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A Novel Phantom for Verifying Patient Orientation Integrity in Radiation Oncology Treatment Planning


C Tien

CJ Tien*, F Liu, BH Curran, ES Sternick, Rhode Island Hospital/Brown Medical Center, Providence, RI

SU-E-T-144 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The American Association of Physicists in Medicine Task Group 53 Report (TG53) describes an extensive list of quality assurance tests for treatment planning systems. One important task described is patient positioning and immobilization.

Methods: The DOVe phantom (Integrated Medical Technologies, Troy, NY) is designed to provide verification of patient orientation. This phantom has dimensions of 25.8 cm by 25.8 cm by 4.5 cm, with a uniform density of negative 315 HU. On one side, there is an engraved head (including nose); on the opposing side, are two engraved feet. Each face includes twelve labels in orientations readable only in the corresponding clinical setup: head/feet first and supine/prone/left/right.

In order to verify patient orientation, the DOVe was scanned on a Philips Brilliance Big Bore CT simulator in all combinations of head/feet first and supine/prone/left/right. Simultaneously, isocenter transfer and physical/TPS distance agreement (other TG53 tests) were verified by placing two metal BBs separated by 2.4 cm upon the face of the phantom as isocenter. After transfer to the TPSs, patient orientation, the isocenter location, and separation distance were verified.

Results: All clinical setup orientations matched between visual inspection, Philips CT software, Eclipse, and Pinnacle. The HU values of the material were within 10 HU range across the entire volume. The isocenter placements were within 1 mm for all orientations. The agreement between physical/TPS distances was within 1 mm for isocenter BBs as well as phantom dimensions.

Conclusion: The DOVe phantom is a novel and useful tool for physicists. While primarily designed to provide a visual confirmation of patient orientation, this phantom is also conducive to performing other TG53 TPS QA tests. These tests include: HU value, physical/TPS distance agreement, and accuracy of isocenter transfer.

Funding Support, Disclosures, and Conflict of Interest: This project was supported by Integrated Medical Technologies.

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