Validation of treatment planning system data: variation in the modelling of three 6 MV beams for extreme rectangular fields.

The validation of photon beam data on the Helax-TMS treatment planning system at the Northern Centre for Cancer Treatment takes the form of profile and depth dose comparisons against measured data for square fields. With a view to using Helax-TMS to plan fixed source-to-surface distance spine fields, validation of extreme rectangular fields was undertaken, based on guidelines published by the American Association of Physicists in Medicine Radiation Therapy Committee (Task Group report 53). The accuracy with which the Helax-TMS-generated profiles matched those measured varied between treatment machines. For three 6 MV beams in the department, two beams showed agreement to within 2% in the central portion of the field, while the third beam demonstrated differences of up to 4.4% in this region. The disparities were attributed to the modelling of the primary dose for each beam by Helax-TMS.

Patient and staff radiation doses from early radiological examinations (1899-1902).

A source of data on radiographic and fluoroscopic examinations, including radiographic technique factors, was used in conjunction with information about cold-cathode X-ray apparatus to estimate patient and staff radiation doses for the years 1899 to 1902 at the Forth Banks Infirmary, Newcastle-upon-Tyne. Physical evidence from representative apparatus of the period was used with a beam spectral simulation program to characterize the X-ray beam, and information about the electrical supply waveform was produced by experimental operation of a contemporary induction coil. Results are given in terms of skin entrance dose, and these are compared with modern values. An estimate of the annual dose received by the radiographer known to have carried out all of the examinations within this period is also given.