عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Performance of parallel-hole collimators may be evaluated by determining their response to a point radioactive source which for instance, the amount of collimator resolution is calculated by measuring the full width at half maximum (FWHM) of point spread function (PSF). The conventional method in calculating the response of the collimator to a point source by using Monte Carlo simulations is to map the signal values in each detector cell to the center of cell on the x or y axis. In this paper, a new computing algorithm has been proposed which optimally maps the signal values on these axes. The responses of LEUHR, LEHR, LEGP and LEHS collimators are simulated based on the conventional method and the optimized computing one by the MCNP5 code. The results have been indicated that the response based on the optimized method has a higher accuracy compared to that of the conventional one. The average relative differences between the amounts of resolution based on the optimized method and experimental data have been found to be considerably fewer than those of the conventional one. Therefore, one may obtain parallel hole collimators’ response with a higher accuracy by using the optimized computing method.
 J.T. Bush Berg, J.A. Seibert, E.M. Leidholdt, J.M. Boone, The essential physics of medical imaging, Lippincott Williams & wilkins Press, 3th Edition, (2012).
 E. Asma, R. Manjeshwar, Evaluation of the impact of resolution-sensitivity tradeoffs on detection performance for SPECT imaging 2008 IEEE. Nucl. Sci. Symp., (2008) 3730-33.
 G. Trinci, R. Massari, M. Scandellari, S. Boccalini, A. Costantini, R. DiSero, A. Basso, R. Sala, F. Scopinaro, A. Soluri, A new variable parallel holes collimator for scintigraphic device with validation method based on Monte Carlo simulations, Nucl. Instrum. Methods, A621 (2010) 406-412.
 S. Mahmood, K. Erlandsson, I. Cullum, B. Hutton,Design of a novel slit-slat collimator system for SPECT imaging of the human brain Phys. Med. Biol, 54 (2009) 3433-3450.
 S.D. Metzler, R. Accorsi, S. Ayan, R.J. Jaszczak, Slit-slat and multi slit-slat collimator design and experimentally acquired phantom images from a rotating prototype, IEEE Trans. Nucl. Sci., 57 (2010) 125-134.
 A. Khorshidi, M. Ashoor, Modulation transfer function assessment in parallel and fan beam collimator with square and cylindrical holes, Ann. Nucl. Med., 28 (2014) 59-66.
 A. Khorshidi, M. Ashoor, S.H. Hosseini, A. Rajaee, Evaluation of collimators' response: Round and hexagonal holes in parallel and fan beam, Progress in Biophysics and Molecular Biology, 109 (2012) 59-66.
 T. Yong Song, Y. Choi, Y.H. Chung, J.H. Jung, Y. Seong Choe, K. Han Lee, S. Eun Kim, B. Tae Kim, Optimization of pinhole collimator for small animal SPECT using Monte Carlo simulation IEEE Trans. Nucl. Sci., 50 (2003) 327-332.
 D. Lowe, A. Truman, H. Kwok, A. Bergman, Optimisation of the design of round-hole parallel collimators for ultra-compact nuclear medicine imaging, Nucl. Instrum. Methods, A., 621 (2002) 406-412.
 V. Moslemi, M. Ashoor, Design and performance evaluation of a new high energy parallel hole collimator for radioiodine planar imaging by gamma cameras: Monte Carlo simulation study, Ann. Nucl. Med., (2017) DOI:10.1007/s 12149-017-1160-9.
 B. Zhang, G.L. Zeng, High-resolution versus high-sensitivity SPECT imaging with geometric blurring compensation for various parallel-hole collimation geometries, IEEE Trans. Inf. Technol. Biomed., 14 (2010) 1121-7.
 C.E. Metz, F.B. Atkins, R.N. Beck, The geometric transfer function component for scintillation camera collimators with straight parallel holes, Phys. Med. Biol., 25 6 (1980) 242–250.
 H. Zaidi, E.C. Frey, B.M.W. Tsui, Collimator-detector response compensation in SPECT, Quantitative Analysis in Nuclear Medicine Imaging, Springer, (2006) 141–166.
 S. Liu, T.H. Farncombe, Collimator-detector response compensation in quantitative SPECT reconstruction, IEEE. Nucl. Sci. Symp. Conf., 5 (2007) 3955-60.
 K. Assie, I. Gardin, P. Vera, I. Buvat, Validation of the Monte Carlo simulator GATE for Indium-111 imaging. Phys. Med. Biol., 50 (2005) 3113-25.
 A. Cot, E. Jane, J. Sempau, C. Falcon, S. Bullich, J. Pavia, F. Calvino, D. Ros, Modeling of high-energy contamination in SPECT imaging using Monte Carlo simulation, IEEE Trans. Nucl. Sci., 53, 1 (2006) 198–203.
 S. Staelens, T. Wit, F. Beekman, Fast hybrid SPECT simulation including efficient septal penetration modeling (SP-PSF), Phys. Med. Biol., 52 11 (2007) 3027–43.
 X. Song, W.P. Segars, Y. Du, B.M.W. Tsui, E.C. Frey, Fast modeling of the collimator-detector response in Monte Carlo simulation of SPECT imaging using the angular response function. Phys. Med. Biol., 50 8 (2005) 1791–1804.
 E. Rault, S. Staelens, R.V. Holen, J.D. Beenhouwer, S. Vandenberghe, Fast simulation of yttrium-90 bremsstrahlung photons with GATE, Med. Phys., 37 6 (2010) 2943–50.
 J.F. Knoll, Radiation detection and measurement, John Wiley & Sons Press, 4th Edition (2010).