Vergnaud Laure, Robert Antoine, Baudier Thomas, Parisse-Di Martino Sandrine, Boissard Philippe, Rit Simon, Badel Jean-Noël, Sarrut David
CREATIS; CNRS UMR 5220; INSERM U 1044; Université de Lyon; INSA-Lyon, Université Lyon 1, Lyon, France.
Centre de Lutte Contre Le Cancer Léon Bérard, Lyon, France.
EJNMMI Phys. 2023 Feb 7;10(1):8. doi: 10.1186/s40658-023-00525-y.
In selective internal radiation therapy, Tc SPECT images are used to optimize patient treatment planning, but they are affected by respiratory motion. In this study, we evaluated on patient data the dosimetric impact of motion-compensated SPECT reconstruction on several volumes of interest (VOI), on the tumor-to-normal liver (TN) ratio and on the activity to be injected.
Twenty-nine patients with liver cancer or hepatic metastases treated by radioembolization were included in this study. The biodistribution of Y is assumed to be the same as that of Tc when predictive dosimetry is implemented. A total of 31 Tc SPECT images were acquired and reconstructed with two methods: conventional OSEM (3D) and motion-compensated OSEM (3Dcomp). Seven VOI (liver, lungs, tumors, perfused liver, hepatic reserve, healthy perfused liver and healthy liver) were delineated on the CT or obtained by thresholding SPECT images followed by Boolean operations. Absorbed doses were calculated for each reconstruction using Monte Carlo simulations. Percentages of dose difference (PDD) between 3Dcomp and 3D reconstructions were estimated as well as the relative differences for TN ratio and activities to be injected. The amplitude of movement was determined with local rigid registration of the liver between the 3Dcomp reconstructions of the extreme phases of breathing.
The mean amplitude of the liver was 9.5 ± 2.7 mm. Medians of PDD were closed to zero for all VOI except for lungs (6.4%) which means that the motion compensation overestimates the absorbed dose to the lungs compared to the 3D reconstruction. The smallest lesions had higher PDD than the largest ones. Between 3D and 3Dcomp reconstructions, means of differences in lung dose and TN ratio were not statistically significant, but in some cases these differences exceed 1 Gy (4/31) and 8% (2/31). The absolute differences in activity were on average 3.1% ± 5.1% and can reach 22.8%.
The correction of respiratory motion mainly impacts the lung and tumor doses but only for some patients. The largest dose differences are observed for the smallest lesions.
在选择性内放射治疗中，锝单光子发射计算机断层扫描（Tc SPECT）图像用于优化患者治疗计划，但会受到呼吸运动的影响。在本研究中，我们基于患者数据评估了运动补偿SPECT重建对多个感兴趣区（VOI）、肿瘤与正常肝脏（TN）比值以及待注射活度的剂量学影响。
本研究纳入了29例接受放射性栓塞治疗的肝癌或肝转移患者。在实施预测剂量测定时，假设钇的生物分布与锝相同。共采集了31幅Tc SPECT图像，并采用两种方法进行重建：传统的有序子集期望最大化（OSEM）（3D）和运动补偿OSEM（3Dcomp）。在CT上勾勒出7个VOI（肝脏、肺、肿瘤、灌注肝、肝储备、健康灌注肝和健康肝脏），或通过对SPECT图像进行阈值处理并随后进行布尔运算获得。使用蒙特卡罗模拟计算每种重建的吸收剂量。估计了3Dcomp和3D重建之间的剂量差异百分比（PDD）以及TN比值和待注射活度的相对差异。通过对呼吸极端相位的3Dcomp重建之间的肝脏进行局部刚性配准来确定运动幅度。
肝脏的平均运动幅度为9.5±2.7毫米。除肺（6.4%）外，所有VOI的PDD中位数均接近于零，这意味着与3D重建相比，运动补偿高估了肺的吸收剂量。最小的病变比最大的病变具有更高的PDD。在3D和3Dcomp重建之间，肺剂量和TN比值的差异均值无统计学意义，但在某些情况下，这些差异超过1 Gy（4/31）和8%（2/31）。活度的绝对差异平均为3.1%±5.1%，可达22.8%。
呼吸运动校正主要影响肺和肿瘤剂量，但仅对部分患者有影响。最小的病变观察到最大的剂量差异。
