Quality control in the conservative treatment of breast cancer: patient dosimetry using silicon detectors

Twenty patients with early breast cancer were treated with external irradiation, delivered with two tangential beams (6 MV X-rays) using a half-beam block (HBB) and 3-D compensating filters. All patients were immobilized with individualized cellulose acetate casts. Patient dosimetry was performed using p-type silicon detectors. Midline doses were calculated by combined entrance and exit dose measurements. The mean ratio of the measured and the prescribed doses was 96.6 ± 3.8 % at the reference point, 96.8 ± 4.3% at off axis points on the central plane and 96.8 ± 7.6% at off plane points.