Transcranial ultrasonic therapy based on time reversal of acoustically induced cavitation bubble signature.
Brain treatment through the skull with high-intensity focused ultrasound can be achieved with multichannel arrays and adaptive focusing techniques such as time reversal. This method requires a reference signal to be either emitted by a real source embedded in brain tissues or computed from a virtual source, using the acoustic properties of the skull derived from computed tomography images. This noninvasive computational method focuses with precision, but suffers from modeling and repositioning errors that reduce the accessible acoustic pressure at the focus in comparison with fully experimental time reversal using an implanted hydrophone. In this paper, this simulation-based targeting has been used experimentally as a first step for focusing through an ex vivo human skull at a single location. It has enabled the creation of a cavitation bubble at focus that spontaneously emitted an ultrasonic wave received by the array. This active source signal has allowed 97 +/- 1.1% of the reference pressure (hydrophone-based) to be restored at the geometrical focus. To target points around the focus with an optimal pressure level, conventional electronic steering from the initial focus has been combined with bubble generation. Thanks to step-by-step bubble generation, the electronic steering capabilities of the array through the skull were improved.
Gâteau
Jérôme
J
Langevin Institute (CNRS UMR 7587), Inserm U979 Wave Physics for Medicine, Ecole Superieure de Physique et Chimie Industrielles de la Ville de Paris, Université Paris VII, Paris, France. jerome.gateau@espci.fr
Marsac
Laurent
L
Pernot
Mathieu
M
Aubry
Jean-Francois
JF
Tanter
Mickaël
M
Fink
Mathias
M
D000465:Algorithms; D003198:Computer Simulation; D006801:Humans; D045423:Microbubbles; D019047:Phantoms, Imaging; D011312:Pressure; D012815:Signal Processing, Computer-Assisted; D012886:Skull / Q000000981:diagnostic imaging*; D013382:Subtraction Technique; D014464:Ultrasonic Therapy / Q000379:methods*; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*