Photoacoustic microscopy of tissue lesions induced by high-intensity focused-ultrasound

Photoacoustic imaging is a recent and rapidly developping technique that can provide images of optical absorption at depth in soft tissue. In this work, photoacoustic imaging is applied to detect tissue lesion induced by high-intensity focused-ultrasound (HIFU).Tissue changes during HIFU therapy include changes in optical tissue properties that may be detected using photoacoustics. However, although it has been demonstrated that HIFU lession could indeed be detected using photoacoustics (Chitnis et al., JBO 15(2), 2010, Cui et al., JBO 15(2), 2010), the exact origin of the observed contrast remains unclear. In this study, lesions induced in different types of biological tissue are imaged in vitro using a photoacoustic microscope. Lesions are induced in the tissue samples with therapeutic ultrasound in the MHz frequency range, and a photoacoustic microscope with imaging frequencies from the MHz to the tens of MHz range, are used to obtain acoustic-resolution photoacoustic images of lesions located at different depths in tissue. Several optical wavelengths, from 532 nm to the therapeutic window in the near-infrared are used to perform a spectroscopic study of the observed contrast.