Clinical experience with pi-meson therapy at SIN

The first treatments of patients with the SIN Piotron were initiated in November 1980. In order to develop safe progression of treatment for this new and unique beam configuration, it was planned to treat in phases of increasing complexity. Patients with multiple skin metastases received pion therapy and x-ray therapy in comparable geometric and dosimetric arrangements to separate skin lesions. A scale of acute skin reactions was used to score reactions and the reaction levels were compared. Only two out of six patients were able to complete the scheduled treatments because of technical beam failures; nevertheless it was possible to compare effects from 6 pion treated fields with 11 x-ray treated fields. RBE values of about 1.4 for 4 to 12 fractions corresponded to values reached in similar trials in Los Alamos and Vancouver. The next stage involved the treatment of single larger lesions with up to thirty beams and involved the complicated arrangement of patient immobilization in individual impression moulds in cylindrical treatment shells, the localization by an x-ray positioning device, and treatment inside a cylindrical water bolus. These technical developments will be discussed, together with the dosimetric and clinical results