MRI controlled HIFU treatment of breast tissue

It was the objective of this study to test the feasibility of MRI (Magnetic Resonance Imaging)-monitored focused ultrasound surgery (FUS or HIFU: High Intensity Focused Ultrasound) for the treatment of breast glandular tissue in animals. The authors treated 15 "L"-shaped target volumes in the sheep breast applying 30 to 128 ultrasound pulses at a frequency of 1.7 MHz and an electrical power of 25-75 W per pulse. Therapy was performed with a newly designed fully MRI compatible ultrasound therapy unit. By means of a MRI T1w (T1-weighted) TurboFLASH sequence positions of the ultrasound foci could clearly be detected. Conventional T1w and T2w MR imaging was carried out for assessing therapy effects. After treatments the animals were sacrificed and a histologic workout was preceded. Planning the target volume in MR images, application of ultrasound and temperature monitoring by T1w MRI were feasible in the authors' experimental setup. Ultrasound foci could be localized by MR thermometry. Lesions induced were detectable in T2w MR imaging and post contrast T1w sequences. The histologic workout displayed coagulative necroses in the treated tissue areas, fibrosis was present in long-term evaluations. Treatment with the authors' specially designed and constructed MR compatible FUS unit was feasible in breast tissue, therapeutic effects could be proved in both, radiologic imaging and histology.