Bolus in the treatment of tangential fields in breast cancer

The general understanding that by covering the chest wall with 5 mm thick bolus makes the doses uniform and 100% at the surface is misleading. Unless both the ends are filled with bolus the doses received by the chest wall will be as high as 13%. While treating the chest wall, the bolus should be filled on both sides, i.e. medial and lateral corners. It will be of the shape of inverted wedge on both sides, i.e. greatest thickness at the entry point and then tapering off in the middle. The alignment of the back point and the front beam of cross wire must always be ;hecked after rotating the gantry. While setting up the patient it should always be checked that the angles of the gantry correspond to the theoretical plan. Failures to observe these will lead to differences in planned and actual doses. (author)