Modelling of near-field and far-field diffraction effects of optoacoustic measurements in tissues.

This paper describes the application of a diffraction correction method based on an exact Lommel diffraction formulation applied to an optoacoustic signal. It is already known that the optoacoustic signal contains valuable information about tissue optical properties. Using time-resolved analysis, the tissue optical absorption coefficient can be easily determined. Normally, corresponding experiments measure signals close (a few nuns) to an optoacoustic source. However, it is desirable, in some cases, to perform signal detection in the far field. This leads to changes in pulse shape within optoacoustic signals. The paper presents a new method based on a closed-form formulation to correct diffraction effects in the source/detector geometry. Experimental evidence validates predicted results for the case of a 1mm hydrophone.