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Initial Results From Multiple Irradiations of An Anthropomorphic Liver Phantom

A Molineu

A Molineu1*, P Alvarez1, C Amador1, T Craig2, M Gillin1, D Followill1, (1) UT MD Anderson Cancer Center, Houston, TX, (2) UHN - Princess Margaret Cancer Centre, Toronto

SU-E-T-410 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To describe the Radiological Physics Center's new anthropomorphic liver phantom and to report the results from the initial irradiations.

Methods: A new imaging and dosimetry insert was created for the RPC's pelvic phantom that includes non-coplanar targets. The polystyrene insert represents the liver and includes two Solid WaterTM targets (PTV1 and PTV2) that mimic liver metastases. PTV1, located in the superior-left-posterior region of the insert, is an ovoid 2 cm in diameter and 2.5 cm long. PTV2, located in the inferior-right-anterior region of the insert is a 3 cm diameter sphere. The insert houses one TLD and 3 planes of radiochromic film in each PTV. The phantom, with a motion table to simulate respiratory motion, was sent to institutions planning to participate in an upcoming RTOG SBRT liver protocol. Institutions were instructed to design and deliver a stereotactic treatment plan that delivered 6 Gy to >=95% of each PTV. The maximum motion of the phantom on the motion table was 1 cm in the superior-inferior direction.

Results: Irradiations from 8 institutions have been analyzed. The acceptance criteria, based on the results of the 8 irradiations, were set at ±7% for the TLD and 85% of the pixels in a region surrounding each PTV passing a ±7%/4 mm global gamma analysis. Five of the 8 irradiations passed these criteria. The three irradiations that did not meet the criteria failed to meet only the film criteria. Breath hold, ITV, gating, and tracking techniques were used to account for motion. Pinnacle, Eclipse, and MultiPlan treatment planning systems were used for planning.

Conclusion: The new liver insert along with a motion table tests the ability of the institution's ability to deliver dose to multiple moving targets and is a useful credentialing tool for clinical trials using SBRT.

Funding Support, Disclosures, and Conflict of Interest: Supported by PHS grant CA10953 and CA081647 from the NCI, DHHS.

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