The observation of an enhanced therapeutic index for FLASH radiotherapy in mice has created interest in practical laboratory-based FLASH irradiators. To date, systems capable of 3D conformal FLASH irradiation in mice have been lacking. We are developing such a system, incorporating a high-current linear accelerator to produce a collimated X-ray beam in a stationary beamline design, rotating the mouse about a longitudinal axis to achieve conformal irradiation from multiple beam directions. The purpose of this work was to evaluate the reproducibility of mouse anatomy under rotation at speeds compatible with conformal FLASH delivery. Three short-hair mice and two hairless mice were immobilized under anesthesia in body weight-specific contoured plastic molds, and subjected to three rotational (up to 3 revolutions/s) and two non-rotational movement interventions. MicroCT images were acquired before and after each intervention. The displacements of 11 anatomic landmarks were measured on the image pairs. The displacement of the anatomical landmarks with any of the interventions was 0.5 mm or less for 92.4% of measurements, with a single measurement out of 275 (11 landmarks × 5 interventions × 5 mice) reaching 1 mm. There was no significant difference in the displacements associated with rotation compared to those associated with moving the immobilized mouse in and out of a scanner or with leaving the mouse in place for 5 min with no motion. There were no significant differences in displacements between mice with or without hair, although the analysis is limited by small numbers, or between different anatomic landmarks. These results show that anatomic reproducibility under rotation speed corresponding to FLASH irradiation times appears to be compatible with conformal/stereotactic irradiation in mice.

观察到小鼠 FLASH 放射治疗的治疗指数提高，这引起了人们对基于实验室的实用 FLASH 辐照器的兴趣。迄今为止，缺乏能够对小鼠进行 3D 适形 FLASH 照射的系统。我们正在开发这样一个系统，它结合了一个大电流直线加速器，以在固定光束线设计中产生准直 X 射线束，围绕纵轴旋转鼠标以实现来自多个光束方向的保形照射。这项工作的目的是评估在与保形 FLASH 传输兼容的速度下旋转鼠标解剖结构的可重复性。三只短毛小鼠和两只无毛小鼠在麻醉下固定在体重特定的轮廓塑料模具中，并受到三个旋转（高达 3 转/秒）和两个非旋转运动干预。在每次干预之前和之后获取 MicroCT 图像。在图像对上测量了 11 个解剖标志的位移。在 92.4% 的测量中，任何干预的解剖标志的位移为 0.5 毫米或更小，275 个（11 个标志×5 干预×​​5 只小鼠）中的单次测量达到 1 毫米。与将固定鼠标移入和移出扫描仪或将鼠标放置在原位 5 分钟不动的情况相比，与旋转相关的位移没有显着差异。有或没有头发的小鼠之间的位移没有显着差异，尽管分析受到少量的限制，或在不同的解剖标志之间。这些结果表明，在对应于 FLASH 照射时间的旋转速度下的解剖学再现性似乎与小鼠的适形/立体定向照射相容。