HIFU tissue lesion quantification by optical coherence tomography

Heating of tissue by high-intensity focused ultrasound (HIFU) can result in sufficient temperature elevation to cause irreversible changes in the tissue structure. The contiguous volume occupied by these changes, a lesion, and the extent of the tissue changes may be quantified histologically or estimated through techniques such as ultrasonic elastography. We have shown that changes in tissue optical scattering could be used as a proxy to improve sensing and imaging of HIFU lesion formation as an alternative to thermometry. Optical coherence tomography (OCT) is a light-based method appropriate for optically accessible tissues, which we have used to quantify lesion volume, shape, and quality based upon the irreversible changes in optical scattering that occurs with protein denaturation. We have adapted OCT to take into account changes in optical polarization of the tissue, providing sensitivity to changes in the collagen orientation of skin with heating. This technique has potential in detecting antecedents of skin burn during HIFU exposures, thereby increasing safety and reducing treatment times.