Evaluation of the EDGE detector in small-field dosimetry

This study evaluates a new diode detector design for small-field dosimetry. An accurate detector that has a small volume are necessary to compile data for stereotactic radiosurgery (SRS), stereotactic body radiotherapy (SBRT), and intensity-modulated radiotherapy (IMRT). Two semiconductor diode detectors and one ionization chamber were used to measure the profiles, percent depth doses (PDDs), and relative output factors (OFs) of a Novalis 6-MV SRS beam. Profiles and PDD data were collected using 5.0-, 10.0-, 15.0-, 20.0-, 30.0-, and 50.0-mm micro multileaf collimators (mMLCs) at small fields and a 98.0 × 98.0-mm² reference field. OFs were collected for each of the mMLCs. The EDGE diode detector, the diode detector, and the ion chamber (0.007 cc) were used in the study. Detector measurements were performed using the 3D water phantom with a source-to-surface distance of 100-cm at a depth of 1.5-cm. The measurements were analyzed using the IBA OmniPro Accept 7th version software. In addition, all data were compared to Monte Carlo simulations. The semiconductor diodes had similar OFs and PDDs for each of the mMLCs used. The Dmax values of the EDGE diode detector, measured from the PDD, ranged from 8.5 to 14.0-mm with an average of 12.4-mm. The field widths of the EDGE diode detector were found to have similar values. The performance of the EDGE diode detector was comparable for all small-field measurements. Additionally, no evidence of an energy response was observed for the EDGE detectors for a field of 98 × 98-mm². This is particularly important when measuring the relative OF for small fields or gathering larger-sized field data for the commissioning of a treatment planning system.