Objective To test and analyze out-of-field organ dose in intracranial tumor radiotherapy with or without wedges and in different radiation field areas.

Methods The absorbed doses of out-of-field organs were measured using a thermoluminescent dosimeter by intracranial tumor radiotherapy simulation in the domestic phantom. The tests were grouped according to radiation field areas and techniques. Common square field techniques do not use wedges, whereas 3D conformal radiotherapy(3D-CRT) uses wedges. The radiation field area was divided into 2 cm × 2 cm and 4 cm × 4 cm fields.

Results The absorbed doses of out-of-field organs ranged from 0.13 mGy to 2.83 mGy per 100 cGy prescription dose. The doses of organs adjacent to the target area are higher after irradiation using the 4 cm × 4 cm field than after irradiation using the 2 cm × 2 cm field(t=-5.023, P=0.004); however, no statistically significant(t= -1.438, P=0.171) difference can be found in organs non-adjacent to the target area. The doses of organs are higher after irradiation using 3D-CRT with a wedge than after irradiation using common square field techniques without a wedge regardless of whether the organs are adjacent to the target area or not(t_头 = -2.805, P=0.038; t_腹 =-11.966, P=0.000).

Conclusions The absorbed doses of out-of-field organs of the patients who received intracranial tumor radiotherapy are associated with radiation field areas and techniques. The doses of organs adjacent to the target area increase as the radiation field area increases in size. Given a uniform radiation field area and prescription dose, the absorbed doses of out-of-field organs irradiated by radiotherapy techniques with wedges are higher than those of organs irradiated by radiotherapy techniques without wedges.