activities of 0.3, 0.6, 1.2, 1.5, 2.07, 2.7, 3.7, and 5.55 GBq was applied. WB scans of the 20% width energy windows were acquired for 420 s. Results Camera dead-time parameters were obtained from different activities of I-131 in a tissue-equivalent thyroid Phantom, then the saturation curve and coefficients α and β were obtained by using those parameters. Conclusions We concluded that in high-administered activity, it is possible to determine actual count rate of the system in saturation areas. Operation and accuracy of our gamma camera were determined for high activities of iodine-131, which can contribute to various applications of dosimetry in different fields. [ABSTRACT FROM AUTHOR]

The sensitivity and specificity of breast cancer screening with mammography in dense breasts are very low, and increasing attention has been paid to breast density and screening in highrisk groups. Therefore, a supplemental screening modality is needed. Mammography and supplementary ultrasound screening are mainly based on the differences between cancerous and normal breast parenchyma on an anatomical basis, whereas breast-specific gamma imaging is a functional imaging approach examining the physiological phenomena of blood flow and mitochondrial activity, which are increased in cancer cells. The purpose of this review is to discuss the diagnostic methods, clinical results, clinical application, and considerations of breast cancer screening with breast-specific gamma imaging using 99mTc-sestamibi. [ABSTRACT FROM AUTHOR]

Purpose: Routine quarterly quality assurance (QA) assessment of single photon emission computed tomography (SPECT) systems includes analysis of multipurpose phantoms containing spheres and rods of various sizes. When evaluated by accreditation agencies, criteria applied to assess image quality are largely subjective. Determining a quantified image characteristic metric that emulates human reader impressions of image quality could be quite useful. Our investigation was conducted to ascertain whether image texture analysis metrics, such as those applied to PET scans to detect neoplasms, could prove helpful in linking qualitative statements of phantom sphere and rod visibility to quantified parameters. Because it is not obvious whether it is preferable to submit reconstructions to accrediting agencies performed using typical clinical (CLIN) protocol processing parameters or to follow agencies' filtered backprojection (FBP) suggestions, we applied texture analysis metrics to determine the degree to which these choices affect equipment capability assessment. Methods and materials: Data were processed retrospectively for 125 different Tc‐99 m SPECT scans of standardized phantoms for 14 rotating Anger detector systems as part of routine quarterly QA. Algorithms were written to compute several classes of image metrics: quantile curve metrics, image texture analysis gray‐level co‐occurrence matrix (GLCM) metrics, contrast metrics, and count histogram metrics. For qualitative image scores, two experienced physicists independently graded sphere and rod visibility on a 5‐level scale and assigned dichotomous visibility scores, without knowledge of quantified texture analysis metrics or each other's readings. The same phantom was used to collect 15 additional data sets with two dual‐detector SPECT/CT systems, reconstructed both by FBP parameters that have been suggested by accrediting agencies and by manufacturers' default settings for CLIN SPECT/CT bone imaging protocols by ordered subsets expectation maximization (OSEM), incorporating attenuation correction using the CT scan. Image characteristics metrics were compared for FBP and CLIN reconstructions. Results: For spheres, the metric with the strongest rank correlation with 5‐level scale readings was the quantile curve slope (ρ = 0.83, P < 0.0001), while for rods it was GLCM Energy normalized to the maximum GLCM Energy value (EnergyNorm) (ρ = −0.88, P < 0.0001). Compared to dichotomous readings, the metric with the highest ROC area under curve (AUC) for spheres was the quantile curve slopes (AUC = 96 ± 1%, sensitivity = 91%, specificity = 90%), and for rods was EnergyNorm (AUC = 98 ± 1%, sensitivity = 92%, specificity = 95%). Image contrast was higher for all sphere sizes and rod EnergyNorm was lower for sectors of intermediate‐sized rods for FBP compared to CLIN reconstructions, in agreement with more rods judged to be visible from FBP than CLIN reconstructions (47% vs 33%, P = 0.002). Conclusions: When preparing to submit quality assurance images of standardized phantoms to accrediting agencies, a reliable gauge of sphere and rod visibility can be predicted accurately using quantified reader‐independent image texture analysis metrics, which also provide a useful basis for choosing among alternative image reconstruction options. [ABSTRACT FROM AUTHOR]

The one of the aim of nuclear medicine is diagnosis of an abnormal metabolic activities in target organs. In a routine nuclear medicine imaging procedure, a radiopharmaceutical is used. Radiopharmaceutical’s radionuclide part emits gamma radiation. This radiation is dedected by Gamma Camera or Single Photon Emission Computed Tomography (SPECT). A computed tomography (CT) device was added to the SPECT(SPECT- CT). To combine anatomical images. Image quality of this device is important for accurate diagnosis and treatment of diseases. By means of quality control tests, performance changes of device are dedected. A various quality control parameters such as uniformity, sensivity, resolution, linearity have been developed for Gamma cameras, SPECT. Quality control test results are should be verify by comparing acceptable results. In this study, quality control tests of SPECT-CT are performed as proposed by the National Electrical Manufacturers Association ( NEMA) and it was aimed to investigate some correction methods. [ABSTRACT FROM AUTHOR]

Abstract In the framework of a national funded program for nuclear safety, a first prototype of portable gamma camera was built and tested. It integrates a Caliste-HD CdTe-hybrid detector designed for space X-ray astronomy coupled with a new system-on-chip based acquisition system (FPGA and ARM microprocessor) and thermo-electrical coolers for a use at room temperature. The complete gamma part of the camera fits in a volume of 15 × 15 × 40 cm 3 for a mass lower than 1 kg and a power consumption lower than 10 W. Localization and spectro-identification of radionuclides in a contaminated scene were demonstrated during several test campaigns. A new generation of system is under development taking into account feedback experience from in-situ measurements and integrating a new generation of sensor cost-optimized by industrial applications called Caliste-O. Caliste-O holds a 16 × 16 pixel detector of 14 × 14 mm 2 and 2 mm thick with 8 full-custom front-end IDeF-X HD ASICs. Two prototypes were fabricated and tested. The paper will present the results of in-situ measurements with the first gamma camera, the spectroscopic performance of Caliste-O and the design of the second generation of gamma camera which aims for real time imaging and spectro-identification. [ABSTRACT FROM AUTHOR]

Single photon imaging still remains the most commonly used imaging method in nuclear medicine to date, usually employing a gamma camera furnished with a parallel hole (PH) collimator. Using this type of collimator implies that both the size of the field of view (FOV) and the sensitivity are invariant with the distance from the object plane. Otherwise, the spatial resolution is inversely proportional to the distance from the object plane. In the present study, a modified parallel hole design, i.e., the parallel jagged hole (PJH), is introduced with the aim to improve the relationship between the spatial resolution and the sensitivity of a standard PH collimator. Quantitative characteristics of three PJH test samples were assessed experimentally as well as by applying simulation with the help of the MCNP5 code and using analytical approximation. In addition, the overall qualitative imaging performance was evaluated with the help of a custom-built planar phantom. While the sensitivity of one of the PJH test samples was very close to that of the corresponding PH design, its spatial resolution appeared to be superior by some 5–12%. Another test sample that exhibited nearly identical spatial resolution to its reference PH design was found to have approximately 35% higher sensitivity. So far, the experimental results as well as the outcomes obtained by simulation and by analytical approximation were found to be in good agreement among them what suggests that proposed PJH design could improve the imaging quality beyond that of the standard PH collimator. • PJH collimators improve the tradeoff between spatial resolution and sensitivity. • The jags modify the PSF shape when added to PH collimator. • PJH collimators improve spatial resolution while avoiding sensitivity loss. • PJH collimators increase sensitivity while preserving the spatial resolution. [ABSTRACT FROM AUTHOR]

Positron emission tomography (PET) and single-photon emission-computed tomography (SPECT) are important nuclear-medical imaging tools in diagnosing cancers and creating effective treatment plans. Commercially imaging systems are operated externally and can create 3D images of the whole body or of specific organs by rotating the gamma-ray detectors, and then employing software to reconstruct the 3D images from the multiple 2D projections at different angles of view. However, their uses in intraoperative environments or for imaging specific small organs, e.g., the prostate, ovary, and cervix, are limited because of their bulky designs and the long working-distance, hence causing low efficiency and poor spatial-resolution. In such situations, compact imaging devices, e.g., the trans-rectal gamma camera developed at Brookhaven National Laboratory (BNL) and Hybridyne Imaging Technologies, are preferable for detecting intra-prostatic tumors. The camera uses pixilated cadmium zinc telluride (CdZnTe) detectors with a matched parallel-hole collimator. However, their lack of 3D imaging capability limits their use in clinics, because the acquired images cannot be interpreted easily due to missing depth information. Given the constraint on space in such operations, the traditional 3D-image acquisition methods are impractical. For this reason, we designed an interwoven collimator dedicated for 3D imaging using an endocavity probe. This novel collimator allows us to take two or multiple views of a specific organ or tissue without rotating the camera. At the first stage of design for the collimator, we carried out Monte-Carlo simulations to study the response of the collimator and the attached detectors to gamma rays, and then developed a maximum-likelihood-based algorithm for reconstructing 3D images. In this paper, we detail our modeling of the collimator on a cluster Linux computer, and discuss the imaging capability of this novel collimator.

The prompt response to emergency situations involving suspicion of intakes of radionuclides requires the use of simple and rapid methods of internal monitoring of the exposed individuals. The use of gamma cameras to estimate intakes and committed doses was investigated by the Centers for Disease Control and Preventions (CDC) of the USA in 2010.The present study aims to develop a calibration protocol for gamma cameras to be applied on internal monitoring based on urine samples to evaluate the incorporation of high-energy photon emitting radionuclides in emergency situations. A gamma camera available in a public hospital located in the city of Rio de Janeiro was calibrated using a standard liquid source of 152Eu supplied by the LNMRI of the IRD. “Efficiency vs Energy” curves at 2 and 10 cm were obtained. Calibration factors, Minimum Detectable Activities and Minimum Detectable Effective Doses of the gamma camera were calculated for 131I and 137Cs. The gamma camera evaluated in this work presents enough sensitivity to detect activities of such radionuclides at dose levels suitable to assess suspected accidental intakes.