MR monitoring of focused ultrasound surgery in a breast tissue model in vivo

The objective of this study was to investigate MRI methods for monitoring f ocused ultrasound surgery (FUS) of breast tumors. To this end, the mammary glands of sheep were used as tissue model. The tissue was treated in vivo w ith numerous single sonications which covered extended target volumes by em ploying a scanning technique. The ultrasound focus position was controlled by online temperature mapping based on the temperature dependence of the re laxation time T-1. This approach proved to be reliable and offers thus an a lternative to proton resonance frequency methods, whose application is hamp ered in fatty tissues. FUS-induced tissue changes were visible on T-2- as w ell as on pre- and post-contrast T-1-weighted images. According to our init ial experience, noninvasive MRI-guided FUS of breast tumors is feasible. (C ) 2001 Elsevier Science Inc. All rights reserved.