ESTRO 2023 - Abstract Book

S468

Sunday 14 May 2023

ESTRO 2023

Results Measurements revealed a water equivalent ratio (WER = WET/density) ranging from 0.91 to 1.52 with a measurement uncertainty below 1%. From the determined HU values of all materials the mean and standard deviation (SD) were derived (see Fig1b for HIPS) and subsequently used to calculate the WER (Fig2). For four materials a difference of less than 3% between predicted and measured values was found. These were NY-12 (measured: 1.01 ± 0.01; predicted: 1.00 ± 0.01), ABS (1.04 ± 0.01; 1.02 ± 0.01), NY-FDM (1.08 ± 0.01; 1.07 ± 0.01) and PLA (1.09 ± 0.01; 1.07 ± 0.01). The difference between prediction and measurement was larger 3% for HIPS (lowest measured WER = 0.91 ± 0.01; predicted: 0.87 ± 0.04), ELA, WR, TGH and DUR (highest measured WER = 1.52 ± 0.01; predicted: 1.35 ± 0.01). The predicted WER SD was largest for HIPS (4.7%), while for the other materials SD ranges between 0.1%-1.3% were found.

Conclusion The investigated 3D printed materials will enable efficient manufacturing of E2E test phantoms for proton therapy. The most promising surrogates seem to be ABS for soft tissue, Nylon-12 for breast/fatty tissue and PLA/FDM-Nylon for skin/cartilage. The next steps will include producing human prototypes with various inserts for dosimetry, e.g. a neck phantom capable of mimicking patient weight loss. [1] Schneider, U. et al. (1996) - doi.org/10.1088/0031-9155/41/1/009 [2] Peters et al. (2021) - doi.org/10.1016/j.radonc.2021.07.019 PD-0586 Design and assembly of a non-invasive radiation detector to measure the AIF in dynamic PET. L. Carroll 1 , Y. Daoud 2 , S.A. Enger 3,2 1 McGill University, Biomedical Engineering, Montreal, Canada; 2 Jewish General Hospital, Lady Davis Institute, Montreal, Canada; 3 McGill University , Oncology, Medical Physics Unit, Montreal, Canada Purpose or Objective The presence of hypoxic regions in tumor volumes reduces the effectiveness of common treatment techniques including radiotherapy, chemotherapy and immunotherapy. It is possible to map these hypoxic volumes using F-18-fluoromisonidazole (FMISO) dynamic positron emission tomography (dPET). Tumor hypoxia can then be used to predict response to therapy, perform radiotherapy dose escalation and other treatment optimizations. To perform dPET, the time-course activity concentration in the patient’s arteries, called the arterial input function (AIF), must be measured. The gold-standard method to measure the AIF is through arterial cannulation to sample arterial blood throughout the dPET scan. This process imposes a large burden on centres who wish to perform dPET scans. Our lab is developing a non-invasive radiation detector