Purpose: Micro Single Photon Emission Computed Tomography (Micro-SPECT) system has recently been introduced on nuclear medicine in the preclinical and research in which NaI (Tl) and Cadmium Telluride (CdTe) are used as the gamma-ray detectors with more generally use of NaI (Tl). The present study aimed to evaluate different thicknesses of the NaI (Tl) and (CdTe) detectors on functional parameters of a micro-SPECT system. Materials and Methods: A Micro-SPECT system with CdTe semiconductor detector and a hexagonal parallel hole collimator with a hole diameter of 0. 11 mm, high of 24. 05 mm, and septal thickness of 0. 016 mm was simulated by Simulating Medical Imaging Nuclear Detectors (SIMIND) Monte Carlo program. The system performance was assessed by comparing the functional parameters, including system efficiency, sensitivity, energy and spatial resolution with the NaI (Tl) detector. The simulated scans of a 99mTc point source, a digital micro-Jacszack phantom, and a voxelized MOBY mouse phantom with the system were prepared to evaluate image quality. Results: The functional parameters,sensitivity, efficiency, planar spatial resolution, and image contrast of CdTe detector were determined 1. 4, 1. 2, 1. 7, and 1. 8 times higher than those of NaI (Tl), respectively. Moreover, the calculated energy resolution of CdTe and NaI (Tl) detectors was obtained 6. 2% and 10. 2% at 141 KeV, respectively. In the filtered back projection (FBP) reconstructed images of the micro-Jacszack phantom, minimum detectable size of the cold rods with CdTe and NaI (Tl) detectors were obtained 0. 79 mm and 0. 95 mm, respectively. Conclusion: The imaging system with a 5. 5 mm thickness CdTe detector provided better image quality and showed considerable efficiency.

Introduction: Detecting scattered photons in the photo peak window degrades the image contrast and quantitative accuracy of single-photon emission computed tomography (SPECT) imaging. This study aimed to determine optimal main-and sub-energy windows for Triple Energy Window (TEW) in In-111. Material and Methods: We used the simulating medical imaging nuclear detectors (SIMIND) program to simulate the Siemens SYMBIA gamma camera equipped with a medium energy (ME) collimator. We also used the SIMIND Monte Carlo program to generate theIn-111SPECT projection data of the Jaszczak phantom. The phantom consisting of six spheres with different diameters (9. 5, 12. 7, 19. 1, 15. 9, 25. 4, and 31. 8 mm) was used to evaluate the image contrast. Geometric, scatter, and penetration fraction, point spread functions, and contrast curves were drawn and compared. Results: The results showed that the 171keVphotopeak compared to the 245keVphotopeak yielded the best results with an ME collimator when the TEW scatter correction method was applied. The reason can be the large amount of scatter and penetration from the photo peak and the collimator for the 245keVphotopeak window. Conclusion: With the TEW scatter correction method, it is better to use a 171keVphotopeak window because of its better spatial resolution and image contrast.

Introduction: Quality control is an important phenomenon in nuclear medicine imaging. A Jaszczak SPECT Phantom provides consistent performance information for any SPECT or PET system. This article describes the simulation of a Jaszczak phantom and creating an executable phantom file for comparing assessment of SPECT cameras using SIMIND Monte Carlo simulation program which is well-established for SPECT.Materials and Methods: The simulation was based on a Deluxe model of Jaszczak Phantom with defined geometry. Quality control tests were provided together with initial imaging example and suggested use for the assessment of parameters such as spatial resolution, limits of lesion detection, and contrast comparing with a Siemens E. Cam SPECT system.Results: The phantom simulation was verified by matching tomographic spatial resolution, image contrast, and also uniformity compared with the experiment SPECT of the phantom from filtered back projection reconstructed images of the spheres and rods. The calculated contrasts of the rods were 0.774, 0.627, 0.575, 0.372, 0.191, and 0.132 for an experiment with the rods diameters of 31.8, 25.4, 19.1, 15.9, 12.7, and 9.5 mm, respectively. The calculated contrasts of simulated rods were 0.661, 0.527, 0.487, 0.400, 0.23, and 0.2 for cold rods and also 0.92, 0.91, 0.88, 0.81, 0.76, and 0.56 for hot rods. Reconstructed spatial tomographic resolution of both experiment and simulated SPECTs of the phantom obtained about 9.5 mm. An executable phantom file and an input phantom file were created for the SIMIND Monte Carlo program.Conclusion: This phantom may be used for simulated SPECT systems and would be ideal for verification of the simulated systems with real ones by comparing the results of quality control and image evaluation. It is also envisaged that this phantom could be used with a range of radionuclide doses in simulation situations such as cold, hot, and background uptakes for the assessment of detection characteristics when a new similar clinical SPECT procedure is being simulated.

Background: Various variance reduction techniques such as forced detection (FD) have been implemented in Monte Carlo (MC) simulation of nuclear medicine in an effort to decrease the simulation time while keeping accuracy. However most of these techniques still result in very long MC simulation times for being implemented into routine use. Materials and Methods: Convolution-based forced detection (CFD) method as a variance reduction technique was implemented into the well known SIMIND MC photon simulation software. A variety of simulations including point and extended sources in uniform and non-uniform attenuation media, were performed to compare differences between FD and CFD versions of SIMIND modeling for I131 radionuclide and camera configurations. Experimental measurement of system response function was compared to FD and CFD simulation data. Results: Different simulations using the CFD method agree very well with experimental measurements as well as FD version. CFD simulations of system response function and larger sources in uniform and non-uniform attenuated phantoms also agree well with FD version of SIMIND. Conclusion: CFD has been  odeled into the SIMIND MC program and validated. With the current implementation of CFD, simulation times were approximately 10-15 times shorter with similar accuracy and image quality compared with FD MC.