The dosimetric properties of an applicator system for intraoperative electron‐beam therapy utilizing a Clinac–18 accelerator

Abstract

A prototype electron applicator system providing circular and rectangular fields for use in intraoperative electron beam therapy [for cancer] with a Varian Clinac 18 linear accelerator was fabricated. The dosimetric properties of this system for a variety of electron-beam energies, applicator sizes and X-ray collimator settings was documented. Significant findings include: surface dose values are in excess of 90% for electron energies of 12 MeV and above; for the 18-MeV beam, the deepest depth where the central axis dose is 90% of its maximum value is in excess of 50 mm for circular applicators whose diameters are in excess of 5 cm; and the treatment time to deliver 1000 rad given dose (at a given dose rate of 300 MU/min) is on the order of 3-4 min. Cross-field behavior is acceptable for the intended application and X-ray contamination is < 4% for any applicator/electron energy combination. A system for irregular field blocking and TLD [thermoluminescent dosimetry] verification dosimetry was developed.