背景:我们研究的目的是比较从PET/MRI和PET/CT治疗后成像获得的90Y剂量学在原发性或转移性肝肿瘤患者中的应用。首先,在PET/CT和PET/MRI系统上都获得了一个充满水的Jaszczak体模,其中包含90Y氯化物的可填充球体,以检查模式的交叉校准。使用90Y微球进行选择性内部放射治疗(SIRT)后,32例患者在PET/CT系统上成像,立即进行PET/MRI研究。将重建的图像转移到公共平台并用于计算90Y剂量测定。使用Passing-Bablok回归散点图和Bland和Altman方法分析了剂量测定值之间的差异。
结果:体模研究表明,两种模式的校准误差均小于1%。根据PET/CT和PET/MRI计算的32名受试者的平均肝脏剂量分别为51.6±24.7Gy和46.5±22.7Gy,分别,平均差为5.1±5.0Gy。重复性系数为9.0(平均值的18.5%)。Spearman等级相关系数很高,ρ=0.97。尽管肝脏的最大剂量可能会有很大差异(高达40%),每种模式的平均肝脏剂量相对接近,相差18.5%或更小。
结论:使用PET/CT与PET/MRI的90Y剂量学计算差异的两个主要原因可以归因于感兴趣区域(ROI)的差异和归因于衰减校正的差异。由于MRI的优越的软组织对比度,肝脏轮廓通常比CT图像更好。然而,PET/CT可以更好地量化PET图像,由于更好的衰减校正。尽管存在这些差异,我们的结果表明,治疗后90Y研究中PET/MRI和PET/CT的剂量学值相似.
BACKGROUND: The aim of our study was to compare 90Y dosimetry obtained from PET/MRI versus PET/CT post-therapy imaging among patients with primary or metastatic hepatic tumors. First, a water-filled Jaszczak phantom containing fillable sphere with 90Y-chloride was acquired on both the PET/CT and PET/MRI systems, in order to check the cross-calibration of the modalities. Following selective internal radiation therapy (SIRT) with 90Y microspheres, 32 patients were imaged on a PET/CT system, immediately followed by a PET/MRI study. Reconstructed images were transferred to a common platform and used to calculate 90Y dosimetry. A Passing-Bablok regression scatter diagram and the Bland and Altman method were used to analyze the difference between the dosimetry values.
RESULTS: The phantom study showed that both modalities were calibrated with less than 1% error. The mean liver doses for the 32 subjects calculated from PET/CT and PET/MRI were 51.6 ± 24.7 Gy and 46.5 ± 22.7 Gy, respectively, with a mean difference of 5.1 ± 5.0 Gy. The repeatability coefficient was 9.0 (18.5% of the mean). The Spearman rank correlation coefficient was very high, ρ = 0.97. Although the maximum dose to the liver can be significantly different (up to 40%), mean liver doses from each modalities were relatively close, with a difference of 18.5% or less.
CONCLUSIONS: The two main contributors to the difference in 90Y dosimetry calculations using PET/CT versus PET/MRI can be attributed to the differences in regions of interest (ROIs) and differences attributed to attenuation correction. Due to the superior soft-tissue contrast of MRI, liver contours are usually better seen than in CT images. However, PET/CT provides better quantification of PET images, due to better attenuation correction. In spite of these differences, our results demonstrate that the dosimetry values obtained from PET/MRI and PET/CT in post-therapy 90Y studies were similar.