Department of Radiation Medicine & Applied Sciences, UC San Diego Health, La Jolla, CA 92093, United States; Department of Radiation Oncology, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136, United States.
Department of Radiation Oncology, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136, United States.
Phys Med. 2024 Mar;119:103316. doi: 10.1016/j.ejmp.2024.103316. Epub 2024 Feb 9.
MRI-linear accelerator (MRI-Linac) systems allow for daily tracking of MRI changes during radiotherapy (RT). Since one common MRI-Linac operates at 0.35 T, there are efforts towards developing protocols at that field strength. In this study we demonstrate the implementation of a post-contrast 3DT1-weighted (3D-T1w) and dynamic contrast-enhancement (DCE) protocol to assess glioblastoma response to RT using a 0.35 T MRI-Linac.
The protocol implemented was used to acquire 3D-T1w and DCE data from a flow phantom and two patients with glioblastoma (a responder and a non-responder) who underwent RT on a 0.35 T MRI-Linac. The detection of post-contrast-enhanced volumes was evaluated by comparing the 3DT1w images from the 0.35 T MRI-Linac to images obtained using a 3 T scanner. The DCE data were tested temporally and spatially using data from a flow phantom and patients. K maps were derived from DCE at three time points (a week before treatment-Pre RT, four weeks through treatment-Mid RT, and three weeks after treatment-Post RT) and were validated with patients' treatment outcomes.
The 3D-T1w contrast-enhancement volumes were visually and volumetrically similar between 0.35 T MRI-Linac and 3 T. DCE images showed temporal stability, and associated K maps were consistent with patient response to treatment. On average, K values showed a 54 % decrease and 8.6 % increase for a responder and non-responder respectively when Pre RT and Mid RT images were compared.
Our findings support the feasibility of obtaining post-contrast 3D-T1w and DCE data from patients with glioblastoma using a 0.35 T MRI-Linac system.
磁共振直线加速器（MRI-Linac）系统可在放射治疗（RT）期间对 MRI 变化进行日常跟踪。由于一种常见的 MRI-Linac 工作在 0.35T 下，因此正在努力开发该场强下的协议。在这项研究中，我们展示了使用 0.35T MRI-Linac 实施磁共振对比增强 3D-T1 加权（3D-T1w）和动态对比增强（DCE）协议以评估胶质母细胞瘤对 RT 反应的方法。
实施的协议用于从流量体模和两名接受 0.35T MRI-Linac 放射治疗的胶质母细胞瘤患者（应答者和非应答者）中获取 3D-T1w 和 DCE 数据。通过将 0.35T MRI-Linac 的 3DT1w 图像与使用 3T 扫描仪获得的图像进行比较，评估了增强后体积的检测。使用流量体模和患者的数据对 DCE 数据进行了时间和空间测试。从 DCE 获得 K 图，时间点为治疗前一周（Pre RT）、治疗中四周（Mid RT）和治疗后三周（Post RT），并与患者的治疗结果进行验证。
0.35T MRI-Linac 和 3T 之间的 3D-T1w 增强体积在视觉上和体积上相似。DCE 图像显示出时间稳定性，相关的 K 图与患者对治疗的反应一致。平均而言，当比较 Pre RT 和 Mid RT 图像时，应答者和非应答者的 K 值分别降低了 54%和增加了 8.6%。
我们的研究结果支持使用 0.35T MRI-Linac 系统从胶质母细胞瘤患者中获取磁共振对比增强 3D-T1w 和 DCE 数据的可行性。
