SU-E-T-511: Do Presage 3D Dosimeters Show Dose Fractionation Sensitivity?

Authors


Abstract

Purpose:

To determine whether Presage 3D polymer dosimeter dose response is sensitive to dose delivery fractionation. Bang gels have demonstrated a dose fractionation related dependence in which a single 400 cGy irradiation would produce a different detector response than four 100 cGy irradiations even if delivered closely in time to one another. Such a fractional dependent response in Presage would be detrimental for measuring multi-beam irradiations.

Methods:

Two separate batches of Presage were poured into cuvettes, and a third batch was molded into cuvette shaped blocks. A total of 37 cuvettes/blocks were irradiated in a Cobalt-60 irradiator to 400 cGy within solid water phantoms in either one, eight, or sixteen fractions. Another group of 15 cuvettes were also kept unirradiated and used for background subtraction between the pre-scan and post-scan results. The times between fractional deliveries were held constant at 30 seconds and the Cobalt irradiator dose rate was 49 cGy/min. Each Presage batch has a separate dose sensitivity and therefore fractionation response comparisons were only performed within the same batch. The cuvettes were first pre-scanned the day prior to irradiation and post-scanned the day after irradiation. Other than approximately 3 hours warming time prior to each irradiation and optical density measurement the cuvettes were stored in a refrigerator. All cuvettes were stored in a lightless environment throughout manufacturing and testing. The cuvettes’ optical densities were optically measured at 632 nm with a spectrophotometer.

Results:

No noticeable dose fractionation dependence was detected for any of the three independent batches of Presage for either the eight or sixteen fraction irradiation schemes.

Conclusion:

These results indicate using Presage 3D dosimeters to measure multi-beam photon irradiations common in IMRT, Gamma Knife, and Cyberknife treatment delivery schemes.

Presage dosimeters are made by and trademarked by Heuris Inc. Skillman, NJ. Dr. John Adamovics is a founder of Heuris Inc.

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