Determination of optical absorption coefficient with focusing photoacoustic imaging

Abstract

Absorption coefficient of biological tissue is an important factor for photothermal therapy and photoacoustic imaging. However, its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique to quantify the target optical absorption coefficient. It utilizes the ratio of the amplitude of the peak signal from the top boundary of the target to that from the bottom boundary based on wavelet transform. This method is self-calibrating. Factors, such as absolute optical fluence, ultrasound parameters, and Grüneisen parameter, can be canceled by dividing the amplitudes of the two peaks. To demonstrate this method, we quantified the optical absorption coefficient of a target with various concentrations of an absorbing dye. This method is particularly useful to provide accurate absorption coefficient for predicting the outcomes of photothermal interaction for cancer treatment with absorption enhancement.

Phthalocyanine photosensitizers as contrast agents for in vivo photoacoustic tumor imaging

“…1(a)-1(c)). The correlation between absorbance and PA signal as a function of wavelength corroborated our observances as PA signals are projected from the absorbed optical energy, which is derived from the multiplication of the optical absorption coefficient and the light fluence [26]. The minor discrepancies between PA intensity and absorbance can be explained by the changes in light fluence from minor variations in laser intensity during PA imaging.…”

Photoacoustic Microscopy and Computed Tomography: From Bench to Bedside

“…The correction of PA signals for fluence variations, referred to as quantitative photoacoustic sensing and imaging, has been addressed via various approaches (73–76). Additionally, fluence-independent quantities, including acoustic spectra (77; 78) and molecular lifetime (79), have been used to recover blood sO 2 .…”

Small Molecule Optoacoustic Contrast Agents: An Unexplored Avenue for Enhancing In Vivo Imaging

“…have been generated for NIR fluorophores; however, no comparable effort has been expended for optoacoustic contrast agents [ 40 ]. It is well described that, for an optically absorbing body, the amplitude of the ultrasonic wave produced upon excitation will be described by: P = Γ × μ a × Φ where Γ is the Grüneisen parameter of the system, μ a is the absorption coefficient of the absorber, and Φ is the fluence of the excitation light at the absorber [ 41 , 42 , 43 ]. The current, unmet need then is determining the relationship between the Grüneisen parameter and the organic dye structure.…”