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Thermal Effusivity Changes Predict Radiation Exposure

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N Biswal

N C. Biswal1*, J Sun2, J Anderson3, D Bernard4, V Dandekar5, R Yao6, N Darwish7, Z Wu8, B Jegier9, G Woloschak10, K Griem11, J Chu12, (1) Rush University Medical Center, Chicago, Illinois,(2) Argonne National Laboratory, Argonne, IL, (3) Rush University Medical Center, Chicago, Illinois, (4) Rush University Medical Center, Chicago, IL, (5) Rush University medical center, Chicago, IL, (6) Rush University Medical Center, Chicago, IL, (7) Rush University Medical Center, Chicago, IL, (8) Rush University Medical Center, Chicago, IL, (9) Rush University Medical Center, Chicago, IL, (10) Northwestern University, Chicago, IL, (11) Rush University Medical Center, Chicago, IL, (12) Rush University Medical Center, Oak Brook, IL

SU-E-CAMPUS-J-3 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To evaluate an imaging technique to measure thermal effusivity changes following radiation exposure using 3-dimensional temperature tomography (3DTT). Potential applications include early detection of skin reactions in cancer patients undergoing radiotherapy or large scale monitoring following a radiation disaster.

Methods: We have designed an infrared (IR) imaging system and calibrated with high emissivity materials. The system consisted of an IR camera coupled with two 5000W photographic flash lamps and a portable computer. By inducing a surface temperature change with a flash lamp and measuring the thermal response by taking a rapid set of images using an IR camera, a three dimensional effusivity image can be computed. Four to five week old female SKH-1 hairless mice were irradiated to different doses levels (20 Gy, 10 Gy, 5 Gy and 2 Gy) to the dorsal surface of the right hind thigh in a single fraction using a 1.0 cm Leipzig applicator with an Ir-192 source. Images were obtained 30 minutes pre-irradiation and 0.5 and 1 hour post-irradiation. A 1.0 cm region of interest (ROI) was drawn around the irradiated region at 400 micrometer depth. Mean and standard deviations of apparent effusivity in the ROI were calculated over different time points. A plastic phantom was placed next to mice for reference.

Results: The relative effusivity was computed by taking ratios of effusivities from mouse to that from the phantom. Each mouse s relative effusivity at different time points was normalized to that from pre-irradiation. A12% increase in relative effusivity from the 20 Gy mouse and a 5% from the 2Gy mouse was seen.

Conclusion: The effusivity values are increased following radiation exposure. These preliminary data suggest application of 3DTT in early prediction of radiation exposure. More experiments are warraμμμnted to confirm these findings to extend the study to human subjects.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by CMCR/NIAID/NIH. There is no conflict of interest.

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