Session: 1J

Purpose: To test a prototype Magnetic Resonance Imaging (MRI) compatible focused ultrasound phased array system for trans-skull brain tissue ablation using ex vivo human skulls and an animal model. Methods: Rabbit thigh muscle (N=3) and brain (N=10) were sonicated with a prototype, hemispherical 500element ultrasound phased array operating at frequencies between 700 and 800 kHz. An ex vivo human skull sample was placed between the array and the animal tissue. The temperature elevation during 20-30 s sonications were monitored using MRI thermometry. The induced focal lesions were observed in T2 and contrast-enhanced T1-weighted Fast Spin Echo images. Whole brain histology evaluation was performed after the sonications. Results: Sharp temperature elevations were produced both in the thigh muscle and in the brain. The temperature elevations per applied acoustic watt during 20 s sonications in the thigh muscle and brain were 0.04+/0.03C and 0.022 +/0.010C, respectively. The high power sonications (600 1080 W) produced peak temperature up to 55C and focal lesions that were consistent with thermal tissue damage. The lesion size was found to increase with increasing peak temperature Conclusions: This study demonstrates that it is possible to create ultrasound-induced lesions in vivo through a human skull under MRI guidance with this large-scale phased array device.