Angular dependence of an EDGE detector in small fields in clinical settings

Relative output dose was evaluated while changing the gantry angle and couch angle using an EDGE diode detector in a clinical setting. An ELEKTA cone collimator used in stereotactic radiosurgery (SRS) was used for measurements. We place the edge detector at a depth of 10 cm of solid phantom (30 × 30 × 20 cm 3 ) with a source to axis distance (SAD) of 100 cm. The relative output dose obtained by the EDGE detector was measured while the cone was mounted and the gantry angle was changed under the conditions of 0°, 45°, 90°, 315°, and 270°. As the distance of the passing beam increases as the gantry angle increases at table angle 0°, the intensity of the beam decreases and has a minimum value at the angle of 56.3°, 123.7°, 236.3°, and 303.7°. The sensitivity of output was highest in the anterior direction, and it showed a tendency to decrease in the posterior direction. It can be seen that the relative dose decreases around 60 and 120 degrees according to the change of the table angle, which is thought to be due to the change in beam transmittance according to the beam passing distance and the structure of the EDGE detector, and the sensitivity of the detector. It is also meaningful to report the dependence of the output dose on the angle when measuring using the phantom used in actual clinical practice.