Study of uterine configuration and its effect on bladder and rectal dosimetry using the flexible Amersham afterloading system

Forty-six cases of carcinoma of the cervix who underwent intracavitary application using the flexible Amersham afterloading system form the subject of this study. Bladder and rectal dosimetry was done and the angles of version (angle alpha) and degree of shift of the uterus to the right or left of midline (angle beta) were noted. It was observed that there were a significant number of cases (15.4%) in the retroverted range which were required specifications for point A dosimetry. A brief analysis had shown that a higher degree of version appeared to favour higher rectal dose rates but lesser than 6 to 10deg favoured higher bladder dose rates and in the 11 to 15deg showed higher rectal dose rates. Radiographic demarcation of the ovoids to bladder/ rectum interdistance (ZB and ZR) was done. The distances ZB (bladder) and ZR(rectum) varied inversely with the dose rates to the respective organs. A middle uterus (angle beta of 0deg) and an alpha angle range of 160 to 170deg with maximum possible anterior and posterior packing of vagina favoured the least bladder and rectal dose rates, which was seen as contributing to increasing ZB and ZR values. The study showed the importance of a highly individualistic attitude during brachytherapy of carcinoma of the cervix. (author). 11 refs., 4 tabs., 5 figs