由于辐射坏死（RN）和肿瘤复发可能同时存在，因此预测立体定向放射外科（SRS）治疗组织反应的难度很大。我们的研究旨在通过执行纵向肿瘤栖息地分析来预测脑转移SRS后的肿瘤复发，包括复发部位。对83名成年人（平均年龄59.0岁；范围27-82岁；44名男性和39名女性）的103个SRS治疗的脑转移进行了两次连续多参数MRI检查。利用k-means体素聚类法定义基于增强T1-和T2加权图像（结构栖息地）以及基于表观扩散系数（ADC）和脑血管容量（CBV）图像（生理栖息地）的肿瘤栖息地。参考标准基于病理学或脑转移的神经肿瘤反应评估标准（RANO-BM）。使用Cox比例危险回归分析和Dice相似系数评估单次或纵向肿瘤栖息地的参数与复发时间和复发部位之间的关联。两次MRI检查之间的平均间隔为99天。纵向分析显示，低血管细胞栖息地（低ADC和低CBV）的增加与复发风险（危险比[HR]，2.68；95％置信区间[CI]，1.46-4.91；P = 0.001）有关。在单次分析中，固体低增强区域（低T2和低对比增强T1信号）与复发风险（HR，1.54；95％CI，1.01-2.35；P = 0.045）相关。低血管细胞栖息地提示未来的复发部位（Dice相似系数= 0.423）。SRS治疗脑转移后，使用纵向MRI分析观察到增加的低血管细胞栖息地与复发风险（即治疗抵抗）有关并提示复发部位。肿瘤栖息地分析可以帮助指导患有脑转移的患者未来的治疗。版权所有©2023年韩国放射学会。

It is difficult to predict the treatment response of tissue after stereotactic radiosurgery (SRS) because radiation necrosis (RN) and tumor recurrence can coexist. Our study aimed to predict tumor recurrence, including the recurrence site, after SRS of brain metastasis by performing a longitudinal tumor habitat analysis.Two consecutive multiparametric MRI examinations were performed for 83 adults (mean age, 59.0 years; range, 27-82 years; 44 male and 39 female) with 103 SRS-treated brain metastases. Tumor habitats based on contrast-enhanced T1- and T2-weighted images (structural habitats) and those based on the apparent diffusion coefficient (ADC) and cerebral blood volume (CBV) images (physiological habitats) were defined using k-means voxel-wise clustering. The reference standard was based on the pathology or Response Assessment in Neuro-Oncologycriteria for brain metastases (RANO-BM). The association between parameters of single-time or longitudinal tumor habitat and the time to recurrence and the site of recurrence were evaluated using the Cox proportional hazards regression analysis and Dice similarity coefficient, respectively.The mean interval between the two MRI examinations was 99 days. The longitudinal analysis showed that an increase in the hypovascular cellular habitat (low ADC and low CBV) was associated with the risk of recurrence (hazard ratio [HR], 2.68; 95% confidence interval [CI], 1.46-4.91; P = 0.001). During the single-time analysis, a solid low-enhancing habitat (low T2 and low contrast-enhanced T1 signal) was associated with the risk of recurrence (HR, 1.54; 95% CI, 1.01-2.35; P = 0.045). A hypovascular cellular habitat was indicative of the future recurrence site (Dice similarity coefficient = 0.423).After SRS of brain metastases, an increased hypovascular cellular habitat observed using a longitudinal MRI analysis was associated with the risk of recurrence (i.e., treatment resistance) and was indicative of recurrence site. A tumor habitat analysis may help guide future treatments for patients with brain metastases.Copyright © 2023 The Korean Society of Radiology.