METHODS: Multiple time-point whole-body planar images and one SPECT/CT image were acquired from 18 patients including 177Lu-PSMA I&T (13 patients) and 177Lu-DOTATATE treatment (5 patients) after administration of 3.80-8.58 GBq injected activity. The regions of interest were drawn in the whole body, kidneys, liver, urinary bladder, salivary glands, and tumors to determine the time-integrated activity (TIA) in source organs. Absorbed doses in target organs were calculated according to the Medical Internal Radiation Dose (MIRD) scheme using the HERMES HybridViewer dosimetry integrated with OLINDA/EXM V.2.1 that utilizes the non-uniform rational B-splines (NURBS) for computational digital phantom.
RESULTS: The planar-based dosimetry showed a higher dose per injected activity compared to the hybrid-based dosimetry, primarily due to organ overlap. The highest difference in absorbed dose between the imaging scenarios was observed in the spleen with a variation of up to 51.6%, while the difference for other target organs and tumors was less than 40%.
CONCLUSIONS: The dosimetry calculation derived from the 2D planar-based method consistently demonstrates a significantly higher absorbed dose in organs and tumors compared with the hybrid-based method. However, the hybrid method outperforms the planar method in terms of tumor visualization and overlap-free organ delineation.
方法:从18例患者中获取了多个时间点全身平面图像和一个SPECT/CT图像,包括177Lu-PSMAI&T(13例)和177Lu-DOTATATE治疗(5例)。注射3.80-8.58GBq的活动。感兴趣的区域被绘制在整个身体中,肾脏,肝脏,膀胱,唾液腺,和肿瘤来确定源器官的时间整合活性(TIA)。根据医学内部辐射剂量(MIRD)方案,使用与OLINDA/EXMV.2.1集成的HERMESHybridViewer剂量测定法计算靶器官的吸收剂量,该剂量利用非均匀有理B样条(NURBS)进行计算数字体模。
结果:与基于混合的剂量测定法相比,基于平面的剂量测定法显示每次注射活动的剂量更高,主要是由于器官重叠。在脾脏中观察到成像方案之间吸收剂量的最高差异,变化高达51.6%,而其他靶器官和肿瘤的差异小于40%。
结论:基于2D平面的方法得出的剂量测定计算始终表明,与基于混合的方法相比,器官和肿瘤的吸收剂量明显更高。然而,在肿瘤可视化和无重叠器官勾画方面,混合方法优于平面方法。