碘-123和碘-131单光子发射计算机断层扫描活性定量评估：一项蒙特卡洛研究。
Evaluation of Iodine-123 and Iodine-131 SPECT activity quantification: a Monte Carlo study.
作者信息
Morphis Michaella, van Staden Johan A, du Raan Hanlie, Ljungberg Michael
机构信息
Department of Medical Physics, Faculty of Health Sciences, University of the Free State, PO Box 339, Bloemfontein, 9300, South Africa.
Medical Radiation Physics, Lund University, Lund, Sweden.
出版信息
EJNMMI Phys. 2021 Aug 19;8(1):61. doi: 10.1186/s40658-021-00407-1.
PURPOSE
The quantitative accuracy of Nuclear Medicine images, acquired for both planar and SPECT studies, is influenced by the isotope-collimator combination as well as image corrections incorporated in the iterative reconstruction process. These factors can be investigated and optimised using Monte Carlo simulations. This study aimed to evaluate SPECT quantification accuracy for I with both the low-energy high resolution (LEHR) and medium-energy (ME) collimators and I with the high-energy (HE) collimator.
METHODS
Simulated SPECT projection images were reconstructed using the OS-EM iterative algorithm, which was optimised for the number of updates, with appropriate corrections for scatter, attenuation and collimator detector response (CDR), including septal scatter and penetration compensation. An appropriate calibration factor (CF) was determined from four different source geometries (activity-filled: water-filled cylindrical phantom, sphere in water-filled (cold) cylindrical phantom, sphere in air and point-like source), investigated with different volume of interest (VOI) diameters. Recovery curves were constructed from recovery coefficients to correct for partial volume effects (PVEs). The quantitative method was evaluated for spheres in voxel-based digital cylindrical and patient phantoms.
RESULTS
The optimal number of OS-EM updates was 60 for all isotope-collimator combinations. The CF with a VOI diameter equal to the physical size plus a 3.0-cm margin was selected, for all isotope-collimator geometries. The spheres' quantification errors in the voxel-based digital cylindrical and patient phantoms were less than 3.2% and 5.4%, respectively, for all isotope-collimator combinations.
CONCLUSION
The study showed that quantification errors of less than 6.0% could be attained, for all isotope-collimator combinations, if corrections for; scatter, attenuation, CDR (including septal scatter and penetration) and PVEs are performed. I LEHR and I ME quantification accuracies compared well when appropriate corrections for septal scatter and penetration were applied. This can be useful in departments that perform I studies and may not have access to ME collimators.
目的
用于平面和单光子发射计算机断层显像（SPECT）研究的核医学图像的定量准确性受同位素 - 准直器组合以及迭代重建过程中纳入的图像校正影响。这些因素可通过蒙特卡罗模拟进行研究和优化。本研究旨在评估使用低能高分辨率（LEHR）准直器和中能（ME）准直器对碘（I）以及使用高能（HE）准直器对另一种碘（I）进行SPECT定量的准确性。
方法
使用有序子集期望最大化（OS - EM）迭代算法重建模拟的SPECT投影图像，该算法针对更新次数进行了优化，并对散射、衰减和准直器探测器响应（CDR）进行了适当校正，包括隔板散射和穿透补偿。从四种不同的源几何形状（活性填充：水填充圆柱形体模、水填充（冷）圆柱形体模中的球体、空气中的球体和点状源）确定合适的校准因子（CF），并使用不同的感兴趣体积（VOI）直径进行研究。根据恢复系数构建恢复曲线以校正部分容积效应（PVE）。在基于体素的数字圆柱形和患者体模中对球体的定量方法进行评估。
结果
对于所有同位素 - 准直器组合，OS - EM更新的最佳次数为60次。对于所有同位素 - 准直器几何形状，选择VOI直径等于物理尺寸加上3.0厘米余量的CF。对于所有同位素 - 准直器组合，基于体素的数字圆柱形体模和患者体模中球体量化误差分别小于3.2%和5.4%。
结论
该研究表明，如果对散射、衰减、CDR（包括隔板散射和穿透）和PVE进行校正，对于所有同位素 - 准直器组合可实现小于6.0%的量化误差。当对隔板散射和穿透进行适当校正时，碘 - 123（I - 123）低能高分辨率（LEHR）和碘 - 123中能（I - 123 ME）定量准确性相当。这对于进行碘 - 123研究且可能无法使用中能准直器的科室可能有用。
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