Speckle tracking and motion compensation for ultrasound-based lesion localization

Speckle is directly related to ultrasonic scattering from tissue microstructure, and thus can serve as a spatial marker for localizing lesions generated by high intensity focused ultrasound (HIFU). By tracking image speckle from one frame to the next using two-dimensional cross-correlation methods, very sensitive measures of tissue displacement can be produced. The method disclosed in this paper uses phase sensitive speckle tracking to measure tissue displacement over the entire image plane at an accuracy of about 1120 to 1/100 of an ultrasonic wavelength in the axial direction, i.e. an accuracy of about 2 /spl mu/m at 4 MHz. The focal size in the most advanced therapeutic system, which is typically larger than 0.1 mm, is several orders of magnitude greater than this displacement measurement accuracy. So phase sensitive speckle tracking can be used to guide therapeutic ultrasound delivery systems. The results generated from experimental data are presented.