Sequelae after pediatric cranial radiotherapy (CRT) result in long-term changes in brain structure. While past evidence indicates regional differences in brain volume change, it remains unclear how these manifest in the time course of change after CRT. In this study, we spatiotemporally characterized volume losses induced by cranial irradiation in a mouse model, with a dense sampling of measurements over the first week postirradiation. Wild-type mice received whole-brain irradiation (7 Gy) or sham irradiation (0 Gy) at 16 days of age. In vivo magnetic resonance imaging was performed at one time point before, and 2–4 time points postirradiation in each mouse, with a particular focus on sampling during the first week after cranial irradiation. Volume changes across the brain were measured, and the degree and timing of volume loss were quantified across structures from a predefined atlas. Volume measurements across the brain after cranial irradiation revealed a ∼2-day delay in which volume is not significantly altered, after which time volume change proceeds over the course of four days. Volume losses were 3% larger and emerged 40% slower in white matter than in gray matter. Large volume loss was also observed in the ventricles. Differences in the timing and magnitude of volume change between gray and white matter after cranial irradiation were observed. These results suggest differences in the mechanism and/or kinetics underlying the associated radio-response, which may have implications in development.

儿童颅脑放射治疗 (CRT) 后的后遗症会导致大脑结构的长期变化。虽然过去的证据表明脑容量变化存在区域差异，但目前尚不清楚这些差异在 CRT 后的变化时间过程中如何体现。在这项研究中，我们在小鼠模型中对颅脑照射引起的体积损失进行了时空表征，并在照射后第一周进行了密集的测量采样。野生型小鼠在 16 天龄时接受全脑照射（7 Gy）或假照射（0 Gy）。在每只小鼠照射前的一个时间点和照射后的 2-4 个时间点进行体内磁共振成像，特别关注颅脑照射后第一周的采样。测量了整个大脑的体积变化，并根据预定义的图谱对各个结构的体积损失的程度和时间进行了量化。颅脑照射后的大脑体积测量显示，大约 2 天的延迟期间体积没有显着改变，之后体积变化在四天内持续发生。白质的体积损失比灰质多 3%，出现速度慢 40%。在心室中也观察到大量的容量损失。观察颅脑照射后灰质和白质体积变化的时间和幅度的差异。这些结果表明相关放射反应的机制和/或动力学存在差异，这可能对发育产生影响。