A Monte Carlo study on quantification of scattering and edge penetration in a breast-dedicated SPECT scanner with lofthole collimation

Document Type : Original Article


1 Department of Physics, Faculty of Science, University of Guilan, Rasht, Iran

2 Radiation Applications Research School, Nuclear Science and Technology Research Institute, Tehran, Iran


Introduction: Quantitative accuracy in SPECT is mainly affected by collimator penetration and scattering, particularly for high-energy imaging. Lofthole collimation offers superior performance in terms of penetration and scattering.
Methods: In this research, the GATE Monte Carlo simulator was exploited to calculate edge penetration and scattering in the lofthole collimator using an in-air and in-phantom point source of Tc-99m and I-123. The performance of the lofthole was then compared to that of a pinhole. Both lofthole and pinhole collimators were assumed to have the same geometry including an aperture diameter of 3.04 mm and an opening angle of 75°. Furthermore, the angular distribution of the scattering and penetration were investigated for a multi-lofthole collimator.
Results: The results show that penetration, scattering, and sensitivity are all a function of the photon energy. The penetration and scattering of the pinhole are about 4% higher than that of the lofthole collimator, for Tc-99m SPECT. Compared to the Tc-99m, I-123 SPECT suffers from approximately 1.5- and 1.42-fold higher penetration and scatter fractions, respectively, for lofthole aperture. Moreover, the lofthole collimator presents a higher sensitivity compared with the pinhole (0.030 versus 0.023 for the Tc-99m SPECT). In addition, the findings exhibit a reduction in sensitivity by increasing the photon incidence angle. Both scattering and penetration fractions illustrate a decreasing trend across the angle of incidence.
Conclusion: Compared to pinhole, the lofthole offers superior performance in terms of scattering and penetration for both low- and high-energy SPECT imaging.


Main Subjects

  1. Savelli G, Maffioli L, Maccauro M, De Deckere E, Bombardieri E. Bone scintigraphy and the added value of SPECT (single photon emission tomography) in detecting skeletal lesions. Q J Nucl Med. 2001 Mar;45(1):27-37.
  2. Brem RF, Rapelyea JA, Zisman G, Mohtashemi K, Raub J, Teal CB, Majewski S, Welch BL. Occult breast cancer: scintimammography with high-resolution breast-specific gamma camera in women at high risk for breast cancer. Radiology. 2005 Oct;237(1):274-80.
  3. Slomka PJ, Patton JA, Berman DS, Germano G. Advances in technical aspects of myocardial perfusion SPECT imaging. J Nucl Cardiol. 2009 Apr;16:255-76.
  4. Piruzan E, Vosoughi N, Mahdavi SR, Khalafi L, Mahani H. Target motion management in breast cancer radiation therapy. Radiol Oncol. 2021 Dec 1;55(4):393-408.
  5. Tarighati E, Keivan H, Mahani H. A review of prognostic and predictive biomarkers in breast cancer. Clin Exp Med. 2023 Feb;23(1):1-16.
  6. Van Audenhaege K, Van Holen R, Vandenberghe S, Vanhove C, Metzler SD, Moore SC. Review of SPECT collimator selection, optimization, and fabrication for clinical and preclinical imaging. Med Phys. 2015 Aug;42(8):4796-813.
  7. Mahani H, Raisali G, Kamali-Asl A, Ay MR. Spinning slithole collimation for high-sensitivity small animal SPECT: Design and assessment using GATE simulation. Phys Med. 2017 Aug;40:42-50.
  8. van der Have F, Ivashchenko O, Goorden MC, Ramakers RM, Beekman FJ. High-resolution clustered pinhole (131)Iodine SPECT imaging in mice. Nucl Med Biol. 2016 Aug;43(8):506-11.
  9. Deprez K, Pato LR, Vandenberghe S, Van Holen R. Characterization of a SPECT pinhole collimator for optimal detector usage (the lofthole). Phys Med Biol. 2013 Feb 21;58(4):859-85.
  10. Mahani H, Ay MR, Sarkar S, Farahani MH, inventors; Parto Negar Persia Co, assignee. Single photon emission computed tomography imaging with a spinning parallel-slat collimator. United States patent US 10,795,033. 2020 Oct 6.
  11. Mahani H, Raisali G, Kamali-Asl A, Ay MR. Collimator-detector response compensation in molecular SPECT reconstruction using STIR framework. Iran J Nucl Med. 2017;25(Supplement 1):26-34.
  12. Mahani H, Kamali-Asl A, Ay MR. How gamma camera’s head-tilts affect image quality of a nuclear scintigram?. Front biomed technol. 2014 Dec 30;1(4):265-70.
  13. Asma E, Manjeshwar R. Evaluation of the impact of resolution-sensitivity tradeoffs on detection performance for SPECT imaging. IEEE Nucl Sci Symp Conf Rec. 2008 Oct 19;  3730-3733
  14. Beekman FJ, Vastenhouw B. Design and simulation of a high-resolution stationary SPECT system for small animals. Phys Med Biol. 2004;49(19):4579.
  15. Wang H, Scarfone C, Greer KL, Coleman RE, Jaszczak RJ. Prone breast tumor imaging using vertical axis-of-rotation (VAOR) SPECT systems: an initial study. IEEE Trans Nucl Sci. 1997;44(3):1271-6.
  16. Weinmann AL, Hruska CB, O'Connor MK. Design of optimal collimation for dedicated molecular breast imaging systems. Med Phys. 2009 Mar;36(3):845-56.
  17. Williams MB, Judy PG, Gunn S, Majewski S. Dual-modality breast tomosynthesis. Radiology. 2010 Apr;255(1):191-8.
  18. Wang B, van Roosmalen J, Piët L, van Schie MA, Beekman FJ, Goorden MC. Voxelized ray-tracing simulation dedicated to multi-pinhole molecular breast tomosynthesis. Biomed Phys. Eng Express. 2017;3(4):045021.
  19. van Roosmalen J, Goorden MC, Beekman FJ. Molecular breast tomosynthesis with scanning focus multi-pinhole cameras. Phys Med Biol. 2016 Aug 7;61(15):5508-28.
  20. van Roosmalen J, Beekman FJ, Goorden MC. System geometry optimization for molecular breast tomosynthesis with focusing multi-pinhole collimators. Phys Med Biol. 2017 Dec 19;63(1):015018.
  21. Tornai MP, Bowsher JE, Archer CN, Peter J, Jaszczak RJ, MacDonald LR, Patt BE, Iwanczyk JS. A 3D gantry single photon emission tomograph with hemispherical coverage for dedicated breast imaging. Nucl Instrum Methods Phys Res Sect A Accel Spectrom Detect Assoc Equip. 2003;497(1):157-67.
  22. Saed M, Sadremomtaz A, Mahani H. Design and optimization of a breast-dedicated SPECT scanner with multi-lofthole collimation. J Instrum. 2022 Jan 4;17(01):P01006.
  23. van Holen R, Vandeghinste B, Deprez K, Vandenberghe S. Design and performance of a compact and stationary microSPECT system. Med Phys. 2013 Nov;40(11):112501.
  24. van der Have F, Vastenhouw B, Ramakers RM, Branderhorst W, Krah JO, Ji C, Staelens SG, Beekman FJ. U-SPECT-II: An ultra-high-resolution device for molecular small-animal imaging. J Nucl Med. 2009 Apr;50(4):599-605.
  25. Tornai MP, Bowsher JE, Jaszczak RJ, Pieper BC, Greer KL, Hardenbergh PH, Coleman RE. Mammotomography with pinhole incomplete circular orbit SPECT. J Nucl Med. 2003 Apr;44(4):583-93.
  26. Song TY, Choi Y, Chung YH, Jung JH, Choe YS, Lee KH, Kim SE, Kim BT. Optimization of pinhole collimator for small animal SPECT using Monte Carlo simulation. IEEE Trans Nucl Sci. 2003 Jun;50(3):327-32.
  27. Shokouhi S, Metzler SD, Wilson DW, Peterson TE. Multi-pinhole collimator design for small-object imaging with SiliSPECT: a high-resolution SPECT. Phys Med Biol. 2009 Jan 21;54(2):207-25.
  28. Paix D. Pinhole imaging of gamma rays. Phys Med Biol. 1967 Oct;12(4):489-500.
  29. Könik A, Auer B, De Beenhouwer J, Kalluri K, Zeraatkar N, Furenlid LR, King MA. Primary, scatter, and penetration characterizations of parallel-hole and pinhole collimators for I-123 SPECT. Phys Med Biol. 2019 Dec 13;64(24):245001.
  30. Shafaei M, Ay MR, Sardari D, Dehestani N, Zaidi H. Monte Carlo assessment of geometric, scatter and septal penetration components in DST-XLi HEGP collimator. 4th European Conference of the International Federation for Medical and Biological Engineering: ECIFMBE 2008 23–27. November 2008 Antwerp, Belgium 2009: 2479-2482. Springer Berlin Heidelberg.
  31. van Der Have F, Beekman FJ. Penetration, scatter and sensitivity in channel micro-pinholes for SPECT: a Monte Carlo investigation. IEEE Trans Nucl Sci. 2006;53(5):2635-45.
  32. Nguyen MP, Goorden MC, Beekman FJ. EXIRAD-HE: multi-pinhole high-resolution ex vivo imaging of high-energy isotopes. Phys Med Biol. 2020 Nov 18;65(22):225029.
  33. Cot A, Sempau J, Pareto D, Bullich S, Pavia J, Calvino F. Evaluation of the geometric, scatter, and septal penetration components in fan-beam collimators using Monte Carlo simulation. IEEE Trans Nucl Sci. 2002;49(1):12-6.
  34. Dewaraja YK, Ljungberg M, Koral KF. Characterization of scatter and penetration using Monte Carlo simulation in 131I imaging. J Nucl Med. 2000 Jan;41(1):123-30
  35. Zaidi H. Relevance of accurate Monte Carlo modeling in nuclear medical imaging. Med Phys. 1999 Apr;26(4):574-608.
  36. Staelens S, Buvat I. Chapter 5 - Monte Carlo Simulations in nuclear medicine imaging. Verdonck P, editor. Advances in biomedical engineering. Amsterdam: Elsevier; 2009. p. 177-209.
  37. Briesmeister JF. MCNPTM-A general Monte Carlo N-particle transport code. Version 4C, LA-13709-M, Los Alamos National Laboratory. 2000; 2.
  38. GEANT4. Available from: https://geant4.web.cern.ch/.
  39. Jan S, Santin G, Strul D, Staelens S, Assié K, Autret D, Avner S, Barbier R, Bardies M, Bloomfield PM, Brasse D. GATE: a simulation toolkit for PET and SPECT. Physics in medicine and biology. 2004 Sep 10;49(19):4543.
  40. OpenGATE Collaboration. Updated on July 01, 2021. Available from: http://www.opengatecollaboration.org/.
  41. Mahani H, Raisali G, Kamali-Asl A, Ay MR. How crystal configuration affects the position detection accuracy in pixelated molecular SPECT imaging systems?. Nucl Sci Tech. 2017 Apr;28:1-7.
  42. Piruzan E, Vosoughi N, Mahani H. Development and validation of an optimal GATE model for double scattering proton beam delivery. J Instrum. 2021 Feb 18;16(02):P02022.
  43. Cherry SR, Sorenson JA, Phelps ME. Physics in Nuclear Medicine. 4th Ed. Philadelphia: Elsevier Inc.; 2012.
  44. Knoll GF. Radiation detection and measurement. John Wiley & Sons; 2010.
  45. Framework RDA. ROOT Data Analysis Framework. Available from: https://root.cern/.
  46. Metzler SD, Bowsher JE, Smith MF, Jaszczak RJ. Analytic determination of pinhole collimator sensitivity with penetration. IEEE Trans Med Imaging. 2001 Aug;20(8):730-41
  47. Deloar HM, Watabe H, Aoi T, Iida H. Evaluation of penetration and scattering components in conventional pinhole SPECT: phantom studies using Monte Carlo simulation. Phys Med Biol. 2003 Apr 21;48(8):995-1008.
  48. Jung YJ, Kim K, Kim J, Woo SK, Park J, Lee YS, Lee W, Yu JW, Lee K, Kim J. Modeling high energy (I-131) pinhole collimator for small animal gamma ray imaging device by Monte Carlo simulation (GATE 6.0). 2011 IEEE Nucl Sci Conf R. 2011 Oct 23; 2756-2759.