Magnetic resonance imaging (MRI) provides excellent visualization of central nervous system (CNS) tumors due to its superior soft tissue contrast. Magnetic resonance-guided radiotherapy (MRgRT) has historically been limited to use in the initial treatment planning stage due to cost and feasibility. MRI-guided linear accelerators (MRLs) allow clinicians to visualize tumors and organs at risk (OARs) directly before and during treatment, a process known as online MRgRT. This novel system permits adaptive treatment planning based on anatomical changes to ensure accurate dose delivery to the tumor while minimizing unnecessary toxicity to healthy tissue. These advancements are critical to treatment adaptation in the brain and spinal cord, where both preliminary MRI and daily CT guidance have typically had limited benefit. In this narrative review, we investigate the application of online MRgRT in the treatment of various CNS malignancies and any relevant ongoing clinical trials. Imaging of glioblastoma patients has shown significant changes in the gross tumor volume over a standard course of chemoradiotherapy. The use of adaptive online MRgRT in these patients demonstrated reduced target volumes with cavity shrinkage and a resulting reduction in radiation dose to uninvolved tissue. Dosimetric feasibility studies have shown MRL-guided stereotactic radiotherapy (SRT) for intracranial and spine tumors to have potential dosimetric advantages and reduced morbidity compared with conventional linear accelerators. Similarly, dosimetric feasibility studies have shown promise in hippocampal avoidance whole brain radiotherapy (HA-WBRT). Next, we explore the potential of MRL-based multiparametric MRI (mpMRI) and genomically informed radiotherapy to treat CNS disease with cutting-edge precision. Lastly, we explore the challenges of treating CNS malignancies and special limitations MRL systems face.
磁共振成像（MRI）凭借其卓越的软组织对比度，为中枢神经系统（CNS）肿瘤提供了优异的可视化效果。由于成本与可行性的限制，磁共振引导放射治疗（MRgRT）长期以来主要应用于初始治疗计划阶段。磁共振引导直线加速器（MRLs）使临床医生能够在治疗前及治疗过程中直接观察肿瘤及危及器官（OARs），这一过程称为在线MRgRT。该创新系统支持基于解剖结构变化的自适应治疗规划，从而确保肿瘤的精准剂量投照，同时最大限度地减少对健康组织的不必要毒性。这些进展对于脑和脊髓等部位的治疗调整至关重要，因为传统的初步MRI与日常CT引导在这些区域的应用效益有限。本文通过叙述性综述，探讨在线MRgRT在各种CNS恶性肿瘤治疗中的应用及相关正在进行的临床试验。对胶质母细胞瘤患者的影像分析显示，在标准放化疗过程中肿瘤总体积会发生显著变化。对这些患者采用自适应在线MRgRT可观察到靶区体积因空腔收缩而减小，从而降低了对未受累组织的辐射剂量。剂量学可行性研究表明，与传统直线加速器相比，MRL引导的颅内及脊柱肿瘤立体定向放疗（SRT）具有潜在的剂量学优势，并能降低并发症发生率。同样，剂量学研究在海马回避全脑放疗（HA-WBRT）中也显示出良好前景。接下来，我们探讨基于MRL的多参数MRI（mpMRI）及基因组学指导的放疗技术以尖端精准模式治疗CNS疾病的潜力。最后，我们分析了CNS恶性肿瘤治疗面临的挑战以及MRL系统存在的特殊局限性。
肿瘤(癌症)患者之家