Yu Cheng, Jozsef Gabor, Apuzzo Michael L J, MacPherson Dana M, Petrovich Zbigniew
Department of Radiation Oncology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
Neurosurgery. 2003 Mar;52(3):687-93; discussion 693. doi: 10.1227/01.neu.0000048479.23069.24.
To assess fetal radiation doses in a pregnant patient undergoing gamma knife stereotactic radiosurgery (GKRS) and to quantify the components of extracranial radiation doses by means of phantom measurements.
A patient in her 25th week of pregnancy received GKRS with the Model C gamma knife for a solitary metastatic melanoma of the brain. A single isocenter with the 14-mm collimator and trunnions was used to deliver 20 Gy to the lesion defined to the 80% isodose line. Fetal radiation doses were assessed with phantom measurements before GKRS and then measured during GKRS. In addition, doses to the lateral canthi, thyroid, sternum, and pelvis were monitored with thermoluminescent dosimeters in 20 consecutive patients during their GKRS. Phantom measurements were also performed to identify extracranial radiation doses to these structures.
Fetal radiation doses were 0.31, 0.20, and 0.15 cGy to the top, middle, and bottom of the uterus, respectively. These approximately corresponded to 0.01% of the maximum tumor dose of 25 Gy. The mean extracranial doses in 20 patients were 36.9, 5.8, 3.3, and 0.6 cGy to the lateral canthi, thyroid, sternum, and pelvis, respectively. Phantom measurements supported the results obtained from the patient measurements and further refined estimates of doses to extracranial sites. These measurements were also compared with those of a previously reported study with the use of the Model U.
Measured radiation doses in a pregnant patient to extracranial sites, including those to the fetus, were very low. We think that GKRS is a safe treatment, particularly with the Model C, and could be recommended to carefully selected patients with brain metastases who are in the second and third trimester of pregnancy.
评估接受伽玛刀立体定向放射外科治疗（GKRS）的孕妇胎儿所受辐射剂量，并通过体模测量量化颅外辐射剂量的组成部分。
一名怀孕25周的患者因脑部孤立性转移性黑色素瘤接受了C型伽玛刀的GKRS治疗。使用带有14毫米准直器和耳轴的单个等中心，将20 Gy的剂量照射到定义为80%等剂量线的病变部位。在GKRS治疗前通过体模测量评估胎儿辐射剂量，然后在GKRS治疗期间进行测量。此外，在20例连续患者进行GKRS治疗期间，使用热释光剂量计监测外眦、甲状腺、胸骨和骨盆的剂量。还进行了体模测量以确定这些结构的颅外辐射剂量。
子宫顶部、中部和底部的胎儿辐射剂量分别为0.31、0.20和0.15 cGy。这些剂量约相当于最大肿瘤剂量25 Gy的0.01%。20例患者的颅外平均剂量分别为：外眦36.9 cGy、甲状腺5.8 cGy、胸骨3.3 cGy和骨盆0.6 cGy。体模测量支持了从患者测量中获得的结果，并进一步完善了颅外部位剂量的估计。这些测量结果还与先前使用U型设备的研究结果进行了比较。
测量的孕妇颅外部位辐射剂量，包括胎儿所受剂量，非常低。我们认为GKRS是一种安全的治疗方法，尤其是C型伽玛刀，可推荐给精心挑选的处于妊娠中晚期且患有脑转移瘤的患者。
