Digital storage phosphor radiography for treatment verification in radiotherapy.

The potential of digital storage phosphor radiography (SR) to improve image quality of portal radiographs is evaluated. Conventional film radiographs (FR) and corresponding SR verification images of an anthropomorphic phantom and various irradiation ports of patients were obtained with high-energy photon beams. For both techniques conventional films and storage phosphor screens were placed into a cassette with steel screens. Images were evaluated according to contrast and spatial resolution, delineation of anatomical structures, position of shielding blocks and accuracy of field alignments. Evaluation of 33 pairs of SR and FR portal images yielded a superior contrast resolution of SR in 47% (contrast air-soft tissue) and 37% (bone-soft tissue). Thus SR allows quick and easy detectability of anatomical structures as well as a better definition of block positions and field alignments. Shorter exposure times for computed images may result in a reduction of motion artefacts. SR images are indispensable in modern radiation therapy units, as they are instantly available in a computerized network for further image processing and analysis.