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Effect of Source to Camera Distance and Count Rate on Intrinsic Uniformity of SPECT Gamma Camera  [PDF]
Sabrina Sarah, Mahidul Haque Prodhan, Kawsar Hamid, Fazlul Huq
Open Journal of Medical Imaging (OJMI) , 2015, DOI: 10.4236/ojmi.2015.52012
Abstract: In this research, the excellent parameter for regular Quality Control (QC) testing of intrinsic uniformity for dual-head Single Photon Emission Computed Tomography (SPECT) gamma camera is determined. The integral and differential intrinsic uniformity tests for both Useful Field Of View (UFOV) and Centre Field Of View (CFOV) were done by insertion a point-source of 99mTc in front of the detectors with detached collimators to measure the effect of source to camera distance and a count rate on intrinsic uniformity. The result reveals that the best intrinsic uniformity image is obtained at source-to-camera distance of 3 m and a count rate between 16 and 60 M.
Single- versus dual-head SPECT for detection of myocardial ischemia and viability in a large study population
J. Bucerius,H. Ahmadzadehfar,A.Y. Joe,I. Lindstaedt
Iranian Journal of Nuclear Medicine , 2006,
Abstract: Background: As single-head data acquisition for Thallium-201 myocardial single photon emission computed tomography (SPECT) is a frequently used method mainly in the outpatient medical care as well as in smaller non-university hospitals, comparison to dual-head data collection is a still discussed issue mainly with regard to quality control and -assurance. Methods: A total of 1,334 patients undergoing thallium-201 myocardial SPECT for diagnosis of myocardial ischemia and / or viability has been retrospectively analyzed. In 554 patients a single-head gamma-camera (360° rotation) has been applied, whereas a dual-head gamma-camera has been used in 780 patients (180° rotation). 426 patients received both myocardial SPECT as well as coronary angiography. The diagnostic efficacy of both SPECT cameras and applied acquisition techniques were analyzed. Results: The positive predictive value for diagnosis of myocardial scar tissue was significantly higher for dual-head- as compared to single-head acquisition. Among the 426 patients undergoing diagnosis of myocardial ischemia significant differences have only been found with regard to the specificity being higher in the single-head acquisition. Diagnosis of myocardial ischemia related to a distinct myocardial perfusion region showed a significantly higher sensitivity of dual-head acquisition for the LAD-perfusion area, whereas specificity was significantly higher for single-head acquisition. Conclusion: Our results indicate a beneficial effect of dual-head data collection with regard to the sensitivity of the diagnosis of myocardial ischemia. In contrast, single-head data acquisition was superior with regard to the specificity. As such, there is no significant benefit of one of the compared camera systems and acquisition techniques. However, newer techniques such as transmission attenuation correction and / or iterative reconstruction should be implemented and further improve image quality and diagnostic value of myocardial perfusion SPECT.
Coincidence gamma camera imaging; a comparison between the two modes of imaging
F. Abbaspour,A. Bitarafan-Rajabi,H. Rajabi,F. Rastgou
Iranian Journal of Nuclear Medicine , 2006,
Abstract: Objectives: Scintillation cameras with the options for the detection and localization of positron annihilation in the coincidence mode may be considered as an intermediate device between conventional nuclear medicine and modern PET systems. This relatively inexpensive option offers an opportunity for the impoverished centers to perform some epigonic PET studies at acceptable quality. Due to great difference between photon energy used in coincidence and conventional modes, optimizing the performance of the system in both modes is a big challenge. In this study we acquired similar images in both modes to investigate if the camera is really optimized for both acquisition modes. Methods: The dual detector gamma camera (Vertex Molecular Coincidence Detection, ADAC Laboratories, and Milpitas, CA) equipped with a 5/8-inch crystal detector was investigated. In coincidence mode all photopeak-to-photopeak events as well as the photopeak-to-Compton scatter events were used. The energy windows were set at 511 kev/30% for the18F photopeak and 310 kev/30% for the Compton events. The SPECT studies were performed with VXHR collimator and matrix size 128*128 using 99mTc. The images of two dimensional brain phantom, SPECT resolution phantom and NEMA line-spread phantom were acquired in both modes five times each. Each dataset was rebinned using single slice rebinning and reconstructed using filtered backprojection and also ordered subset exception maximization iterative algorithm. Attenuation correction (by calculated factors, μ=0.095 cm-1) and random correction techniques were used in this study. Results: We investigated the best reconstruction condition for all images based on the spatial resolution (minimum FWHM and FWTM), contrast (highest) and quality (visual inspection) of the images. For each phantom the supreme quality images were compared. Regarding the resolution, contrast and quality the images that were acquired in coincidence mode were significantly (p-value <0.001) better than the similar images in conventional mode. Conclusion: The high cost of a PET system has been a major constraint to the clinical use of it. Though not a real competitor, a coincidence gamma camera may be useful when a PET system is not available. However it should not be ignored that a gamma camera can not be optimized to work in a wide rang of photon energy. Since now the most emphasis has been the inferior quality of coincidence image compared to PET images. Nevertheless the quality of such system in conventional mode should also be considered.
A clinical gamma camera-based pinhole collimated system for high resolution small animal SPECT imaging
Mejia, J.;Galvis-Alonso, O.Y.;Castro, A.A.de;Braga, J.;Leite, J.P.;Sim?es, M.V.;
Brazilian Journal of Medical and Biological Research , 2010, DOI: 10.1590/S0100-879X2010007500128
Abstract: the main objective of the present study was to upgrade a clinical gamma camera to obtain high resolution tomographic images of small animal organs. the system is based on a clinical gamma camera to which we have adapted a special-purpose pinhole collimator and a device for positioning and rotating the target based on a computer-controlled step motor. we developed a software tool to reconstruct the target’s three-dimensional distribution of emission from a set of planar projections, based on the maximum likelihood algorithm. we present details on the hardware and software implementation. we imaged phantoms and heart and kidneys of rats. when using pinhole collimators, the spatial resolution and sensitivity of the imaging system depend on parameters such as the detector-to-collimator and detector-to-target distances and pinhole diameter. in this study, we reached an object voxel size of 0.6 mm and spatial resolution better than 2.4 and 1.7 mm full width at half maximum when 1.5- and 1.0-mm diameter pinholes were used, respectively. appropriate sensitivity to study the target of interest was attained in both cases. additionally, we show that as few as 12 projections are sufficient to attain good quality reconstructions, a result that implies a significant reduction of acquisition time and opens the possibility for radiotracer dynamic studies. in conclusion, a high resolution single photon emission computed tomography (spect) system was developed using a commercial clinical gamma camera, allowing the acquisition of detailed volumetric images of small animal organs. this type of system has important implications for research areas such as cardiology, neurology or oncology.
Quality control of a virtual SPECT simulated by SimSET
S. Rasaneh,H. Rajabi,F. Kalantari
Iranian Journal of Nuclear Medicine , 2006,
Abstract: Objectives: Simulation is the first step for improving the imaging tests and developing the imaging systems. SIMSET is a routine powerful simulation software for simulating nuclear medicine systems specially SPECT. It is necessary that the parameters of these simulation software be accuracy and according to standards in real systems. In this study we considered the SIMSET software with intrinsic quality control tests. Methods: We perform four routine intrinsic quality control tests (uniformity, spatial resolution, spatial linearity, energy resolution) in a virtual SPECT system that was simulated by SimSET. We also used the NCAT softwares to produce the phantoms of quality control. These tests were performed according to the NEMA methods. The calculations were done in mathlab and for more accuracy all the procedures were repeated 5 times. Results: We acquired integral and differential uniformity less than 1% for 1000 counts per pixel, spatial resolution less than 3 cm, spatial linearity less than 0.02% and energy resolution was exactly the same as the default value that be set. Conclusion: All the parameters that we calculated were according NEMA standards. But the calculated values were ideally less than the parameters in real SPECT systems. It shows that it needs more study to extend the result of simulating to real condition.
Control de calidad mínimo de los instrumentos de imágenes en Medicina nuclear.  [cached]
Cabrejas, Mariana L. de,Giannone, Carlos,Arashiro Jorge
Alasbimn Journal , 1999,
Abstract: Se presenta un Programa Básico de Control de Calidad para instrumentos de imágenes por medicina nuclear, que permite disponer de un seguimiento documentado externo a cada laboratorio/centro, de los parámetros de funcionamiento de los sistemas de cámara gamma planar y SPECT. Este Programa considera un número mínimo e imprescindible de controles, la frecuencia de los mismos y el análisis periódico por un grupo independiente de los centros que participen en el programa. Las pruebas de control de calidad se han simplificado reduciendo la necesidad de fantomas y facilitando el procesamiento. La adherencia al Programa permitirá la evaluación continua, global de la calidad de los servicios de medicina nuclear, como también documentar individualmente cada performance avalando requisitos exigidos para la participación en estudios clínicos multicéntricos y multinacionales.A simplified, basic Quality Control Programme for Nuclear Medicine instruments (gamma camera and SPECT) is presented. The Programme considers an external follow-up of each laboratory, defines the minimum number of required tests, simplifies the phantoms and the processing conditions and proposes the frecuency at which each test has to be performed. Participation in this Programme will help to assess the present grobal quality of Nuclear Medicine in the countries, improve it and allow follow-up of performance parameter requirements needed to participate in multicentric and multinational clinical trials.A survey carried out by our group in 1997, states that very good performance is found for SPECT systems in Argentina. However these results correlate more with the low aging of the instruments, than with the acceptance of a quality control programme. Only the inclusion of the QC methodology as a routine of each lab, assures quality of the clinical studies.
Quantitative Accuracy of Low-Count SPECT Imaging in Phantom and In Vivo Mouse Studies  [PDF]
Ciara M. Finucane,Iain Murray,Jane K. Sosabowski,Julie M. Foster,Stephen J. Mather
International Journal of Molecular Imaging , 2011, DOI: 10.1155/2011/197381
Abstract: We investigated the accuracy of a single photon emission computed tomography (SPECT) system in quantifying a wide range of radioactivity concentrations using different scan times in both phantom and animal models. A phantom containing various amounts of In-111 or Tc-99m was imaged until the activity had decayed close to background levels. Scans were acquired for different durations, employing different collimator pinhole sizes. VOI analysis was performed to quantify uptake in the images and the values compared to the true activity. The phantom results were then validated in tumour-bearing mice. The use of an appropriate calibration phantom and disabling of a background subtraction feature meant that absolute errors were within 12% of the true activity. Furthermore, a comparison of in vivo imaging and biodistribution studies in mice showed a correlation of 0.99 for activities over the 200?kBq to 5?MBq range. We conclude that the quantitative information provided by the NanoSPECT camera is accurate and allows replacement of dissection studies for assessment of radiotracer biodistribution in mouse models. 1. Introduction In vivo imaging of radiopharmaceutical uptake by single photon emission tomography (SPECT) in small animal models is an important tool with great potential for the development of new and improved radiopharmaceutical agents for targeted diagnosis and therapy of cancer [1–3]. In addition to providing high-quality images for qualitative interpretation, accurate quantification is required to determine the amount of uptake in tissues of interest and the pharmacokinetics of a compound in vivo [4]. SPECT studies are advantageous as they reduce the number of animals required compared to necropsy studies and allow longitudinal studies in the same animal [5]. Radionuclide imaging techniques such as SPECT and positron emission tomography (PET) are widely used for preclinical radiopharmaceutical development [6, 7] because of the possibility of direct translation of results from preclinical laboratories to the human clinical setting [8]. PET imaging has been seen as the more accurately quantifiable technique due to its higher sensitivity; however, development of SPECT imaging systems in recent years has led to higher resolution and sensitivity capabilities, making it an attractive option for quantitative in vivo imaging using longer-lived gamma-emitting radionuclides [8]. Three types of radionuclide quantification study are described in the literature. The first is a semiquantitative comparison of different regions of the image such as measurement of
Results of the Measurement of the Collimator Hole Angulation for Different Collimators of SPECT with Adaptive Quality Control Phantom  [PDF]
Hossein Zamani Zeinali, Ehsan Masumi Goodarzi, Hamid Ravanbakhsh, Ali Asgher Sardarpour, Narjes Abagheri Mahabadi, Soghra Moradkhani, Fatemeh Dolatshah, Davood Rahi
Modern Instrumentation (MI) , 2012, DOI: 10.4236/mi.2012.14007
Abstract: The Adaptive Quality Control Phantom (AQCP) is the computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce any spatial distribution of gamma rays to perform the QC Tests such as the Collimator Hole Angulation (CHA) of Single Photon Emission Computer Tomography (SPECT). The collimator hole angulation for seven collimators were measured with the method by using a point source and computer-controlled cylindrical positioning. In this method the displacement of the image of a point source examined as the AQCP move point source vertically away from the collimator face. The results of the high-accuracy measurement method of CHA show that the measurement accuracy for absolute angulation errors is better than ±0.024°. The Root Mean Square (RMS) of CHA for LEHR, LEHS, LEUHR, MEGP-250, MEGP-300, MEGP-360 and HEPH collimators of SMV dual heads camera were measured to be 0.290°, 0.292°, 0.208°, 0.194°, 0.181°, 0.177°, 0.150°, respectively. The Root Mean Square (RMS) of CHA for LEGP, MEGP and HEGP collimators of GE Millennium MG were measured to be 0.154°, 0.220° and 0.202° respectively. It is to be added in this connection that the measured RMS of CHA for LEHR collimator with the distance variation from the collimator’s surface +/– 1 mm has been varied +/– 0.04 degree.
The Precise Methods for the Measurement of Collimator Hole Angulation and Center of Rotation of SPECT by Adaptive Quality Control Phantom  [PDF]
Hossein Zamani Zeinali, Mehran Ataee, Hamid Ravanbakhsh, Ehsan Masumi Goodarzi, Samana Ghoreishi, Gholamreza Raisali
World Journal of Nuclear Science and Technology (WJNST) , 2014, DOI: 10.4236/wjnst.2014.44026
Abstract: The Adaptive Quality Control Phantom (AQCP) is a computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce a spatial distribution of gamma rays to perform QC Tests such as the Collimator Hole Angulation (CHA) and the Center of Rotation (COR) of Single Photon Emission Computer Tomography (SPECT). The collimator hole angulation for six collimators was measured using a point source and a computer-controlled cylindrical positioning system. In this method, the displacement of the image of a point source was examined as the AQCP was moving point source vertically away from the collimator face. The results of the high-accuracy measurement method of CHA show that the measurement accuracy for absolute angulation errors is better than ±0.024°. The Root Mean Square (RMS) of CHA for LEHR, LEHS and LEUHR collimators of SMV dual heads camera and LEGP, MEGP and HEGP of GE Millennium MG were evaluated to be 0.290°, 0.292°, 0.208°, 0.154°, 0.220° and 0.202°, respectively. It is to be added in this connection that the evaluated RMS of CHA for LEHR collimator with the distance variation from the collimator’s surface ±1 mm has been varied ±0.04 degree. A new method for the center of rotation assessment by AQCP is introduced and the results of this proposed method as compared with the routine QC test and their differences are discussed in detail. We defined and measured a new parameter called Dynamic Mechanical Error (DME) for applying the gantry motion correction.
Evaluation of performance quality of SPECT camera in Sharyati Hospital of Tehran University of Medical Sciences
Takavar A
Iranian Journal of Nuclear Medicine , 2001,
Abstract: In nuclear medicine, there are two methods of imaging, planar and tomography. Single photon emission computerized tomography (SPECT) shows better image details and therefore is influenced more by image parameters such as resolution, uniformity, sensitivity, etc. Manufacturers provide customers with data which are obtained by complicated and sometimes secret methods. Marketing companies test and verify these data and buyers perform acceptance testing on installation of system. Since acceptance testing is not usually done in our country, follow up of system performance and therefore setting up of a comperehensive quality control program faces difficulty. In this research which was done sometimes after installation, evaluation of SPECT system was carried out and data obtained were compared with those of manufacturer catalogue. It was found that in most cases our figures do not correspond to those of manufacturer catalogue, therefore acceptance testing using standard and precision devices being carried out by trained personnel is strongly recommended.
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