Speaker
Description
Pentacosa-10,12-diynoic acid (PCDA) and its Li salts are used in clinical radiotherapy across a broad range of modalities. The underlying chemical and structural characteristics of these materials however remain poorly understood within the medical physics community. In this work we systematically evaluate the real-time dosimetric performance of three PCDA-based radiochromic formulations, including two commercial analogues, and one novel formulation we developed, under high energy photon (6 and 10 MV) and proton (74 MeV) irradiation. Formulations were coated on polyethylene substrates and irradiated using custom fibre-optic setups enabling real-time transmission measurements at 1-2.5 cm depth. Two distinct absorbance peak positions, centered at ~635 nm ~ 674 nm, were observed as function of lithium molar ratio, introduced during formulation. The novel Li salt of PCDA (674LiPCDA) exhibited non-linear dose response resembling commercial EBT-3, while displaying plate like morphology like PCDA. Results of lithium incorporation demonstrated overall enhancement in apparent dose sensitivity relative to PCDA; however, 674LiPCDA, which has a higher lithium molar ratio compared to its commercial analogue 635LiPCDA, had a 68 ± 2 % lower apparent sensitivity at 25 Gy. All formulations exhibited reduced apparent sensitivity under proton irradiation relative to photons, consistent with LET-dependent quenching effects observed in commercial radiochromic films. Elemental analysis revealed consistent elemental composition for 635LiPCDA and 674LiPCDA, with nearly identical lithium content (1.66% and 1.69%, respectively). ATR-FTIR spectroscopy revealed the absence of the O-H stretching in 674LiPCDA, indicating that, unlike 635LiPCDA, the material is anhydrous and that the hydration plays a significant role in dose response. These results demonstrate that radiochromic dose response is governed by a complex interplay of small-molecule incorporation and chemical composition. This study establishes a framework for the controlled generation of radiochromic dosimeters, paving the way for broad-use, real-time in vivo dosimeter technologies to improve patient outcomes in radiotherapy.
| Keyword-1 | Polymer |
|---|---|
| Keyword-2 | Radiochromic |
| Keyword-3 | Real-time dosimtery |