Significance: Real-time information about oxygen delivery to the hepatic graft is important to direct care and diagnose vascular compromise in the immediate post-transplant period.Aim: The current study was designed to determine the utility of visible diffuse reflectance spectroscopy (vis-DRS) for measuring liver tissue saturation in vivo.Approach: A custom-built vis-DRS probe was calibrated using phantoms with hemoglobin (Hb) and polystyrene microspheres. Ex vivo (extracorporeal circulation) and in vivo protocols were used in a swine model (n ¼ 15) with validation via blood gas analysis.Results: In vivo absorption and scattering measured by vis-DRS with and without biliverdin correction correlated closely between analyses. Lin's concordance correlation coefficients are 0.991 for μ a and 0.959 for μ s 0 . Hb measured by blood test and vis-DRS with (R 2 ¼ 0.81) and without (R 2 ¼ 0.85) biliverdin correction were compared. Vis-DRS data obtained from the ex vivo protocol plotted against the PO 2 derived from blood gas analysis showed a good fit for a Hill coefficient of 1.67 and P 50 ¼ 34 mmHg (R 2 ¼ 0.81). A conversion formula was developed to account for the systematic deviation, which resulted in a goodness-of-fit R 2 ¼ 0.76 with the expected oxygen dissociation curve. Conclusions:We show that vis-DRS allows for real-time measurement of liver tissue saturation, an indicator for liver perfusion and oxygen delivery.

Proper ventilation of a patient with an endotracheal tube (ETT) requires proper placement of the ETT. We present a sensitive, noninvasive, operator-free, and cost-effective optical sensor, called Opt-ETT, for the real-time assessment of ETT placement and alerting of the clinical care team should the ETT become displaced. The Opt-ETT uses a side-firing optical fiber, a near-infrared light-emitting diode, two photodetectors with an integrated amplifier, an Arduino board, and a computer loaded with a custom LabVIEW program to monitor the position of the endotracheal tube inside the windpipe. The Opt-ETT generates a visual and audible warning if the tube moves over a distance set by the operator. Displacement prediction is made using a second-order polynomial fit to the voltages measured from each detector. The system is tested on ex vivo porcine tissues, and the accuracy is determined to be better than 1.0 mm. In vivo experiments with a pig are conducted to test the performance and usability of the system.

Hepatocellular carcinoma (HCC) is the sixth most common cancer and tumor resection is feasible in only 25±30% of these patients. Thermal ablation therapies using lasers, radiofrequency waves and microwaves are considered as an alternative treatment for unresectable tumors. Our goal was to develop optical fiber-based laser ablation while monitoring the changes in temperature and tissue properties in real-time. A portable diffuse reflectance spectroscopy (DRS) system consisting of a DRS probe with self-calibration and fiber optic temperature sensor was made. Tissue mimicking phantoms using human hemoglobin powders and polystyrene particles with fixed total number of scatterers were used to calibrate the system. In vivo studies were performed in 8 rats orthotopically implanted with HCC. Temperature sensor was inserted in the center of the tumor via hypodermic needle and DRS fiber was overlaid on the temperature sensor. Ablation was performed by a fiber optic diffuser connected to an 808nm laser using different power settings in pulse mode. The tissue temperature and optical properties were continuously monitored until both plateaued using a custom LabVIEW program. Rats were immediately euthanized, and the ablated liver tissues were collected for histological analysis. The DRS showed average errors of 6.31% and 4.74% in measuring the absorption (μa) and reduced scattering coefficients (μs) of the phantoms respectively. Tumor bearing liver tissues showed a decreasing trend in both μa and μs irrespective of the laser power (1W-2.5W) and the temperatures recorded (50°C to 88°C) in different animals. Histological analysis showed discrete zones of tissue damage from treated regions with hemorrhage in the outer most zone. Changes in optical properties of the ablated tumors with temperatures and histological changes needs further correlation by performing more in vivo studies. Citation Format: Faraneh Fathi, Dilip R. Maddirela, Venkateswara Rao Gogineni, Sarah B. White, Bing Yu. Real-time measurement of temperature and tissue damage during laser photothermal ablation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2776.