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Proton Dose Validation in a Phantom Beyond TRUFILL N-BCA Embolization Glue

A Mandapaka

A Mandapaka*, A Ghebremedhin , B Patyal , Loma Linda University Medical Center, Loma Linda, CA


SU-F-T-141 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose:To validate the treatment planning system predicted proton dose beyond a heterogeneity (n-BCA glue) by making a measurement in a custom acrylic phantom.

Methods:A custom cubic acrylic phantom was designed for this experiment. A container was designed to fit in the phantom. This container was filled with TRUFILL™ n-Butyl Cyanoacrylate(n-BCA) glue. When the container was placed in the phantom, its center was at a distance of 7.4cm from the entrance. This depth allows us to make measurements around the center of modulation of a 126 MeV proton beam with a 3cm spread-out-Bragg peak. To make measurements at other beam energies, additional acrylic can be added in front of the phantom, to adjust the depth of the heterogeneity. A diamond detector was cross calibrated against a standard cylindrical ion chamber in a 126MeV beam. The diamond detector was then used to make dose measurements beyond the inhomogeneity. The measurement was repeated with the container filled with water. Several measurements were made at each setup, to check reproducibility of measurements.

Results:For the same number of Tic3R1 counts, the dose measured with the diamond detector beyond n-BCA glue was 1.053 times the dose measured beyond the water filled container. This result is in agreement with the measured stopping power of glue (1.06). These measurements were in agreement with the dose predicted by the treatment planning system when the electron density of the heterogeneity was replaced with 1.06 before the dose calculation.

Conclusion:Our initial measurements validate the dose predicted by our treatment plan in the presence of heterogeneity in a phantom. The material tested (n-BCA glue) is commonly used in the treatment of AVM’s prior to an SRS treatment.An error in dose predicted by the treatment plan in the presence of the glue can be detrimental in a single fraction high dose SRS treatment

Funding Support, Disclosures, and Conflict of Interest: I received the n-BCA liquid embolic system samples from Codman and Shurtleff, Inc.

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