High power transcranial beam steering for ultrasonic brain therapy

• Published in: Physics in medicine & biology Vol. 48; no. 16; pp. 2577 - 2589
• Main Authors: Pernot, M, Aubry, J-F, Tanter, M, Thomas, J-L, Fink, M
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 21.08.2003; Institute of Physics
• Subjects: Biological and medical sciences; Brain - pathology; Brain - radiation effects; Brain Diseases - therapy; Computer Simulation; Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Hot Temperature; Humans; Liver - pathology; Liver - radiation effects; Medical sciences; Models, Biological; Radiometry - methods; Transducers; Ultrasonic Therapy - instrumentation; Ultrasonic Therapy - methods
• ISSN: 0031-9155; 1361-6560
• DOI: 10.1088/0031-9155/48/16/301

A sparse phased array is specially designed for non-invasive ultrasound transskull brain therapy. The array is made of 200 single elements corresponding to a new generation of high power transducers developed in collaboration with Imasonic (Besançon, France). Each element has a surface of 0.5 cm2 and works at 0.9 MHz central frequency with a maximum 20 W cm(-2) intensity on the transducer surface. In order to optimize the steering capabilities of the array, several transducer distributions on a spherical surface are simulated: hexagonal, annular and quasi-random distributions. Using a quasi-random distribution significantly reduces the grating lobes. Furthermore, the simulations show the capability of the quasi-random array to electronically move the focal spot in the vicinity of the geometrical focus (up to +/- 15 mm). Based on the simulation study, the array is constructed and tested. The skull aberrations are corrected by using a time reversal mirror with amplitude correction achieved thanks to an implantable hydrophone, and a sharp focus is obtained through a human skull. Several lesions are induced in fresh liver and brain samples through human skulls, demonstrating the accuracy and the steering capabilities of the system.