Room: Exhibit Hall | Forum 6
Purpose: To evaluate real-time dose measurement accuracy of OARtrac (AngioDynamics, Latham, NY) HDR plastic scintillating detector (PSD) for various HDR applicators and applications including: multi-channel cylinder, Venezia, Simon-Heyman capsules, and Syed.
Methods: A multi-channel cylinder was placed into a female pelvis phantom, while Venezia, Simon-Heyman capsules, and Syed applicators/catheters were each placed into an in-house tissue-mimicking plastisol gel phantom. PSDs were placed into predetermined catheters/channels and CT scans of the phantom with each applicator was taken using our GYN-brachytherapy protocol. An HDR plan was generated using Oncentra (Elekta, version-4.5.2) TPS for each applicator. Locations of the PSDs were determined from CT and expected doses were determined by contouring them, in the preset bone window and level, and determining the PSD_D90%. Each plan was delivered four times, and measured doses were compared to the expected PSD_D90%.
Results: Percent difference between the measured and expected dose for the four detectors placed in the peripheral channels of the cylinder averaged 7.2% (range: -3.8% to 22.8%). For the two PSDs placed in needles anterior and posterior to the Venezia the percent difference averaged -0.46% (range: -2.5% to 1.6%). Percent differences for the four PSDs in the Simon-Heyman capsules and the Syed averaged 2.6% (range: -3.3% to 8.2%) and -3.4 (range: -9.7% to 8.5%), respectively. Of the 56 total measurements for four applicators, 41 of them had a distance-to-agreement (DTA) â‰¤1mm between the measured and planned dose. Largest percent difference of 22.8% had a DTA of 0.4mm because of the steep gradient of 4Gy within the PSD in one of the cylinder channels.
Conclusion: Dose measured by the OARtrac HDR PSDs is comparable to the expected dose. The range of dose within the PSD volume as well as the DTA may be used, in addition to PSD_D90%, to determine the expected dose for clinical applications.
Funding Support, Disclosures, and Conflict of Interest: Rodney Ellis, MD has a consulting contract with Radiadyne (which is now part of AngioDynamics)
Not Applicable / None Entered.