Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, No.440 Jiyan road, Huaiyin district, Jinan City, 250117, Shandong Province, China.
Radiat Oncol. 2021 Sep 17;16(1):179. doi: 10.1186/s13014-021-01907-1.
PURPOSE/OBJECTIVE(S): The purpose of the study was to assess the uterus motions and bladder volume changes of fractional movements in cervical sites throughout the external beam radiotherapy (EBRT) treatment.
MATERIALS/METHODS: A prospective online MR imaging tracking study was conducted in EBRT 43 patients with at least 4 scans during each treatment (before: ultrasound scan, MRI scan, CBCT scan, after: MRI scan) were included. In order to improve the treatment repeatability, each patient was instructed to empty the bladder and drink 500 ml water 1 h before CT simulation and each treatment. If the ultrasound scan result reached the CT simulation volume of bladder, the treatment began. Bladder was outlined on the T2 weighted axial sequence and CBCT image by the two observers to avoid the influence of contouring. The data of bladder volume and scanning time were accurately recorded. The bladder volumes, filling rates and uterus motion were retrospectively analyzed by MIM software.
Inter-fraction variation of the bladder volume was significant (p < 0.0001). Intra-fraction mean increase of the bladder volume was modest (30 cc) but significant (p < 0.001). Both inter- and intra-fraction of the uterus motion were significant. The average time between the pre-and post-fraction MRI scans was 27.82 ± 7.12 min (range 10-55 min) for IMRT plans and 24.14 ± 5.86 min (range7-38 min) for VMAT plan. Average bladder filling rate was 3.43 ml/min. The bladder filling rate did not change significantly with the course of treatment, but the bladder was more intolerant.
This is the most detailed assessment of intra-fraction and inter-fraction motion during EBRT for cervical cancer. Finally, this study will inform appropriate treatment margins for online adaptive radiotherapy. We suggest that at least one image scan is needed before the EBRT. The portable US scanner provides a quick but unreliable measurement of the bladder volume. There is a significant statistical difference between the results of ultrasonic scanning and that of image scanning.
本研究旨在评估宫颈癌外照射放疗（EBRT）过程中宫颈部位分次运动时子宫运动和膀胱容积变化。
本研究为前瞻性在线磁共振成像（MRI）跟踪研究，共纳入 43 例 EBRT 患者，每位患者至少在每次治疗期间进行 4 次扫描（治疗前：超声扫描、MRI 扫描、锥形束 CT 扫描、治疗后：MRI 扫描）。为了提高治疗重复性，每位患者均被要求在 CT 模拟和每次治疗前 1 小时排空膀胱并饮用 500ml 水。如果超声扫描结果达到 CT 模拟时的膀胱容积，则开始治疗。两位观察者在 T2 加权轴位序列和 CBCT 图像上勾画膀胱，以避免勾画的影响。准确记录膀胱容积和扫描时间的数据。使用 MIM 软件回顾性分析膀胱容积、充盈率和子宫运动。
膀胱容积的分次间变化具有统计学意义（p<0.0001）。膀胱容积的分次内平均增加量较小（30cc）但具有统计学意义（p<0.001）。子宫运动的分次内和分次间均有统计学意义。预分次和后分次 MRI 扫描之间的平均时间分别为调强放疗（IMRT）计划 27.82±7.12 分钟（范围 10-55 分钟）和容积旋转调强放疗（VMAT）计划 24.14±5.86 分钟（范围 7-38 分钟）。平均膀胱充盈率为 3.43ml/min。膀胱充盈率在治疗过程中没有明显变化，但膀胱的耐受性更差。
这是对宫颈癌 EBRT 过程中分次内和分次间运动的最详细评估。最后，本研究将为在线自适应放疗提供适当的治疗靶区边界。我们建议在 EBRT 前至少进行一次图像扫描。便携式超声扫描仪可快速但不可靠地测量膀胱容积。超声扫描结果与图像扫描结果之间存在显著的统计学差异。
