Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada.
Department of Medical Biophysics, University of Toronto, Toronto, Canada.
Radiother Oncol. 2021 Sep;162:140-149. doi: 10.1016/j.radonc.2021.07.010. Epub 2021 Jul 17.
To describe the implementation and initial results of using Chemical Exchange Saturation Transfer (CEST) for monitoring patients with central nervous system (CNS) tumours treated using a 1.5 tesla MR-guided radiotherapy system.
CNS patients were treated with up to 30 fractions (total dose up to 60 Gy) using a 1.5 T Elekta Unity MR-Linac. CEST scans were obtained in 54 subjects at one or more time points during treatment. CEST metrics, including the amide magnetization transfer ratio (MTR), nuclear Overhauser effect (NOE) MTR (MTR) and asymmetry, were quantified in phantoms and CNS patients. The signal was investigated between tumour and white matter, across time, and across disease categories including high- and low-grade tumours.
The gross tumour volume (GTV) exhibited lower MTR and MTR and higher asymmetry compared to contralateral normal appearing white matter. Signal changes in the GTV during fractionated radiotherapy were observed. There were differences between high- and low-grade tumours, with higher CEST asymmetry associated with higher grade disease.
CEST MRI using a 1.5 T MR-Linac was demonstrated to be feasible for in vivo imaging of CNS tumours. CEST images showed tumour/white-matter contrast, temporal CEST signal changes, and associations with tumour grade. These results show promise for the eventual goal of using metabolic imaging to inform the design of adaptive radiotherapy protocols.
描述使用化学交换饱和传递（CEST）监测使用 1.5 特斯拉磁共振引导放射治疗系统治疗的中枢神经系统（CNS）肿瘤患者的实施情况和初步结果。
使用 1.5 特斯拉 Elekta Unity MR-Linac 对 CNS 患者进行多达 30 次分割（总剂量高达 60Gy）。在治疗过程中的一个或多个时间点对 54 名患者进行 CEST 扫描。在体模和 CNS 患者中对 CEST 指标（包括酰胺磁共振转移率（MTR）、核奥弗豪瑟效应（NOE）MTR（MTR）和不对称性）进行了定量分析。在肿瘤和白质之间、随时间推移以及在包括高级别和低级别肿瘤在内的疾病类别之间，研究了信号。
与对侧正常白质相比，大体肿瘤体积（GTV）的 MTR 和 MTR 较低，不对称性较高。在分次放射治疗过程中观察到 GTV 中的信号变化。高级别和低级别肿瘤之间存在差异，高 CEST 不对称性与高级别疾病相关。
使用 1.5 特斯拉 MR-Linac 的 CEST MRI 被证明可用于 CNS 肿瘤的体内成像。CEST 图像显示了肿瘤/白质对比度、时间 CEST 信号变化以及与肿瘤分级的关联。这些结果为最终使用代谢成像为自适应放射治疗方案的设计提供信息的目标提供了希望。
