SU-E-T-292: In-Vivo Blood Oxygen Measurements Via Interstitial Fiber Optic Probe and Photoacoustic Imaging

Abstract

Purpose: Better understanding of hemodynamics and oxygen transport in response to radiation will enable clinicians to optimize radiotherapy treatment regimens. It is well‐known that oxygenated tissue is significantly more responsive to damage caused by irradiation. We sought to explore the real‐time hemodynamics and blood oxygenation dynamics in response to radiation using a novel interstitial fiber‐optic probe and a photoacoustic imaging system. Methods: Mice bearing xenografted tumors composed of a head and neck cancer cell line (UM‐SCC47) and a patient‐derived xenograft (UW‐SCC36) were irradiated (10 Gy). Blood oxygena saturation (S) and blood volume fraction (B) were monitored in real time using an interstitial fiber optic probe as well as a photoacoustic imaging system (using a 21 MHz transducer, and infra red wavelengths of 750 and 850nm on the Vevo LAZR (R)). Results: A significant drop in blood oxygen saturation was found within 15 minutes following irradiation using the interstitial fiber optic probe. Meanwhile, Blood volume fraction remained constant. Preliminary photoacoustic imaging provided evaluation of the spatial characteristics of blood‐oxygen dynamics and showed qualitative agreement with probe measurements. The measurements were compared to gain a better understanding of the fiber optic probe's spatial averaging, also. Conclusion: While development of the interstitial fiber optic probe continues, it appears to provide real‐time assessment of blood‐oxygen dynamics. Correlation of optimal reoxygenation with split dose radiation response is ongoing and may provide insight that could lead to improvements in the delivery of radiation therapy. This is particularly valuable for hypofractionated treatments as this information can guide the timing, size, and number of fractions for radiotherapy treatments. Minalini Lakshman is an employee of the VisualSonics company; however, the company did not provide any financial support for this work.