胶质母细胞瘤在化疗放疗期间每日演变的动态变化：0.35T磁共振成像-线性加速器的观察

胶质母细胞瘤在化疗放疗期间的变化通常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。利用结合MRI与线性加速器（MRI-linac），我们评估了日常化疗放疗中的变化。前瞻性在0.35T MRI-linac上对胶质母细胞瘤患者进行每日成像，并在无对比和有对比的高场MRI上在三个时间点进行扫描。分析肿瘤或水肿（病灶）和切除腔的动态变化，并与单独的T1造影后（T1+C）和T2体积进行比较。在纳入的36例患者中，8例仅有腔，12例仅有病灶，16例两者皆有。在这些患者中，64%的患者在MRI-linac扫描中表现出病灶增长，46%的患者腔体缩小。MRI-linac的平均迁移距离为1.3厘米（范围，0-4.1厘米）为病灶，0.6厘米（范围，0.1-2.1厘米）为腔体。单独MRI与MRI-linac的体积高度相关，R2值分别为：T2与MRI-linac腔体0.991，T1+C与MRI-linac腔体0.972，T2与MRI-linac病灶0.973。尽管MRI-linac无法区分造影增强与非增强肿瘤和水肿，但T1+C与MRI-linac病灶之间存在中等相关（R2=0.609）。从治疗前到治疗后，所有可用扫描（n=35）中，T1+C和MRI-linac病灶共同变化——缩小（n=6）、增长（n=12）或无变化（n=8），共26例（74%）。另外9例（26%）在MRI-linac上显示增长，尽管T1+C部分缩小。没有任何患者在T1+C病灶增长的同时MRI-linac病灶缩小。患者在每日MRI-linac扫描中观察到解剖学变化。随着手术切除腔体收缩，可以减少边界以保护正常脑组织。未切除或病灶增长的患者可能需要扩大边界以覆盖变化。有限体积胶质母细胞瘤增强试验可考虑在观察到非增强MRI-linac上病灶增长时，触发钆对比剂的使用以辅助适应性放疗评估。

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.