背景:先前的放射栓塞,使用99mTc-宏聚集白蛋白作为90Y-微球替代进行模拟。伽玛闪烁显像图像(平面,SPECT,或SPECT-CT)可评估肝内90Y微球的分布并检测可能的肝外和肺分流。这些图像可以用于治疗前剂量测定评估,以计算在保留健康组织的同时获得最佳肿瘤反应的90Y活性。有几种剂量测定方法可用,但对于计算吸收剂量的最佳方法仍未达成共识。这项研究的目的是回顾性评估使用不同剂量学方法对基于99mTc-MAA图像的90Y放射性栓塞治疗前吸收剂量评估的影响。
方法:评价了由分区模型(PM)和3D体素剂量测定法(3D-VDM)(剂量点核卷积和局部沉积法)产生的感兴趣体积内的吸收剂量。此外,开发了一种新的“多肿瘤分区模型”(MTPM)。根据平均吸收剂量和目标体积内的剂量体积直方图评估剂量测定方法之间的差异。
结果:剂量学方法中平均吸收剂量的差异在肿瘤体积中高于在非肿瘤体积中的差异。MTPM和两个3D-VDM之间的差异明显低于PM和任何3D-VDM之间观察到的差异。PM与其他研究的剂量学方法之间的相关性和一致性较差。从任一3D-VDM获得的DVH在健康肝脏和个体肿瘤中非常相似。虽然没有相关的全球差异,以Gy为单位的吸收剂量,在两个3D-VDM之间找到了,已观察到重要的逐个体素差异。
结论:所研究的90Y放射栓塞治疗剂量学方法之间存在显着差异。差异不会对健康组织的治疗计划产生实质性影响,但对肿瘤肝产生影响。肿瘤的个体分割和评估是必不可少的。在多发性肿瘤患者中,PM的应用不是最佳的,而是建议3D-VDM或新的MTPM。如果3D-VDM方法不可用,MTPM是最好的选择。此外,两种3D-VDM方法都可以不明确地使用。
BACKGROUND: Prior radioembolization, a simulation using 99mTc-macroaggregated albumin as 90Y-microspheres surrogate is performed. Gamma scintigraphy images (planar, SPECT, or SPECT-CT) are acquired to evaluate intrahepatic 90Y-microspheres distribution and detect possible extrahepatic and lung shunting. These images may be used for pre-treatment dosimetry evaluation to calculate the 90Y activity that would get an optimal tumor response while sparing healthy tissues. Several dosimetry methods are available, but there is still no consensus on the best methodology to calculate absorbed doses. The goal of this study was to retrospectively evaluate the impact of using different dosimetry approaches on the resulting 90Y-radioembolization pre-treatment absorbed dose evaluation based on 99mTc-MAA images.
METHODS: Absorbed doses within volumes of interest resulting from partition model (PM) and 3D voxel dosimetry methods (3D-VDM) (dose-point kernel convolution and local deposition method) were evaluated. Additionally, a new \"Multi-tumor Partition Model\" (MTPM) was developed. The differences among dosimetry approaches were evaluated in terms of mean absorbed dose and dose volume histograms within the volumes of interest.
RESULTS: Differences in mean absorbed dose among dosimetry methods are higher in tumor volumes than in non-tumoral ones. The differences between MTPM and both 3D-VDM were substantially lower than those observed between PM and any 3D-VDM. A poor correlation and concordance were found between PM and the other studied dosimetry approaches. DVH obtained from either 3D-VDM are pretty similar in both healthy liver and individual tumors. Although no relevant global differences, in terms of absorbed dose in Gy, between both 3D-VDM were found, important voxel-by-voxel differences have been observed.
CONCLUSIONS: Significant differences among the studied dosimetry approaches for 90Y-radioembolization treatments exist. Differences do not yield a substantial impact in treatment planning for healthy tissue but they do for tumoral liver. An individual segmentation and evaluation of the tumors is essential. In patients with multiple tumors, the application of PM is not optimal and the 3D-VDM or the new MTPM are suggested instead. If a 3D-VDM method is not available, MTPM is the best option. Furthermore, both 3D-VDM approaches may be indistinctly used.