High contrast, CdTe portal scanner for radiation therapy

One of the most promising technologies for improving the quality of radiation therapy is the use of real-time systems to produce portal images. A linear array of 256 CdTe photovoltaic detectors attached to a very compact linear scanner, all of which will be mounted in a cassette shaped package to be located under the patient table, is being constructed. The high stopping power of the CdTe allows a high-contrast image to be made using only a single linac pulse per line, resulting in a high-contrast image in under 5 s. This imager, with its scanning head having an area and thickness not very much larger than those of the presently used film cassettes, should be able to be retrofit to most existing accelerators with a minimum of complexity and expense.<>