Optimized MLC-beam arrangements for tangential breast irradiation.

Abstract

Very large numbers of women are treated with tangential breast irradiation after breast-conserving surgery due to mammary carcinoma. The aim of this study was to improve a conventional treatment plan by modifying the dose intensity in the beams to reduce the absorbed dose outside the planning target volume (PTV) and to reduce the absorbed dose variation inside the PTV diotherapy of mammary carcinoma. Treatment planning was performed both with conventional technique and with a simple intensity modulation technique for 12 consecutive patients. In all cases a higher degree of dose conformity was obtained with the dose intensity modulation technique. The relative gain was found to be similar for all patients irrespective of the size of the target volume or the irradiated lung volume. Simple manual intensity modulation can be used to improve the dose distribution in tangential breast irradiation. With modern accelerators the increased time for this technique is less than 2 min per fraction.