Dec 10, 2013

A Review of Numerical and Experimental Compensation Techniques for Skull-Induced Phase Aberrations in Transcranial Focused Ultrasound

Adamos Kyriakou, Esra Neufeld, Beat Werner, Margarethus Paulides, Gabor Szekely, and Niels Kuster, International Journal of Hyperthermia, Volume 30, Issue 1, pp. 36-46, February 2014, online December 10, 2013

Transcranial focused ultrasound (tcFUS) is an attractive noninvasive modality for neurosurgical interventions. The presence of the skull, however, compromises the efficiency of tcFUS therapy, as its heterogeneous nature and acoustic characteristics induce significant phase aberrations and energy attenuation, especially at the higher acoustic frequencies employed in tcFUS thermal therapy. These aberrations may distort and shift the acoustic focus as well as induce heating at the patient’s scalp and skull bone.

Phased array transducers feature hundreds of elements that can be driven individually, each with its own phase and amplitude. This feature allows for compensation of skull-induced aberrations by calculation and application of appropriate phase and amplitude corrections. In this paper, we illustrate the importance of precise refocusing and provide a comprehensive review of the wide variety of numerical and experimental techniques that have been used to estimate these corrections.

The scientific impact of this study can be summarized as:

  • Overview of the current state of tcFUS interventions used in medical centers around the world for treatment of various neuropathic conditions, recently completed and ongoing clinical trials, and reported complications.
  • Comprehensive overview of over 20 years of in vitro, in vivo, and in silico approaches to research in the field of skull-induced aberration corrections.
  • Critical assessment of different tcFUS techniques, their strengths and shortcomings, as well as the necessary provisions required for the individual techniques to be applied in the clinical environment.