The evaluation of rectal and bladder absorbed doses calculated at the reference points defined by ICRU Report 38 in high dose-rate intracavitary irradiation

We evaluated the clinical usefulness of rectal and bladder absorbed doses calculated at the reference points defined by ICRU Report 38. Fifteen patients with uterine cancers were treated by high dose-rate intracavitary irradiation. Tandem and ovoids (T+O group) were used 32 times and ovoids (O group) 10 times. Rectal reference doses were 7.23±1.28 Gy in T+O group and 6.35±0.99 Gy in O group. These values were higher than the measured rectal doses. Bladder reference doses were 5.59±1.37 Gy in T+O group and 4.65±1.34 Gy in O group. There was no relationship between arrangements of sources and rectal doses in both measured and calculated doses. Distances between the center of ovoids and reference points were 17.5±3.8 mm in T+O group and 16.0±1.3 mm in O group. Rectal and bladder doses calculated at the reference points defined by ICRU Report 38 seem to be superior to doses in point A and measured rectal doses for dose reporting system. More research should be required to evaluate the clinical efficacy of ICRU Report 38 for predicting late radiation injuries. (author)