Dosimetric properties of intraoperative radiation therapy circular applicators with beveled ends

Circular applicators with beveled ends are frequently used in electron-beam intra-operative radiation therapy (IORT). Because the central axis of the beam is not coincident with the main tumor axis, difficulties may arise in determining and specifying the central axis and the related dosimetric parameters. An in-depth study using a Varian Clinac-18 unit adapted for IORT has been undertaken to measure and compare dosimetric properties of beveled applicators. The bevel angles studied were 00, 150, and 300; the beam nominal energies were 6, 9, 12, 15, and 18 MeV. The authors present the results of the study and make recommendations for specification of dosimetric parameters when beveled applicators are used. The clinical significance and applications of these results are discussed