The effects of image degradation on ultrasound-guided HIFU
High-intensity focused ultrasound (HIFU) has recently found a wide range ofapplications. In the case of ultrasound-guided HIFU, clutter andphase-aberration can degrade the image quality such that visualization of thetarget can be significantly diminished. In this case the quality of the HIFUintensity deposition can be unknown. We modeled an 8 cm, 1.5 MHz HIFU array anda 6 cm, 2.5 MHz imaging array with propagation of acoustic waves through ahistological characterization of the human abdominal layer using a nonlinear,full-wave simulation method. Modifications were made to the simulated medium inorder to assess the impact of the individual image degradation mechanisms onintensity. For small targets (5 mm diameter lesions), the addition of a 3 cmthick abdominal layer completely obscured the imaging target positioned at 5 cmdepth, however, the deposition of HIFU intensity was not significantly degraded.An average elongation of 0.5mm of the intensity distribution was produced withthe abdominal layer, and the location of the peak focal intensity movedapproximately 0.03mm laterally and 0.9 mm axially. The average peak focalintensity dropped 0.6dB compared to the homogeneous tissue case, despite thepresence of strong phase aberration and reverberation clutter. The intensitydistribution returned nearly to normal when the phase aberration effects wereremoved and remained relatively unchanged when reverberation clutter wasremoved. © 2010 IEEE.
