为了探索动态对比增强磁共振成像（DCE-MRI）定量参数在预测直肠癌严重急性放射性直肠损伤（RRI）方面的潜力。本回顾性研究纳入了2014年11月至2021年3月期间接受新辅助化疗放疗和直肠MRI（包括DCE-MRI序列）的49例直肠癌患者。两名放射科医师独立测量了DCE-MRI定量参数，包括前向体积转移常数（Ktrans），速率常数（kep），分数性细胞间间质外体积（ve），以及肿瘤远离病变处直肠壁的厚度。根据组织病理学评估，比较了这些参数在轻度和严重急性RRI组之间的差异。进行了受试者工作特征曲线分析，以分析具有统计学意义的参数。纳入了49名患者（平均年龄54岁±12 [标准差]；男性37名），其中严重急性RRI患者25例。严重急性RRI组的Ktrans值低于轻度急性RRI组（0.032 min-1vs 0.054 min-1；p = 0.008），但其他参数（kep、ve和直肠壁厚度）在这两组之间的差异不显著（所有p > 0.05）。Ktrans的受试者工作特征曲线下面积为0.72（95%置信区间：0.57，0.84）。在Ktrans截断值为0.047 min-1时，预测严重急性RRI的敏感性和特异性分别为80%和54%。Ktrans在预测严重急性RRI方面表现出中等的诊断性能。动态对比增强磁共振成像可以为直肠癌患者围手术期管理和治疗策略提供非侵入性和客观的证据。 • 据我们所知，这是第一个评估直肠癌患者对比增强MRI（DCE-MRI）定量参数在预测严重急性辐射性直肠损伤（RRI）方面的预测价值的研究。 • 来自DCE-MRI的前向体积转移常数（Ktrans）表现出中等的诊断性能（AUC = 0.72），可用于预测直肠癌严重急性RRI，敏感性为80%，特异性为54%。 • DCE-MRI是一种有前景的影像标记物，可用于区分直肠癌患者急性RRI的严重程度。 © 2023年。作者（s）独家许可欧洲放射学学会。

To explore the potential of dynamic contrast-enhanced MRI (DCE-MRI) quantitative parameters in predicting severe acute radiation-induced rectal injury (RRI) in rectal cancer.This retrospective study enrolled 49 patients with rectal cancer who underwent neoadjuvant chemoradiotherapy and rectal MRI including a DCE-MRI sequence from November 2014 to March 2021. Two radiologists independently measured DCE-MRI quantitative parameters, including the forward volume transfer constant (Ktrans), rate constant (kep), fractional extravascular extracellular space volume (ve), and the thickness of the rectal wall farthest away from the tumor. These parameters were compared between mild and severe acute RRI groups based on histopathological assessment. Receiver operating characteristic curve analysis was performed to analyze statistically significant parameters.Forty-nine patients (mean age, 54 years ± 12 [standard deviation]; 37 men) were enrolled, including 25 patients with severe acute RRI. Ktrans was lower in severe acute RRI group than mild acute RRI group (0.032 min-1 vs 0.054 min-1; p = 0.008), but difference of other parameters (kep, ve and rectal wall thickness) was not significant between these two groups (all p > 0.05). The area under the receiver operating characteristic curve of Ktrans was 0.72 (95% confidence interval: 0.57, 0.84). With a Ktrans cutoff value of 0.047 min-1, the sensitivity and specificity for severe acute RRI prediction were 80% and 54%, respectively.Ktrans demonstrated moderate diagnostic performance in predicting severe acute RRI.Dynamic contrast-enhanced MRI can provide non-invasive and objective evidence for perioperative management and treatment strategies in rectal cancer patients with acute radiation-induced rectal injury.• To our knowledge, this study is the first to evaluate the predictive value of contrast-enhanced MRI (DCE-MRI) quantitative parameters for severe acute radiation-induced rectal injury (RRI) in patients with rectal cancer. • Forward volume transfer constant (Ktrans), derived from DCE-MRI, exhibited moderate diagnostic performance (AUC = 0.72) in predicting severe acute RRI of rectal cancer, with a sensitivity of 80% and specificity of 54%. • DCE-MRI is a promising imaging marker for distinguishing the severity of acute RRI in patients with rectal cancer.© 2023. The Author(s), under exclusive licence to European Society of Radiology.