Purpose: Noise in brain Single Photon Emission Computed Tomography (SPECT) images limits an early diagnosis of Parkinson's Disease (PD). To overcome the limitation, as an image processing approach, wavelet transformation was used to denoising the images also with a segmentation method to differentiate the basal ganglia in brain SPECT. Materials and Methods: The brain scans of the human XCAT phantom through the Simulating Medical Imaging Nuclear Detectors (SIMIND) simulated SPECT system were imported to the MATLAB toolkit for image processing. The reconstructed brain images by iterative reconstruction were de-noised through 9 methods of wavelet transformation at different levels, and then six segmentation methods were applied to differentiate the caudate and putamen. The Dice coefficient, Specificity, and Sensitivity evaluation criteria were calculated based on the adaptive thresholding of the selected images from segmentation. A ground truth image was manually marked by a clinical Nuclear medicine specialist. Results: The dice coefficient was obtained in a range from 0. 3979 to 0. 6299, as well as the specificity criterion from 0. 7682 to 0. 8168 and the sensitivity from 0. 9049 to 0. 9871. The results from adaptive threshold segmentation and the evaluation criteria showed that the best levels of the nucleuses detectability were provided by level 7 of Biorthogonal, levels 4 and 7 of Coiflet, level 6 of Daubechies, level 5 of Haar, level 6 of Morlet and level 6 of Symlet methods. Conclusion: Parkinson’s disease may be diagnosed in the early stage by an image processing approach to improve the quality of brain SPECT images.

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.

In this work, a neutron irradiating system containing six Am/Be neutron sources in a graphite moderator, which produces a relatively high and uniform thermal neutron flux in an irradiating cavity at the center of the system , has been  simulated .The thermal neutron flux in the center of the system has then been calculated and compared with experimental results  measured in a cavity at the center of a similar system .Good agreement between calculated and measured values show that true value of thermal neutron flux in this system (or any other irradiating system) can be accurately calculated by simulation method and be used for calibrating neutron Detectors and dosimeters. This system has been simulated using the MCNP Monte Carlo computer code. In the calculations, thermal neutron flux has been first calculated at various distances from a single neutron source in a graphite moderator and then calculations have been performed and results discussed  for various cases of 2, 4 and 6 neutron sources being present in the system. In addition, to investigate the effect of moderator properties on neutron flux distribution in the system, parallel calculations have been done for watermoderator, which show water is not a proper moderator for such a system.

Introduction: Most beta and gamma radiation radioisotopes used for treatment are not suitable for Imaging. The bremsstrahlung images on a conventional gamma camera helped to localize the radionuclide within and outside of the lesion. Secondary scattering of gamma rays of higher energy and bremsstrahlung causes contamination in the energy window and reducing the contrast and resolution of the images and the quantization validation of the images cannot be performed. Therefore, the accuracy of scatter correction methods is of great importance. The method involves the use of energy window, empirically selected broad bremsstrahlung energy to enhance the signal to noise ratio and a wiener restoration filter to compensate for system blur. Materials and Methods: To simulate and validate the system, a water bottle containing Phosphorus-32 (P32) radio was taken. GATE package was used to determine the spectrum of bremsstrahlung radiation from P32 inside the liver and Zubal phantom was used to model a liver. Importantly, simulations were performed in the presence of a collimator without collimator and the collimator function was calculated. Zubal Phantom was also used to model liver Imaging. The Wiener filter was used as a resolution adjuster. Results: Despite the small number of electrons reaching the collimator, a considerable spectrum is produced. Collimator function and simulated liver image were calculated. No significant change in resolution was observed after using the Weiner filter. Conclusion: The energy spectrum of the beams was altered after collimation to the collimator. Also, the shape of the energy spectrum was influenced by the type of tissue and size of the patient. The results had shown that planar gamma camera Imaging and quantitation of P32 can be done. There is no compelling reason to suggest that the Wiener filter is useful in planning a Plane.

In this paper we consider a gaseous detector and supposed, because of pass of an ionizing radiation, an electron created inside it. By numerical simulation with Monte Carlo method and concluding the impacts, scatterings and creation of secondary electrons, we find the trajectory of initial and secondary electrons. Dependence of number of secondary electrons to applied electrical field is investigated. Finally we study the dependence of number of secondary electrons to number of initial electrons created by ionizing radiation (as a measure of the radiation energy), then we try to investigate the possibility of spectrometry by this Detectors.

Purpose: Nowadays, the use of polymer composites with several metals to design and build new radiation composite shields with practical features in radiology is expanding. Materials and Methods: Three metal oxides, including Bismuth oxide (Bi2O3), Tungsten oxide (WO3), and Tin oxide (SnO2) were used as mono-metal and bimetallic compound silicon matrixes for clarification of their practical use. Monte Carlo simulation methods were used to enter the specifications of each metal in combination with silicon. The mass attenuation coefficients of the mono-and bimetallic composites were calculated in the energy ranges of 40 to 150 KeV by classification to low/ medium/high groups. Results: The results showed the beam reduction ability for both the mono-and the bimetallic composites. The mass attenuation coefficients of Bi2O3, WO3, and SnO2 at 80 KeV were 0. 38, 0. 33, and 0. 57 cm2/gr, respectively. Moreover, the Bismuth-Tin bimetallic combination at low energies and the Bismuth-Tungsten at high energies had better attenuation than the other samples. To select bimetallic compounds with a high attenuation coefficient, it is better to match the energy used in the Imaging method specifically. For example, in the 70-90 KeV energy range, the Sn-W combination had the highest beam attenuation coefficient. Conclusion: The advantage of mono-and bimetallic shields in terms of energy attenuation amount depends on beam energy and shielding metal “K-absorption” edge. In comparing the attenuation of recorded beams in low, medium, and high ranges of energy, mono-metallic Bismuth shows higher attenuation coefficients than mono-metallic Tungsten and bi-metallic Bismuth–Tungsten. Dose reduction of the bi-metallic state of Bismuth-Tin was greater than that of mono-metallic Bismuth and Tin in low energies. Also, the attenuation of the Bi-Sn composite shield in low energy was the highest amount among all silicon composite shields.

Background: The Poly-Allyl Diglycol Carbonate (PADC) detector is of particular interest for development of a fast neutron dosimeter. Fast neutrons interact with the constituents of the CR-39 detector and produce H, C and O recoils, as well as (n, a) reaction. These neutron- induced charged particles contribute towards the response of CR-39 Detectors.Material and Methods: Electrochemical etching was used to enlarge track diameter which was made by low energy recoil protons. Before electrochemical etching, a chemical etching was performed for 1 hour. The responses were also calculated by Monte Carlo simulations, using MCNPX code in different energy bins considering H, C and O recoils. The total registered efficiency and partial contributions of the efficiency, due to interactions with each constituent of CR-39, were calculated.Results: The optimized condition of etchant was obtained to be 6N KOH 15kV.cm-1, and 6 hours etching time. The obtained results show that track efficiency of CR-39 was a function of incident neutron energy. The tracks caused by O and C recoil nuclei were negligible for neutron energies lower than 1 MeV. At neutron energies lower than 1 MeV, only recoil protons would have sufficient energy to leave visible tracks. But, O and C recoils had important contributions in overall response of PADC at neutron energies of few MeV.Conclusion: The efficiency of a CR-39 based dosemeter could be calculated by MCNPX code and the results were in a good agreement with experimental results in energy range of 241Am– Be bare source and 241Am- Be was softened with a spherical polyethylene moderator of radius of 20 cm.

Introduction: The Compton scattered annihilation gammas between PET Detectors reduce spatial resolution by making an incorrect Line of Response. This paper, by presenting a new method, tried to remove these errors from PET Imaging. In this way, the Detectors were insulated so that scattered gammas from a detector can not enter other Detectors of the PET ring. Materials and Methods: First of all, the Siemens PET Biograph TM 6 scanner ring was simulated and then all Detectors of this ring were isolated to resolve this error and investigate its impact on the Response Function ofPET Detectors. Results: The analysis of the results of simulation showed that, the isolation of PET Detectors reduced counts of Detectors in the energy window, especially at the lower threshold (350 to 400 keV). This reduction with a spherical soft issue was less than without that. So that the maximum of therelative percentage difference for counts of Detectors between connect and disconnect them was 70% (in 400 keV) and 12% (in 350 keV) in the absence and presence of soft tissue, respectively. Conclusion: Although the isolation of the Detectors boosted the resolution of PET, it removed some true coincidences and reduced the sensitivity of PET; there for, it did not have much effect on image quality of PET. Also, a slight decrease in the count, with the soft tissue, shows the greater effect of the isolation of PET-Detectors in improving image quality in abdominal Imaging in comparison with other Imaging such as head and neck Imaging.

Introduction: Myocardial perfusion SPECT by 99mTc-Sestamibi and 99mTc-Tetrofosmin radiopharmaceuticals usually presents a false significant increase in the radiotracer uptake in the inferior myocardium due to the uptake in organs such as liver, bowel, stomach and biliary system. The present study evaluated a suitable Slit angle for differentiating extra-cardiac activities by Slit Slat collimation.Methods: The Siemens E.CAM gamma camera equipped with a Low Energy High Resolution (LEHR) collimator was simulated with the Simulating Medical Imaging Nuclear Detectors (SIMIND) Monte Carlo program. Following the verification of the simulation, a Slit Slat collimator was simulated for SPECT Imaging of a NURBS-based Cardiac Torso (NCAT) phantom with different Slit angels ranged from 0 to 30 degrees. The reconstructed images were qualitatively assessed with blinded observer method by three Nuclear medicine specialists.Results: The improved differentiation of the bowel activity from the cardiac was obtained by a Slit-Slat collimator with the Slit angle of 7 degree. While for gastric activity differentiation an angle of 15 degree for the Slit was useful.Conclusion: The results showed that Slit Slat collimation with 7 and 15 Slit angle provide a suitable differentiation of the bowel and gastric activities from the cardia, respectively.

In this study, a computer program is implemented to calculate the neutronic parameters of a multiplier system by Monte Carlo method. This program is able to perform the calculation of various parameters such as the effective multiplication factor, neutron flux distribution, and effective delayed neutrons of the system. This program calculates the prompt and the total multiplication factor of neutrons separately, then it can be used to calculate the effective fraction of delayed neutrons by the use of the eigenvalues and also the prompt method. The results obtained for the effective neutron multiplication factor and the neutron flux distribution are compared with the experimental measurements and the results of using MCNP4C code. In this approach a good agreement between them was obtained. The comparison between the obtained results for the effective fraction of delayed neutrons of the prompt method with those of the experimental measuremants and other applied methods showed that the prompt method is a suitable approach for the calculation of the effective fraction of delayed neutrons.