Magnetic Resonance-Guided High-Intensity Focused Ultrasound (MR-HIFU): Technical Background and Overview of Current Clinical Applications (Part 1)

Background Extracorporeal high-intensity focused ultrasound (HIFU) is a promising method for the noninvasive thermal ablation of benign and malignant tissue. Current HIFU treatments are performed under ultrasound (US-HIFU) or magnetic resonance (MR-HIFU) image guidance offering integrated therapy planning, real-time control (spatial and temperature guidance) and evaluation. Methods This review is based on publications in peer-reviewed journals addressing thermal ablation using HIFU and includes our own clinical results as well. The technical background of HIFU is explained with an emphasis on MR-HIFU applications. A brief overview of the most commonly performed CE-approved clinical applications for MR-HIFU is given. Results Over the last decade, several HIFU-based applications have received clinical approval in various countries. In particular, MR-HIFU is now approved for the clinical treatment of uterine fibroids, palliation of bone pain, ablation of the prostate and treatment of essential tremor as a first neurological application. Conclusion MR-HIFU is a patient-friendly noninvasive method for thermal ablation which has received clinical approval for several applications. Overall, clinical data demonstrate treatment efficacy, safety and cost efficiency. Key Points: HIFU is a promising technique for noninvasive thermal ablation of tissue. HIFU is typically performed under image guidance using either diagnostic ultrasound (US-HIFU) or MRI (MR-HIFU). The preferred image guidance modality depends on the application. MR guidance offers improved soft-tissue contrast for treatment planning, near real-time and noninvasive temperature monitoring and post-interventional therapy evaluation. MR-HIFU is CE-approved for treatment of uterine fibroids, alleviation of bone pain, prostate tissue ablation and treatment of essential tremor.