Impact of Fat Layers on Lesion Development during HIFU Application — A Precise Experimental Analysis.

High intensity focused ultrasound (HIFU) provides a noninvasive method for thermal tissue destruction. Local changes in acoustic properties occurring in tissue during the heating procedure, referred to in the literature as “thermal lens effect”, lead to ultrasound beam distortion and lesion displacement. In this study we experimentally analyse the impact of fat layers and of prefocal heating in fat tissue on lesion development. For this purpose we used a two layered fat-gel phantom. The optical transparent polyacrylamide gel phantom containing egg white offered the possibility for a precise visualisation and measurement of a lesion displacement. Fat layers with a large prefocal heating act as a converging lens for the incoming ultrasound beam. Both the lesion position and the lesion shape were affected by thermal lensing in fat layers. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]