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Interstitial Diffuse Optical Probe with Optical Fiber Spectroscopy to Measure Dynamic Tumor Hypoxia

L Che Fru1*, L DeWerd2 , R Kimple3 , W Culberson4 , M Kissick5 , (1) University of Wisconsin, Madison, Madison, WI, (2) University of WI-Madison/ADCL, Madison, WI, (3) University of Wisconsin, Madison, Madison, WI, (4) university of Wisc Madison, Madison, WI, (5) Accuray, Madison, WI


(Tuesday, 7/31/2018) 1:45 PM - 3:45 PM

Room: Karl Dean Ballroom A1

Purpose: For several decades, hypoxia has been used as a predictor of tumor response. However, hemoglobin oxygen saturation in a tumor is dynamic in space and time. The purpose of this study is to develop a device with a high time resolution that uses optical spectroscopy to measure oxygen saturation in tissue. The well-known technique of photoacoustic imaging was used to benchmark these dynamics.

Methods: An optical probe was designed and manufactured in-house. The probe consisted of two replaceable hollow stainless steel needles with a short bevel point on one end, held parallel to each other by drilled holes in a plastic resin. Two optical fibers, 60 cm in length, were each inserted through one end of each needle to be flushed with the bevel end. The other ends were coupled to a light source and spectrometer, respectively. The needles were inserted in tumors on the hind limbs of immune-compromised mice. Simultaneous measurement with the optical device and photoacoustic imaging was used to determine hemoglobin oxygen saturation in the tumor as inhaled oxygen content was varied at set times.

Results: The light from the spectrometer was fitted to the diffusion equation using a library of absorption coefficients of oxygenated and deoxygenated hemoglobin, water, and fat. The trends in oxygen saturation dynamics observed in photoacoustic imaging were also seen to closely match those calculated from the data obtained via the optical probe.

Conclusion: The application of optical fiber spectroscopy to measure oxygen in tissue has been shown to produce reliable measurement of oxygen with a very high time resolution. Data can be acquired and processed within 10 seconds to obtain the value of oxygen saturation in a tumor. This device could subsequently be used in radiotherapy, especially in hypofractionation as tumor hypoxia becomes more relevant.


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