MEASUREMENT OF 6-MV X-RAY SURFACE DOSE WHEN TOPICAL AGENTS ARE APPLIED PRIOR TO EXTERNAL-BEAM IRRADIATION

Purpose: Radiation therapy patients are typically warned not to apply lotions, deodorants, or powders to the skin within the treatment area because of the possible increase in surface dose due primarily to a bo lus effect, This study investigates the effect of 15 products, with an d without high atomic number components, on surface dose, Methods and Materials: A Markus-type parallel plate ionization chamber in a polyst yrene phantom was used to measure surface doses for normal application s of the products for small (5 x 5-cm(2)) and a large (25 x 25 cm(2)) field size, Results: The greatest surface dose increase for any produc t was 5.4% (21.8-27.2%) of the d(max) dose for the small field and 1.0 % (43.6-44.6%) for the large field, Products with high-atomic-number c omponents did not increase the surface dose relative to radiation ther apy specialty products. Conclusion: No large increase in surface dose was detected with a normal application of the products, However, the p ossibility exists that an increase in skin reaction may occur owing to chemical irritants in the applied product. (C) 1997 Elsevier Science Inc.