Morphis Michaella, van Staden Johan A, du Raan Hanlie, Ljungberg Michael
Department of Medical Physics, Faculty of Health Sciences, University of the Free State, Bloemfontein, South Africa.
Department of Medical Radiation Physics, Lund University, Lund, Sweden.
Heliyon. 2021 Feb 10;7(2):e06097. doi: 10.1016/j.heliyon.2021.e06097. eCollection 2021 Feb.
Monte Carlo (MC) modelling techniques have been used extensively in Nuclear Medicine (NM). The theoretical energy resolution relationship ( ), does not accurately predict the gamma camera detector response across all energies. This study aimed to validate the accuracy of an energy resolution model for the SIMIND MC simulation code emulating the Siemens Symbia T16 dual-head gamma camera.
Measured intrinsic energy resolution data (full width half maximum (FWHM) values), for Ba-133, Lu-177, Am-241, Ga-67, Tc-99m, I-123, I-131 and F-18 sources in air, were used to create a of the energy response of the gamma camera. Both the and were used to simulate intrinsic and extrinsic energy spectra using three different scenarios (source in air; source in simple scatter phantom and a clinical voxel-based digital patient phantom).
The results showed the underestimated the FWHM values at energies above 160.0 keV up to 23.5 keV. In contrast, the better predicted the measured FWHM values with differences less than 3.3 keV. The I-131 in-scatter energy spectrum simulated with the better matched the measured energy spectrum. Higher energy photopeaks, (I-123: 528.9 keV and I-131: 636.9 keV) simulated with the , more accurately resembled the measured photopeaks. The voxel-based digital patient phantom energy spectra, simulated with the and models, showed the potential impact of an incorrect energy resolution model when simulating isotopes with multiple photopeaks.
Modelling of energy resolution with the proposed enables the SIMIND user to accurately simulate NM images. A great improvement was seen for high-energy photon emitting isotopes (e.g. I-131), as well as isotopes with multiple photopeaks (e.g. Lu-177, I-131 and Ga-67) in comparison to the . This will result in accurate evaluation of radioactivity quantification, which is vital for dosimetric purposes.
蒙特卡罗（MC）建模技术已在核医学（NM）中广泛应用。理论能量分辨率关系（ ）并不能准确预测γ相机探测器在所有能量下的响应。本研究旨在验证用于模拟西门子Symbia T16双头γ相机的SIMIND MC模拟代码的能量分辨率模型的准确性。
使用在空气中测量的Ba-133、Lu-177、Am-241、Ga-67、Tc-99m、I-123、I-131和F-18源的固有能量分辨率数据（半高宽（FWHM）值），来创建γ相机能量响应的（ ）。（ ）和（ ）都用于使用三种不同场景（空气中的源；简单散射体模中的源和基于体素的临床数字患者体模）模拟固有和外在能谱。
结果表明，（ ）在能量高于160.0 keV至23.5 keV时低估了FWHM值。相比之下，（ ）能更好地预测测量的FWHM值，差异小于3.3 keV。用（ ）模拟的I-131散射能谱与测量能谱更匹配。用（ ）模拟的较高能量光电峰（I-123：528.9 keV和I-131：636.9 keV）更准确地类似于测量的光电峰。用（ ）和（ ）模型模拟的基于体素的数字患者体模能谱，显示了在模拟具有多个光电峰的同位素时，不正确的能量分辨率模型的潜在影响。
使用所提出的（ ）对能量分辨率进行建模，使SIMIND用户能够准确模拟核医学图像。与（ ）相比，对于发射高能光子的同位素（例如I-131）以及具有多个光电峰的同位素（例如Lu-177、I-131和Ga-67）有了很大改进。这将导致对放射性定量的准确评估，这对于剂量学目的至关重要。
