Effect of changes of bladder volume on biological dosage capacity of the normal organs in three dimensional conformal brachytherapy for vaginal stump

Objective To compare the influence of changes of bladder volume on biological dosage capacity of the normal organs in three dimensional conformal brachytherapy for vaginal stump. Methods A total of 15 gynecological tumors patients were included in this study, and were given three dimensional conformal brachytherapy in vaginal stump. During three-dimensional conformal brachytherapy, the bladder was emptied and infused by saline at a dosage of 50, 100 and 150 mL, respectively. The values of the dose of 2 cm³ of normal organ closest to the radiation source(D_{2 cm³})of small intestine, rectum, bladder and sigmoid colon were compared at different bladder volumes. Results The D_{2 cm³} of small intestine in emptying was higher than 50, 100 and 150 mL saline(P<0.01). The change of bladder volume had no significant effect on values of D_{2 cm³} of rectum, bladder, and sigmoid colon. Conclusion The changes of bladder volume have an impact on D_{2 cm³} of the small intestine, but no influence on the D_{2 cm³} of rectum, sigmoid and bladder. For retrofitting of the vaginal stump, bladder filling of 50 mL is appropriate, which can reduce the dosage of small intestine.