Shrivastava Rajeev, Umbarkar Rahul B, Sarje M B, Singh K K
Department of Radiotherapy and Oncology, Rural Medical College, Loni, Ahmednagar, Maharashtra, India.
J Med Phys. 2009 Apr;34(2):93-6. doi: 10.4103/0971-6203.51936.
The purpose of this study was to calculate the radiation dose at the anterior rectal wall as per the International Commission on Radiation Units and Measurements (ICRU 38) recommendations and compare it with the dose calculated by the commonly used intrarectal catheter. Dose delivery by brachytherapy to the cervix is limited by the critical structure of the bladder and rectum. In this study the ICRU-38 rectal point was derived by using a radio-opaque gauze piece on the posterior vaginal wall, and the intrarectal point was derived by inserting a rubber catheter with a wire, inside the rectum. A total of 146 applications were performed in 81 patients. Rectal doses were compared for complementary rectal points R1 and R5, R2 and R6, R3 and R7, and R4 and R8, obtained by both methods. The rectal doses at each complementary pair were compared with each other. The average dose at R1 was 5% higher than at R5 (60.57% vs. 55.57%). The average dose at R2 was 1% higher than at R6 (58% vs. 57%). The average dose at R3 was 1.29% higher than at R7 (52.71% vs. 51.42%), and the average dose at R4 was 1.15% higher than at R8 (43% vs. 41.85%). There were many instances where the rectal dose exceeded by more than 15%, from the R1 to R4 points (43, 22, 21, and 11 times, respectively, for R1-R5, R2-R6, R3-R7, and R4-R8 pairs). The difference in dose between R1 and R5 was significant as seen on the statistical tests, i.e., Pair T test, Wilcoxan Signed Ranks test, and Sign test (p value 0.002). The rectal dose obtained by the intrarectal wire method underestimates the actual dose to the rectum when compared to the ICRU-38 method. Thus ICRU-38 recommendations should be strictly adhered to, to reduce late complications.
本研究的目的是根据国际辐射单位与测量委员会（ICRU 38）的建议计算直肠前壁的辐射剂量，并将其与常用的直肠内导管计算出的剂量进行比较。近距离放射治疗对子宫颈的剂量输送受到膀胱和直肠等关键结构的限制。在本研究中，ICRU - 38直肠点是通过在后阴道壁放置不透射线的纱布片得出的，直肠内点是通过将带有金属丝的橡胶导管插入直肠得出的。对81例患者共进行了146次治疗。比较了通过两种方法获得的互补直肠点R1和R5、R2和R6、R3和R7以及R4和R8的直肠剂量。比较了每对互补点的直肠剂量。R1处的平均剂量比R5处高5%（60.57%对55.57%）。R2处的平均剂量比R6处高1%（58%对57%）。R3处的平均剂量比R7处高1.29%（52.71%对51.42%），R4处的平均剂量比R8处高1.15%（43%对41.85%）。从R1到R4点，直肠剂量超过15%的情况有很多（R1 - R5、R2 - R6、R3 - R7和R4 - R8对分别为43次、22次、21次和11次）。在统计检验（即配对T检验、Wilcoxan符号秩检验和符号检验）中，R1和R5之间的剂量差异显著（p值为0.002）。与ICRU - 38方法相比，直肠内金属丝法获得的直肠剂量低估了直肠的实际剂量。因此，应严格遵循ICRU - 38的建议，以减少晚期并发症。
