Optimization of Energy Window and Collimator for Y-90 Bremsstrahlung SPECT imaging: A Monte Carlo Simulation Study

Document Type : Original Paper


1 Department of Physics, LPHE, Modeling and Simulations, Faculty of Science, Mohammed V University, Rabat, Morocco

2 Department of Physics,LPHE, Modeling and Simulations, Faculty of Science, Mohammed V University, Rabat, Morocco

3 Academic Hospital of Udine, Department of Medical Physics, Udine, Italy

4 Department of Physics,LPHE, Modeling and Simulations, Faculty of Science,Mohammed V University, Rabat, Morocco


Introduction: In yttrium-90 imaging, image quality is highly dependent on the selection of energy window and collimator design becausetheY-90 bremsstrahlung photons have a continuous and broad energy distribution. The current study aimed to optimize the bremsstrahlung energy window setting and collimator for the improvement of both resolution and sensitivity.
Material and Methods: In the present study, simulation of medical imaging nuclear detectors (SIMIND) Monte Carlo program was used to simulate Siemens Medical System Symbia. The SIMIND was utilized to generate the Y-90 bremsstrahlung single-photon emission computed tomography (SPECT) projection of the point source. Six energy windows settings and two collimators denoting medium energy and high energy were used in order to assess the effect of the energy window on the resolution.
Results: The experimental measurements and simulation results showed a similar pattern in the point spread functions with the energy window. The simulation data indicated that the geometric component reached 73%for the energy window within the range of51-120keVusingthe high-energy (HE) collimator. In addition, the obtained results showed that the full width at half maximum (FWHM) and full width at tenth maximum (FWTM)(FWHM=7mm and FWTM=35mm)were higher in this window in comparison to those reported for other windows.
Conclusion: According to the obtained results of the present study, the optimal energy window for Y-90 bremsstrahlung SPECT imaging was within the range of 51-120 keV. The obtained optimal energy window and optimal HE collimator had the potential to improve the image resolution and sensitivity of Y-90 SPECT images


Main Subjects


    1. Stigbrand T, Carlsson J, Adams GP, editors. Targeted radionuclide tumor therapy: Biological aspects. New York: Springer; 2008 Sep 1.
    2. Nag S, Kennedy A, Salem R, Murthy R, McEwan A, Nutting C, et al. Recommendations for radioembolization of hepatic malignancies using Yttrium-90 microsphere brachytherapy: A consensus panel report from the Radioembolization Brachytherapy Oncology Consortium (REBOC). Brachytherapy. 2007 Apr 1;6(2):116-7.
    3. Rong X, Frey EC. A collimator optimization method for quantitative imaging: Application to Y‐90 bremsstrahlung SPECT. Medical physics. 2013 Aug;40(8):082504.
    4. Rong X, Ghaly M, Frey EC. Optimization of energy window for 90Y bremsstrahlung SPECT imaging for detection tasks using the ideal observer with model‐mismatch. Medical physics. 2013 Jun;40(6Part1):062502.
    5. Rong X, Du Y, Frey EC. A method for energy window optimization for quantitative tasks that includes the effects of model-mismatch on bias: application to Y-90 bremsstrahlung SPECT imaging. Physics in Medicine & Biology. 2012 May 23;57(12):3711.
    6. Heard S, Flux GD, Guy MJ, Ott RJ. Photon source kernels for Monte Carlo simulation of bremsstrahlung imaging. Ineuropean journal of nuclear medicine and molecular imaging. 2004 Aug 1; 31:403.
    7. Shen S, Denardo G, Yuan A, Denardo D and Denardo S. Planar gamma-camera imaging and quantitation of Y-90 bremsstrahlung. J. Nucl. Med. 1994;35:1381–9.
    8. Yue J, Mauxion T, Reyes DK, Lodge MA, Hobbs RF, et al. Comparison of quantitative Y-90 SPECT and non-time-of-flight PET imaging in post-therapy radio embolization of liver cancer. Med Phys. 2016 Oct;43(10):5779.
    9. Elschot M, Vermolen B, Lam M, de Keizer B, van den Bosch M, de Jong H. Quantitative comparison of PET and SPECT for imaging the yttrium-90 microsphere distribution after liver radio embolization. Journal of Nuclear Medicine. 2012 May 1;53(supplement 1):103.
    10. Bouzekraoui Y, Bentayeb F, Asmi H, Bonutti F. Energy window and contrast optimization for single-photon emission computed tomography bremsstrahlung imaging with yttrium-90. Indian journal of nuclear medicine: IJNM: the official journal of the Society of Nuclear Medicine, India. 2019 Apr;34(2):125.
    11. De Vries DJ, Moore SC. Approximation of hexagonal holes by square holes in Monte Carlo simulation of gamma-camera collimation. IEEE Transactions on Nuclear Science. 2002 Dec 10;49(5):2186-95.
    12. Ljungberg M. The SIMIND Monte Carlo program home page. 2018. Available from:  https://www.msf.lu.se/research/the-simind-monte-carlo-program.
    13. Ferreira T.Rasband W. Image J Program. 2018. Availablefrom:https://imagej.nih.gov/ij/download.html.