A solid water phantom material for radiotherapy x-ray and gamma-ray beam calibrations.

The formulation, manufacture and testing of an epoxy resin-based solid substitute for water is presented. This "solid water" has radiation characteristics very close volumetrically to those of water. When it is used as a dosimetry phantom for x- and gamma-ray beams in the radiotherapy range, phantom-to-water corrections and density corrections are eliminated. Relative transmission measurements have shown that the transmission through 10 cm of solid water is within 0.2% of that through an equal thickness of water for x and gamma rays. The use of this material for calibration phantoms can help achieve the goal of radiotherapy beam calibrations within +/- 1.0% of the true dose rate, easier to achieve.