Method for postmastectomy chest wall dosimetry

Postmastectomy chest walls are often irradiated by means of parallel opposed, tangential 60Co fields. The necessary given dose per field to achieve a prescribed tumor dose depends on field size, chest curvature, and field separation. Computer calculations on 50 patients indicate that the given dose is mainly determined by a single parameter, the separation between medial and lateral fields. Over a considerable range, the relationship between given dose and separation is linear. A nomogram was constructed indicating the given dose per field necessary to give 200 rads tumor dose. With this method treatment planning with good dose distribution is simplified.