Room: AAPM ePoster Library
Purpose: compare the accuracy of Varian Eclipse and Philips Pinnacle for surface dose measurements using a commercial in-vivo dosimeter. The aim is to evaluate the efficacy of the two TPS for clinically relevant in-vivo measurements.
Methods: were taken under four scenarios: photon in-field surface dose, photon out-of-field surface dose, electron in-field surface dose, and electron dose under bolus. In-field measurements were measured on central axis and the out-of-field measurement was taken at 8 cm from the field edge. Measurements were compared to calculated values in Pinnacle (v 16.2) and Eclipse (v 13.6). The average effective depth of the dosimeter was determined by comparing it to Eclipse and Pinnacle. Dose was also calculated along the beam line at several points to determine a distance-to-agreement (DTA) due to the high dose gradient near the surface.
Results: average effective depth of the dosimeter was determined to be 0.7 mm. Pinnacle yielded percent differences within 5% for all cases with a DTA of 0.4 mm, and Eclipse TPS yielded percent differences within 4% for all cases with a DTA of 0.3 mm. The measured electron surface dose showed the closest agreement with each treatment planning system.
Conclusion: and Eclipse are sufficiently accurate for determining surface dose for in-vivo measurements. Measurements were verified to be within manufacturer stated accuracy.