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Cerenkov Emission Spectroscopy for Estimating Tumor Aggressiveness in Head and Neck Cancer

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I Oraiqat

I Oraiqat*, E Al-Snayyan, G Young, R Clarke, R Ten Haken, A Rehemtulla, I El Naqa, University of Michigan, Ann Arbor, MI


SU-F-605-2 (Sunday, July 30, 2017) 2:05 PM - 3:00 PM Room: 605

Purpose: Tumor pH has been suggested as an indicator of its aggressiveness. In this work, we explore the use of Cerenkov Emission Spectroscopy (CES) for interrogating tumor aggressiveness and monitor cancer cell proliferation after various treatment pathways in head and neck cancer.

Methods: UMSCC47 (HPV+) and UMSCC38 (HPV-) head and neck cancer cells were grown in T25 cell culture flasks in a media containing phenol red (PR) as a pH contrast agent. The CES signal is generated using 6MV photons and is coupled into a 20m optical fiber which is fed into a spectrometer. The spectra are normalized by a reference spectrum, which is the CE spectrum of pure water, correcting for both the nonlinearity of the broadband CE spectrum as well as the non-uniform spectral response of the spectrometer. To obtain pH, a ratio of the spectral intensity at 450nm and 560nm is acquired and compared to calibration data. This calibration was done by measuring the intensity ratio of 450nm and 560nm from prepared buffered solutions at various pH values (pH of 6.2 to 8) in 100ml pyrex bottles. A fitted curve comparing this ratio and pH is used for quantification of tumor behavior.

Results: The pH values measured using CES tracked changes between different treatment pathways expected for measured cell survival fractions. The groups with the largest populations were the most acidic. Acidity decreased with decreasing cell populations due to reduced overall metabolic activity in the T25 flask. Using pH, relative treatment resistance was identified between the HPV+ cell line and the HPV- cell line with the HPV- cell line being more resistant to treatment

Conclusion: This work shows the potential for real-time pH measurements during radiotherapy. It was successfully demonstrated in-vitro that CES can be used to monitor cell proliferation post-therapeutic intervention via estimation of tumor pH.

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