Moldable tissue equivalent bolus for high-energy photon and electron therapy

Abstract

In radiation therapy, there is often a need to treat irregular surfaces with electron and photon beams. These surfaces require smoothing to achieve uniform doses at depth and proper buildup of dose at the surface. The surface smoothing and dose buildup is achieved by applying bolus. To deliver a known dose, produce a known central axis depth dose, and beam flatness for successful treatment, it is necessary that water or tissue equivalent bolus material is used. This material must also be able to fill extremely irregular voids. Several moldable materials, currently or formerly used in dental clinics, were evaluated for adequacy as tissue equivalent bolus. Availability was also considered during evaluation. Polyflex, a hydrocolloid, was found to be near water equivalent for electron and photon beams. It was also inexpensive, readily available, and held up well over time.