Anthropomorphic phantom measurements for the validation of a treatment planning system.

A series of eight irradiations of an anthropomorphic phantom has been performed as part of a programme of treatment planning system (TPS) validation. The "treatment' configurations used represent a realistic cross section of those carried out routinely in a radiotherapy centre. The dose distributions within the phantom were determined using 75 LiF TLD chips per irradiation and the measured dose distributions were compared with calculations performed on a TPS for three ranges of dose gradient. The accuracy of the technique per measurement point is estimated to be 3% in dose (low dose gradient) and 3 mm in position (high dose gradient). The measurement and data analysis techniques used permit evaluation of a TPS against recently recommended criteria of acceptability although it is noted that is is not possible to isolate TPS performance from factors depending on, for example, open beam data fitting and treatment set up accuracy.