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Characterization of Novel Water-Equivalent PRESAGE for Megavoltage and Kilovoltage X-Ray Beam Dosimetry

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M Alqathami

M Alqathami1*, A Blencowe2 , G Ibbott3 , (1) UT MD Anderson Cancer Center, Houston, TX, (2) University of South Australia, Adelaide, SA, (3) UT MD Anderson Cancer Center, Houston, TX


SU-E-T-411 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To introduce and characterize novel water-equivalent PRESAGE dosimeters for megavoltage and kilovoltage X-ray beam dosimetry.

Methods: Three novel metal-optimized PRESAGE dosimeters referred to as MO-PRESAGE 1, 2 and 3 were formulated. The radiological properties were key factors that were considered when formulating the new dosimeters. All formulations were prepared in spectrophotometric cuvettes, irradiated with a 6 MV X-ray beam, and the change in optical density was measured using a spectrophotometer. Their sensitivity, post-response stability, and water equivalency were investigated.

Results: The results showed that all three formulations exhibited radiological properties closer to water than any of the commercially available PRESAGE formulations. For example, the novel MO-PRESAGE 1, 2 and 3 have mass densities only 3.9-4.4% higher than that of water, whereas the mass density for the commercial formulation is 5.3% higher. The novel formulations have almost identical Zeff values to that of water (7.42), while the Zeff for the commercial formulation was 3.7% higher than that of water. In addition, the MO-PRESAGE 3 formulation showed mass and energy attenuation coefficients that deviated from those of water by less than 50% relative to the commercial formulation. Furthermore, the reduced Zeff of the three different MO-PRESAGE formulations resulted in a maximum variation in the probability of photoelectric absorption of 1.3 times than of water , compared to 1.8 times that of water for the commercial formulation. MO-PRESAGE 3 was also more sensitive to radiation than the other two new formulations introduced in this work due to the presence of alkylbromide radical initiators in the MO-PRESAGE 3 formulation.

Conclusion: All three novel MO-PRESAGE dosimeter formulations displayed excellent radiological properties, superior to any of the commercially available PRESAGE formulations and thus can be used for the dosimetry of clinical megavoltage and kilovoltage X-ray beams.

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