Studies Relating to 62 MeV Proton Cancer Therapy of the Eye

The 62 MeV proton cyclotron at Clatterbridge Hospital is now being used for the treatment of eye tumours. As part of an on-going study of the Clatterbridge proton beam line, a three-dimensional Monte Carlo program has been developed to model the passage of protons through the various beam modifiers. These include collimators, scattering foils, range shifters and modulators, and are used to provide both beam uniformity and to spread the proton Bragg peak over a tumour volume. The effects of these devices on, for example, the proton energy spectrum and penumbra are calculated and compared with equivalent measurements. A series of microdosimetric measurements has also been made using a planar tissue-equivalent gas filled proportional counter, a redesign of a previous model. Details of the design of this counter, together with measurements on the 62 MeV proton beam are also presented.