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Progress Toward the Development of a Deformable Anthropomorphic 3D Dosimetric Phantom


T Juang

T Juang1*, S Das1, J Adamovics2, M Oldham1, (1) Duke University, Durham, NC, (2) Rider University, Lawrenceville, NJ

SU-C-105-3 Sunday 1:00PM - 1:55PM Room: 105

Purpose:
Previous work has demonstrated that Presage-Def, a deformable, polyurethane-based radiochromic 3D dosimeter, has strong potential for validating deformable image registration algorithms by tracking optically measured radiation patterns from the deformed shape to the non-deformed shape. Here we present recent investigations into the efficacy of variant Presage-Def formulations with a range of elastic properties in terms of increased dose sensitivity and post-irradiation stability.

Methods:
Eleven formulations of Presage-Def were created from combinations of 3 elastic polyurethane matrices (Shore Hardness 10-20A and 30A) and 7 leuco dyes. Dose sensitivity for each formulation was determined by irradiating cuvettes from 0-8Gy and measuring change in optical density at 633nm. Sensitivity readings were tracked over time to determine stability. Complementary to the small volume studies, a 15.7cm diameter cylindrical Presage-Def deformable dosimeter was created incorporating two air cavities (4.0cm diameter) and a rigid high-Z spine-mimic insert (2.8cm diameter). The dosimeter was subjected to bilateral compression to demonstrate complex, non-uniform deformation, and also irradiated with an 8.6cmx7.4cm field and imaged with optical-CT to investigate feasibility of optical-CT dose readout in a heterogeneous phantom.

Results:
Dose sensitivities ranged from 0.0004-0.0071ΔOD/(Gy*cm) versus 0.0032ΔOD/(Gy*cm) in the original formulation. Highest sensitivity and stability were both seen in formulation PD1 (#2 polyurethane, leuco dye 1-napthal-N,N-diethylamine LMG), which retained 98.6% initial sensitivity over 4 hours whereas the original dropped to 90.6% after 1 hour. X-ray CT images of the prototype phantom with and without compression demonstrated non-uniform deformation of Presage-Def and air cavity geometry while the rigid region remained constant. The irradiated field was clearly visible in 3D dose distributions obtained by optical-CT.

Conclusion:
A Presage-Def formulation was identified from 10 variants with improved dosimetric characteristics. Optical-CT dose readout was achieved in the prototype phantom, demonstrating feasibility of 3D dosimetry in a large deformable dosimeter containing air and rigid bone-mimic inserts.

Funding Support, Disclosures, and Conflict of Interest: NIH R01CA100835

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