Spectral analysis of ultrasound backscatter for characterization of HIFU lesions in cardiac tissue high-frequency imaging

Conventional methods of tissue ablation for treatment of cardiac arrhythmia have their limitations, including the requirement for tissue contact and limited ability to create transmural lesions with minimal collateral damage. As part of a larger effort to create an efficient therapeutic ultrasound (US) system for cardiac ablation, this pilot study employed high-frequency US imaging to characterize the temporal evolution of high-intensity focused US (HIFU) lesion formation by rapid M-mode imaging and the spatial extent of lesions by spectral analysis of US backscatter from B-mode images. M-mode imaging was found to be able to detect changes in the tissue due to cavitation. 3D B-mode imaging provided detailed images of lesions as small as 1 mm wide and 3 mm long. The spectral analysis showed that the midband fit and intercept of the linear regression to the calibrated spectra increased after lesion formation, while slope decreased. Together these methods indicate that high-frequency imaging can be an effective tool for HIFU lesion characterization.