Photoacoustic elastic oscillation and characterization

TL;DR

This paper models photoacoustic elastic oscillations using a mass-spring system, demonstrating improved simulation accuracy and proposing a new method to evaluate biological tissue's mechanical properties through damping oscillation analysis.

Contribution

It introduces a novel elastic oscillation model for photoacoustic signals and shows its potential for tissue mechanical property characterization.

Findings

The proposed model aligns better with experimental signals than traditional models.

Photoacoustic damping oscillation can evaluate tissue relaxation time and mechanical properties.

Experimental validation confirms the model's effectiveness in tissue characterization.

Abstract

Photoacoustic imaging and sensing have been studied extensively to probe the optical absorption of biological tissue in multiple scales ranging from large organs to small molecules. However, its elastic oscillation characterization is rarely studied and has been an untapped area to be explored. In literature, photoacoustic signal induced by pulsed laser is commonly modelled as a bipolar "N-shape" pulse from an optical absorber. In this paper, the photoacoustic damped oscillation is predicted and modelled by an equivalent mass-spring system by treating the optical absorber as an elastic oscillator. The photoacoustic simulation incorporating the proposed oscillation model shows better agreement with the measured signal from an elastic phantom, than conventional photoacoustic simulation model. More interestingly, the photoacoustic damping oscillation effect could potentially be a useful characterization approach to evaluate biological tissue's mechanical properties in terms of relaxation time, peak number and ratio beyond optical absorption only, which is experimentally demonstrated in this paper.