Quantitative tissue characterization using discrete wavelet transform of photoacoustic signals: a feasibility study

Abstract

Photoacoustic (PA) imaging is an emerging soft tissue imaging modality which can be efficiently used for tissue characterization. However, quantitative tissue evaluation using PA imaging is very difficult due to complex and nonlinear relationship between PA signal and optical property of tissue. This study introduces a method for extracting quantitative information about the size of regular-shaped PA absorbers using wavelet domain analysis of PA signals and concentration using segmentation. In this study, PA signals corresponding to tissue phantoms containing cylindrical PA absorbers were simulated under different conditions. The detail spectra of the simulated PA signals were computed using suitable mother wavelet and then further analysed to compute PA absorber diameter in terms of a distance parameter. A generalized method was proposed and verified using simulations for simultaneous quantitative recovery of absorber diameter and concentration for tissue phantoms containing PA absorbers with unknown radius and concentration values. The results show that the extracted values of PA absorber diameter as well as PA absorber concentration agree with the actual values of absorber diameter and concentration within certain degree of accuracy.