SU-E-T-95: Investigation of 3D Dosimetry for an Anthropomorphic Spine Phantom

Abstract

Purpose: To evaluate 3D dosimetry for a spinal cord treatment plan delivery using the Radiological Physics Center's (RPC) anthropomorphic spine phantom.

Methods: The RPC's spine phantom currently uses radiochromic film and thermoluminescent dosimeters (TLD) to evaluate spinal metastases treatments. A second dosimetry insert for the phantom was created to hold a PRESAGE® 3D dosimeter which matched the location of the TLD and film in the original insert. The phantom was CT imaged with each insert and an IMRT treatment plan was developed. The IMRT plan was delivered to the phantom twice; once with each insert. The film and PRESAGE® were scanned on a CCD microdensitometer and optical-CT system, reconstructed to a 2 mm slice width, respectively. The measured dose distributions were compared to the treatment plan calculated dose distribution using RPC in-house developed software or the Computational Environment for Radiotherapy Research (CERR). Film and PRESAGE® dose profiles were taken across several planes and compared for agreement. The distance to agreement (DTA) between the measured data and treatment plan, within the high dose gradient region, was quantified.

Results: The PRESAGE® and plan dose profiles agreed to within 2and 1 mm in the AP and SI directions, respectively. The film and plan also agreed to within 2 mm across all profiles.

Conclusions: The PRESAGE® 3D dosimeter, based on these preliminary data, shows potential as a dosimeter for the RPC's phantom irradiation studies. Future work will add markers to the PRESAGE® insert to allow for a reproducible registration in CERR and a an optical-CT system, reconstructed to a 2 mm slice width dose calibration protocol will be created. CA 100835.

Keywords: Calibration; Charge coupled devices; Computed tomography; Computer software; Dosimetry; Intensity modulated radiation therapy; Medical imaging; Radiation therapy; Thermoluminescent dosimeters.