Cancer Care Services, Royal Brisbane and Women's Hospital, Butterfield Street, Herston, Queensland 4029, Australia; School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
Cancer Care Services, Royal Brisbane and Women's Hospital, Butterfield Street, Herston, Queensland 4029, Australia; School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
Med Dosim. 2021;46(4):342-346. doi: 10.1016/j.meddos.2021.03.008. Epub 2021 Apr 29.
Treating pregnant women in the radiotherapy clinic is a rare occurrence. When it does occur, it is vital that the dose received by the developing embryo or foetus is understood as fully as possible. This study presents the first investigation of foetal doses delivered during helical tomotherapy treatments. Six treatment plans were delivered to an anthropomorphic phantom using a tomotherapy machine. These included treatments of the brain, unilateral and bilateral head-and-neck, chest wall, and upper lung. Measurements of foetal dose were made with an ionisation chamber positioned at various locations longitudinally within the phantom to simulate a variety of patient anatomies. All measurements were below the established limit of 100 mGy for a high risk of damage during the first trimester. The largest dose encountered was 75 mGy (0.125% of prescription dose). The majority of treatments with measurement positions less than 30 cm fell into the range of uncertain risk (50 - 100 mGy). All treatments with measurement positions beyond 30 cm fell into the low risk category (< 50 mGy). For the cases in this study, tomotherapy resulted in foetal doses that are at least on par with, if not significantly lower than, similar 3D conformal or intensity-modulated treatments delivered with other devices. Recommendations were also provided for estimating foetal doses from tomotherapy plans.
在放射治疗诊所中治疗孕妇是一种罕见的情况。当这种情况确实发生时，尽可能全面地了解胚胎或胎儿所接受的剂量至关重要。本研究首次调查了螺旋断层放疗治疗过程中胎儿所接受的剂量。使用一台断层放疗机向一个人体模型提供了 6 个治疗计划，包括脑部、单侧和双侧头颈部、胸壁和上肺的治疗。通过在人体模型内的不同位置纵向放置电离室来测量胎儿剂量，以模拟各种患者解剖结构。所有测量值均低于第一孕期损伤风险 100 mGy 的既定限值。所遇到的最大剂量为 75 mGy（处方剂量的 0.125%）。在测量位置小于 30 cm 的大多数治疗中，处于不确定风险（50-100 mGy）范围内。所有测量位置超过 30 cm 的治疗均属于低风险类别（<50 mGy）。对于本研究中的病例，断层放疗所产生的胎儿剂量至少与其他设备提供的类似 3D 适形或调强治疗相当，如果不是明显更低的话。还提供了从断层放疗计划估算胎儿剂量的建议。
