Dose contribution to regional lymph nodes from gynecological remote afterloading cobalt-60 sources

Dose contribution to the regional lymph nodes from high dose rate gynecological intracavitary technique was studied. For computer, calculating radiation dosage, rectangular lymphograms were taken. The average dose to point B and obturator nodes was nearly equal, 29-28% of point A dose. The common iliac nodes received the lowest dose, 14% of point A dose on the average. Due to the wide variation in the position of the uterus (deviation and dislocation), the dose at each of the two corresponding points or nodes (right and left side) was never equal. The effect of the uterus deviation and dislocation on the dose distribution was also studied in computer model display. We managed to describe this effect by an exponential curve. Because of the wide variation in the position of the uterus, only the individual dose calculation to the lymph nodes makes it possible to determine the most accurate amount of additional external irradiation.