High power transcranial beam steering for ultrasonic brain therapy.
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.
Pernot
M
M
Laboratoire Ondes et Acoustique, ESPCI, Université Paris VII, UMR CNRS 7587, 10 rue Vauquelin, 75005 Paris, France.
Aubry
J F
JF
Tanter
M
M
Thomas
J L
JL
Fink
M
M
D001921:Brain / Q000473:pathology / Q000528:radiation effects*; D001927:Brain Diseases / Q000628:therapy*; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006358:Hot Temperature; D006801:Humans; D008099:Liver / Q000473:pathology / Q000528:radiation effects*; D008954:Models, Biological; D011874:Radiometry / Q000379:methods; D014159:Transducers; D014464:Ultrasonic Therapy / Q000295:instrumentation* / Q000379:methods*