胶质母细胞瘤在放化疗中的每日演变动态，基于0.35T磁共振成像-线性加速器

胶质母细胞瘤在放化疗过程中的变化主要通过治疗前后磁共振成像（MRI）推断，但由于频繁MRI的物流限制，相关研究较少。我们利用结合MRI-线性加速器（MRI-linac）设备，评估了治疗期间的每日变化。患者在0.35T MRI-linac上进行每日成像，同时在独立高场MRI上在三个时间点进行对比（有无对比剂）。分析肿瘤或水肿（病变）和切除腔的动态变化，并与T1后对比（T1+C）和T2体积进行比对。共纳入36例患者，其中8例仅有腔，12例仅有病变，16例两者皆有。结果显示，64%的患者在治疗期间MRI-linac扫描中出现病变增长，46%的患者腔体缩小。MRI-linac的距离迁移平均为1.3厘米（范围0-4.1厘米）用于病变，0.6厘米（范围0.1-2.1厘米）用于腔体。与独立MRI体积相比，MRI-linac体积的相关R²值分别为：0.991（T2 vs MRI-linac腔体）、0.972（T1+C vs MRI-linac腔体）和0.973（T2 vs MRI-linac病变）。尽管MRI-linac不能区分造影增强和非增强肿瘤，但T1+C与MRI-linac病变之间存在中等相关（R²=0.609）。从治疗前到治疗后（n=35），T1+C和MRI-linac的病变变化一致：缩小（n=6）、增长（n=12）或无变化（n=8），26例（74%）患者表现一致。另有9例（26%）患者在MRI-linac上显示增长，但T1+C部分缩小。没有患者出现T1+C增长而MRI-linac缩小的情况。患者每日成像显示，随着手术切除腔的缩小，边界可能缩减以保护正常脑组织；未切除或肿瘤增长的患者可能需要扩大边界以应对变化。限体积胶质母细胞瘤增强试验可考虑在检测到肿瘤增长时，启用钆增强评价以指导适应性放射治疗。

Glioblastoma changes during chemoradiation therapy are inferred from magnetic resonance imaging (MRI) before and after treatment but are rarely investigated due to logistics of frequent MRI. Using a combination MRI-linear accelerator (MRI-linac), we evaluated changes during daily chemoradiation therapy.Patients with glioblastoma were prospectively imaged daily during chemoradiation therapy on 0.35T MRI-linac and at 3 timepoints with and without contrast on standalone high-field MRI. Tumor or edema (lesion) and resection cavity dynamics throughout treatment were analyzed and compared with standalone T1 postcontrast (T1+C) and T2 volumes.Of 36 patients included in this analysis, 8 had cavity only, 12 had lesion only, and 16 had both cavity and lesion. Of these, 64% had lesion growth and 46% had cavity shrinkage during treatment on MRI-linac scans. The average MRI-linac migration distance was 1.3 cm (range, 0-4.1 cm) for lesion and 0.6 cm (range, 0.1-2.1 cm) for cavity. Standalone versus MRI-linac volumes correlated strongly with R2 values: 0.991 (T2 vs MRI-linac cavity), 0.972 (T1+C vs MRI-linac cavity), and 0.973 (T2 vs MRI-linac lesion). There was a moderate correlation between T1+C and MRI-linac lesion (R2 = 0.609), despite noncontrast MRI-linac inability to separate contrast enhancement from surrounding nonenhancing tumor and edema. From pretreatment to posttreatment in patients with all available scans (n = 35), T1+C and MRI-linac lesions changed together-shrank (n = 6), grew (n = 12), or unchanged (n = 8)-in 26 (74%) patients. Another 9 patients (26%) had growth on MRI-linac, although the T1+C component shrank. In no patient did T1+C lesion grow while MRI-linac lesion shrank.Anatomic changes are seen in patients with glioblastoma imaged daily on MRI-linac throughout the chemoradiation therapy course. As surgical resection cavities shrink, margins may be reduced to save normal brain. Patients with unresected or growing lesions may require margin expansions to cover changes. Limited volume glioblastoma boost trials could consider triggered gadolinium contrast administration for evaluation of adaptive radiation therapy when lesion growth is seen on noncontrast MRI-linac.