Beam characteristics and leakage assessment of an in-house intra-operative electron applicator system

Background: Intraoperative radiation therapy (IORT) technique is used to treat a surgically exposed tumor or tumor bed in the treatment of locally advanced intraabdominal, retroperitoneal, pelvic, thoracic, breast and soft tissue tumors. One way to perform IORT is to use an existing linac and modify the treatment head using an applicator system. In this study the objectives were to design, and build an in-house IORT applicator system, perform an acquisition of dosimetry data and characterize the IORT radiation parameters. Materials and Methods: IORT applicator system developed in this research consists of three flat applicators with inner diameters ( ф) of 3, 5 and 9 cm and one tube ( ф =3 cm) with a 45-degree beveled end. Beam characteristics evaluated include percent depth dose distributions, beam profiles, and leakage dose distributions. Measurements were performed using a Scanditronix (p-si) diode field detector in a Scanditronix (RFAplus) 3-D water phantom. Results: Compared to the standard applicator, depth dose curves for intra-operative cones are shallower surface dose is higher and the maximum peripheral dose is in the order of 9.6%. Conclusion: Using a 10 MeV electron beam, the cone system developed in this study is suitable for treating tumors of width and depth ranges of 1.9-8.4 cm and 14-29 mm, respectively.