Antolak J A, Strom E A
Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
Med Phys. 1998 Dec;25(12):2388-91. doi: 10.1118/1.598449.
The purpose of this report is to discuss dosimetry and shielding for electron-beam radiotherapy of pregnant patients. Specifically, we have determined fetal dose for a pregnant patient considering electron radiotherapy for a chest wall recurrence of breast cancer. The treatment was simulated using an anthropomorphic phantom, and the measured dose to the unshielded fetus for this plan was 5.3 cGy, a level at which risk to the fetus is uncertain. Therefore abdominal shielding, consisting of 6.6 cm of lead, was used to reduce the dose to the fetus to less than 1.5 cGy, a level considered to be of little risk. We further found that using the lower (instead of upper) variable trimmer bars to define the field edge closest to the fetus resulted in approximately 30% lower dose to the fetus. These results show that it is possible to reduce fetal dose to acceptable limits in electron-beam radiotherapy of the chest wall using the general principles recommended for photon-beam radiotherapy.
本报告的目的是讨论孕妇电子束放射治疗的剂量测定和屏蔽。具体而言，我们针对一名患有乳腺癌胸壁复发并接受电子放疗的孕妇确定了胎儿剂量。使用人体模型模拟治疗过程，该计划中未加屏蔽时测量到的胎儿剂量为5.3厘戈瑞，此剂量水平下对胎儿的风险尚不确定。因此，采用了由6.6厘米铅组成的腹部屏蔽措施，将胎儿剂量降低至1.5厘戈瑞以下，这一水平被认为风险极小。我们还发现，使用较低（而非较高）的可变准直器条来定义最靠近胎儿的射野边缘，可使胎儿剂量降低约30%。这些结果表明，利用光子束放射治疗推荐的一般原则，在胸壁电子束放射治疗中有可能将胎儿剂量降低至可接受的限度。
