Standard plan for low dose rate Cs-137

Abstract

The standard treatment plan for low dose rate Cs-137 ideal insertion of carcinoma of cervix has been used for patients in some hospital due to the limitation of time and treatment planning system. To study that individualisation calculation is different or comparable to the standard plan, the treatment plans of 15 patients were selected to compare the calculated dose rate at point A with the standard dose rate. The patients were treated with the standard applicator of 5-6 cm uterine tube long and a pair of ovoids of half small, small or medium size. The insertions were done two times about 2 weeks separation. The loading followed to the Manchester system. The study for 30 insertions showed the average calculated dose rate at point A of 158.58+11.95 cGy/hr compare to the standard dose rate of 155.01 cGy/hr. The average dose rate at point B is 46.23+2.75 cGy/hr which is 29.15% of point A. The dose rate at point A varies from 146.02 cGy/hr to 199.45 cGy/hr which 22 of 30 insertions (73.3%) have the dose rate at point A within 5% of the standard dose rate. The standard dose rate can be used only if the cephalad surface of ovoids are in the same level with the flange of uterine tube. However, the anatomy and the extension of the disease including the skill of the insertor are the limitation factors.