Department of Radiation Oncology and Proton Medical Research Center, Faculty of Medicine, University of Tsukuba, 2-1-1 Amakubo, Tsukuba, Ibaraki, 305-8576, Japan.
Department of Radiation Oncology, Kobe Proton Center, 1-6-8, Minatoshima-Minamimachi, Kobe, 650-0047, Japan.
Ann Nucl Med. 2024 Apr;38(4):305-314. doi: 10.1007/s12149-024-01901-z. Epub 2024 Feb 14.
To investigate differences in uptake regions between methyl-C-L-methionine positron emission tomography (C-MET PET) and gadolinium (Gd)-enhanced magnetic resonance imaging (MRI), and their impact on dose distribution, including changing of the threshold for tumor boundaries.
Twenty consecutive patients with grade 3 or 4 glioma who had recurrence after postoperative radiotherapy (RT) between April 2016 and October 2017 were examined. The study was performed using simulation with the assumption that all patients received RT. The clinical target volume (CTV) was contoured using the Gd-enhanced region (CTV(Gd)), the tumor/normal tissue (T/N) ratios of C-MET PET of 1.3 and 2.0 (CTV (T/N 1.3), CTV (T/N 2.0)), and the PET-edge method (CTV(P-E)) for stereotactic RT planning. Differences among CTVs were evaluated. The brain dose at each CTV and the dose at each CTV defined by C-MET PET using MRI as the reference were evaluated.
The Jaccard index (JI) for concordance of CTV (Gd) with CTVs using C-MET PET was highest for CTV (T/N 2.0), with a value of 0.7. In a comparison of pixel values of MRI and PET, the correlation coefficient for cases with higher JI was significantly greater than that for lower JI cases (0.37 vs. 0.20, P = 0.007). D50% of the brain in RT planning using each CTV differed significantly (P = 0.03) and that using CTV (T/N 1.3) were higher than with use of CTV (Gd). V90% and V95% for each CTV differed in a simulation study for actual treatment using CTV (Gd) (P = 1.0 × 10 and 3.0 × 10, respectively) and those using CTV (T/N 1.3) and CTV (P-E) were lower than with CTV (Gd).
The region of C-MET accumulation is not necessarily consistent with and larger than the Gd-enhanced region. A change of the tumor boundary using C-MET PET can cause significant changes in doses to the brain and the CTV.
探讨甲基-C-L-蛋氨酸正电子发射断层扫描（C-MET PET）与钆增强磁共振成像（MRI）之间摄取区域的差异及其对剂量分布的影响，包括肿瘤边界阈值的变化。
2016 年 4 月至 2017 年 10 月，连续 20 例术后放疗（RT）后复发的 3 级或 4 级胶质瘤患者接受了检查。该研究通过假设所有患者均接受 RT 的模拟进行。使用 Gd 增强区域（CTV（Gd））、C-MET PET 的肿瘤/正常组织（T/N）比值为 1.3 和 2.0（CTV（T/N 1.3）、CTV（T/N 2.0））和正电子边缘方法（CTV（P-E））勾画临床靶区（CTV）。评估 CTV 之间的差异。评估每个 CTV 的脑剂量和使用 MRI 作为参考的 C-MET PET 定义的每个 CTV 的剂量。
与 C-MET PET 相比，CTV（Gd）与 CTV 之间的一致性的 Jaccard 指数（JI）以 CTV（T/N 2.0）最高，为 0.7。在 MRI 和 PET 像素值比较中，具有较高 JI 的病例的相关系数明显大于具有较低 JI 的病例（0.37 比 0.20，P=0.007）。在使用每个 CTV 的 RT 计划中，脑的 D50% 差异有统计学意义（P=0.03），使用 CTV（T/N 1.3）的 D50% 高于使用 CTV（Gd）。在使用 CTV（Gd）进行实际治疗的模拟研究中，每个 CTV 的 V90% 和 V95% 差异有统计学意义（P=1.0×10 和 3.0×10，分别），使用 CTV（T/N 1.3）和 CTV（P-E）的 V90% 和 V95% 低于 CTV（Gd）。
C-MET 摄取区域不一定与 Gd 增强区域一致，且大于 Gd 增强区域。使用 C-MET PET 改变肿瘤边界会导致大脑和 CTV 剂量发生显著变化。
