Room: ePoster Forums
Purpose: The purpose of this work is to evaluate the new Standard Imaging W2 plastic scintillation detector (W2) for use in the types of fields used for stereotactic radiosurgery.
Methods: Prior to testing the W2 in small fields, the W2 was evaluated under large field conditions to assess detector performance. These tests included energy dependence, short-term repeatability, dose-response linearity, angular dependence, temperature dependence and dose rate dependence. Next, profiles of small fields shaped by cones and MLCs were measured using the W2 and IBA RAZOR diode in a scanning water tank. Output factors for cones (4-17.5 mm) and MLC fields (10, 20, 30 mm) were acquired with both detectors. Finally, the dose at isocenter for three radiosurgery plans was measured with the W2 using a spherical phantom.
Results: The W2 exhibited acceptable warm-up behavior, short-term reproducibility, angular dependence, dose rate linearity and dose linearity. The behavior of the W2 was similar to previously reported behavior of the W1 detector. Scanning measurements taken with the W2 and RAZOR were in good agreement, with FWHM and penumbra widths agreeing to within 0.1 mm. The output factors measured by the W2 and RAZOR exhibited a maximum difference for the 4 mm cone (5.9%) and 20-mm MLC field (2.6%). The agreement improved to better than 2.5% when small field correction factors were applied to the RAZOR measurements. For the three measured radiosurgery plans, the W2 agreed with our clinical radiosurgery TPS with an RMS deviation of 0.8%.
Conclusion: The W2 exhibited dosimetric characteristics that are suitable for radiosurgery field measurements. The detector agreed well with corrected measurements from the RAZOR diode for output factors and scanned profiles, as well as clinical composite plan deliveries.
Funding Support, Disclosures, and Conflict of Interest: This research was preformed with a device loaned to us by Standard Imaging, which was returned at the completion of the work. We did not receive financial compensation from Standard Imaging.
Scintillators, Radiosurgery, Small Fields
TH- External beam- photons: Small/nonstandard field experimental dosimetry