Mathieu Pernot, Abstract Co-Author: Nothing to Disclose

Jean-Francois Aubry PhD, Presenter: Nothing to Disclose

Anne-Laure Boch, Abstract Co-Author: Nothing to Disclose

Mickael Tanter, Abstract Co-Author: Nothing to Disclose

Michèle Kujas, Abstract Co-Author: Nothing to Disclose

Marc Dhenain PhD, Abstract Co-Author: Nothing to Disclose

Danielle Seilhean MD, Abstract Co-Author: Nothing to Disclose

Andreas Volk PhD, Abstract Co-Author: Nothing to Disclose

Mathias Fink, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

To check the feasibility of non invasive treatment of the brain by using high intensity focused ultrasound through the skull bone. Validation on an animal model with postsonication MRI follow up.

A high power prototype dedicated to trans-skull therapy has been constructed in the Laboratoire Ondes et Acoustique. The array is made of 280 high power transducers working at 1MHz central frequency and is able to reach 400 bars at focus in water during five seconds with a fifty percent duty cycle. An echographic array connected to a Philips HDI 1000 system has been inserted in the therapeutic array in order to perform real time monitoring of the treatment.In a first series of experiments, 10 sheep were treated and sacrificed immediately after treatment. A complete craniotomy has been performed on half of the treated animal models in order to get a reference model. On the other animals, a minimally invasive surgery has been performed thanks to a time reversal experiment: a hydrophone was inserted at the target inside the brain thanks to a 1mm2 craniotomy. A time reversal experiment was then conducted through the skull bone with the therapeutic array to treat the targeted point. In a second series of experiments, 12 animals were divided into three groups and sacrificed respectively one two and three weeks after treatment. The evolution of the targeted region was checked each week thanks to a whole body MRI with T1-weighted contrast enhanced images. Brain were removed and fixed in 10% buffered formalin and imaged with a 4.7T experimental MRI (T2-weighted). Finally, histological examination was performed to confirm tissue damage.

Hyperechogeneicity was clearly visible on the sonographic system during treatment for animals with complete craniotomy. Without craniotomy, the ultrasonic images were too affected to give relevant information. For the first time, necrosis could be achieved non-invasively, by focusing through the skull-bone, as confirmed by MRI imaging and histological examination.

For the first time, ultrasonic brain surgery has been achieved by focusing through the intact skull bone thanks to adaptive focusing based on time reversal technology.

Pernot, M, Aubry, J, Boch, A, Tanter, M, Kujas, M, Dhenain, M, Seilhean, D, Volk, A, Fink, M, et al, , Focused Ultrasound Brain Surgery: In Vivo Investigation on 22 Sheep Using Adaptive Focusing.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4409311.html