Gruneisen Parameter Analyzer: Calibration and Validation

The Grüneisen Parameter (Γ) Analyzer, a device that can measure the energy conversion efficiency of biological samples in a photoacoustic system, is calibrated using aqueous ink dilutions. Validation of the analyzer gives Γ-ethanol= 0.72 ± 0.06

Quantitative photoacoustic integrating sphere (QPAIS) platform for absorption coefficient and Gruneisen parameter measurements: Demonstration with human blood

Quantitative photoacoustic imaging in biomedicine relies on accurate measurements of relevant material properties of target absorbers. Here, we present a method for simultaneous measurements of the absorption coefficient and Grüneisen parameter of small volume of liquid scattering and absorbing media using a coupled-integrating sphere system which we refer to as quantitative photoacoustic integrating sphere (QPAIS) platform. The derived equations do not require absolute magnitudes of optical energy and pressure values, only calibration of the setup using aqueous ink dilutions is necessary. As a demonstration, measurements with blood samples from various human donors are done at room and body temperatures using an incubator. Measured absorption coefficient values are consistent with known oxygen saturation dependence of blood absorption at 750 nm, whereas measured Grüneisen parameter values indicate variability among five different donors. An increasing Grüneisen parameter value with both hematocrit and temperature is observed. These observations are consistent with those reported in literature

Quantitative blood oxygen saturation imaging using combined photoacoustics and acousto-optics

In photoacoustic spectroscopy (PAS), wavelength dependent optical attenuation of biological tissue presents a challenge to measure the absolute oxygen saturation of hemoglobin (sO 2). Here, we employ the combination of photoacoustics and acousto-optics (AO) at two optical wavelengths to achieve quantification, where AO serves as a sensor for the relative local fluence. We demonstrate that our method enables compensation of spatial as well as wavelength dependent fluence variations in PAS without a priori knowledge about the optical properties of the medium. The fluence compensated photoacoustic images at two excitation wavelengths are used to estimate the absolute oxygen saturation of blood in a spatially and spectroscopically heterogeneous phantom