Dosimetry of Hodgkin's disease therapy using a 4 MV linear accelerator

This report describes a detailed analysis of the dosimetry of the mantle technique for the therapy of Hodgkin's disease when a 4 MV linear accelerator (Varian) is utilized. Doses were determined in a Rando phantom and in vivo using several methods of dosimetry. Significant dose variations, exacerbated by the lead flattening filter, were found. For peripheral doses, where the nodes are near the surface (e.g., neck and axillae), increases of 20-30% were the rule. To adjust for these substantial differences, a shrinking field technique was adopted, obviating the need for complex compensating systems. The doses for the inverted Y field were relatively uniform.