Department of Neuroradiology, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany.
Department of Computer Assisted Clinical Medicine, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany.
J Neuroimaging. 2021 Mar;31(2):297-305. doi: 10.1111/jon.12823. Epub 2020 Dec 22.
To date, treatment response to stereotactic radiosurgery (SRS) in brain metastases (BM) can only be determined by MRI evaluation of contrast-enhancing lesions in a long-time follow-up. Sodium MRI has been a subject of immense interest in imaging research as the measure of tissue sodium concentration (TSC) can give valuable quantitative information on cell viability. We aimed to analyze the longitudinal changes of TSC in BM measured with Na MRI before and after SRS for assessment of early local tumor effects.
Seven patients with a total of 12 previously untreated BM underwent SRS with 22 Gy. In addition to a standard MRI protocol including dynamic susceptibility-weighted contrast-enhanced perfusion, a Na MRI was performed at three time points: (I) 2 days before, (II) 5 days, and (III) 40 days after SRS. Nine BMs were evaluated. The absolute TSC in the BM, the respective peritumoral edemas, and the normal-appearing corresponding contralateral brain area were assessed and the relative TSC were correlated to the changes in BM longest axial diameters.
TSC was elevated in nine BM at baseline before SRS with a mean of 73.4 ± 12.3 mM. A further increase in TSC was observed 5 days after SRS in all the nine BM with a mean of 86.9 ± 13 mM. Eight of nine BM showed a mean 60.6 ± 13.3% decrease in the longest axial diameter 40 days after SRS; at this time point, the TSC also had decreased to a mean 65.1 ± 7.9 mM. In contrast, one of the nine BM had a 13.4% increase in the largest axial diameter at time point III. The TSC of this BM showed a further TSC increase of 80.1 mM 40 days after SRS.
Changes in TSC using Na MRI shows the possible capability to detect radiobiological changes in BM after SRS.
迄今为止，脑转移瘤（BM）立体定向放射外科（SRS）的治疗反应只能通过 MRI 评估增强病变的长期随访来确定。钠 MRI 一直是成像研究的一个热点，因为组织钠浓度（TSC）的测量可以提供关于细胞活力的有价值的定量信息。我们旨在分析 SRS 前后使用 Na MRI 测量 BM 中的 TSC 的纵向变化，以评估早期局部肿瘤效应。
7 名共 12 个未经治疗的 BM 患者接受了 22 Gy 的 SRS。除了包括动态磁敏感对比增强灌注的标准 MRI 方案外，还在三个时间点进行了 Na MRI：（I）SRS 前 2 天，（II）SRS 后 5 天，和（III）SRS 后 40 天。评估了 9 个 BM。评估了 BM 中的绝对 TSC、各自的瘤周水肿以及正常的相应对侧脑区，并将相对 TSC 与 BM 最长轴向直径的变化相关联。
SRS 前，9 个 BM 的 TSC 在基线时升高，平均为 73.4±12.3 mM。在 SRS 后 5 天，所有 9 个 BM 的 TSC 均进一步升高，平均为 86.9±13 mM。SRS 后 40 天，9 个 BM 中有 8 个 BM 的最长轴向直径平均下降 60.6±13.3%；此时，TSC 也下降至平均 65.1±7.9 mM。相比之下，9 个 BM 中有 1 个 BM 的最大轴向直径在时间点 III 增加了 13.4%。该 BM 的 TSC 显示出进一步的 TSC 增加，为 80.1 mM，在 SRS 后 40 天。
使用 Na MRI 测量 TSC 的变化显示出在 SRS 后检测 BM 中放射生物学变化的可能能力。
