Gypsum mixtures for compensator construction.

The characteristics and properties of a new material used for the fabrication of compensators are presented. This material is a special, refined gypsum. It requires a factor of 3 less water to prepare than ordinary gypsums and as a result the attenuation properties are stable over time. The material may be used by itself or mixed with fine metal particles to increase the attenuation per unit thickness. Gypsum, gypsum + steel, and gypsum + iron were investigated. The results of attenuation measurements in narrow- and broad-beam geometries appropriate to design of clinical dose modifying compensators are presented. Practical and technical details associated with the use of these materials are given. These compounds are found to be easy to use, versatile, reliable, environmentally safe, and inexpensive. In addition, an example of their use for dose compensation is given.