Focusing and steering through absorbing and aberrating layers: Application to ultrasonic propagation through the skull
作者:
Mickaël Tanter,
Jean-Louis Thomas,
Mathias Fink,
期刊:
The Journal of the Acoustical Society of America
(AIP Available online 1998)
卷期:
Volume 103,
issue 5
页码: 2403-2410
ISSN:0001-4966
年代: 1998
DOI:10.1121/1.422759
出版商: Acoustical Society of America
数据来源: AIP
摘要:
The time-reversal process is applied to focus pulsed ultrasonic waves through the human skull bone. The aim here is to treat brain tumors, which are difficult to reach with classical surgery means. Such a surgical application requires precise control of the size and location of the therapeutic focal beam. The severe ultrasonic attenuation in the skull reduces the efficiency of the time reversal process. Nevertheless, an improvement of the time reversal process in absorbing media has been investigated and applied to the focusing through the skull [J.-L. Thomas and M. Fink, IEEE Trans. Ultrason. Ferroelectr. Freq. Control43, 1122–1129 (1996)]. Here an extension of this technique is presented in order to focus on a set of points surrounding an initial artificial source implanted in the tissue volume to treat. From the knowledge of the Green’s function matched to this initial source location a new Green’s function matched to various points of interest is deduced in order to treat the whole volume. In a homogeneous medium, conventional steering consists of tilting the wave front focused on the acoustical source. In a heterogeneous medium, this process is only valid for small angles or when aberrations are located in a layer close to the array. It is shown here how to extend this method to aberrating and absorbing layers, like the skull bone, located at any distance from the array of transducers.
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