Calculation of radiation doses in critical organs compared with in vivo dosimetry during brachytherapy of carcinoma of the uterine cervix.

In a group of 38 patients with carcinoma of the uterine cervix, radiation doses were measured by thermoluminiscent dosimeters (TLDs) placed in catheters introduced into the urinary bladder and rectum during a 24 h uterovaginal application of 226Ra. The values of radiation doses registered by the TLDs were compared to those calculated from roentgenograms made after 24 h. To calculate the radiation doses, we used the program Brachy 9.3-C of the planning unit Evados (Siemens, FRG). Using nonparametric comparison tests, no statistically significant differences were found between the values of radiation doses registered by TLDs and those calculated after 24 h of uterovaginal application of 226Ra. Only in the oral part of the rectum, at a distance of 10 cm and above from the anal orifice, there were differences between doses measured by TLDs and those calculated from roentegenograms made after 24 h of brachytherapy. These differences were caused by the movement of the flexible catheters carrying the TLDs.