Principles of focused ultrasound.

Focused ultrasound (FUS/HIFU) relies on ablation of pathological tissues by delivering a sufficiently high level of acoustic energy in situ of the human body. Magnetic Resonance guided FUS (MRgFUS/HIFU) and Ultrasound guided (USgFUS/HIFU) are image guided techniques combined with therapeutic FUS for monitoring purposes. The principles and technologies of FUS/HiFU are described in this paper including the basics of MR guidance techniques and MR temperature mapping. Clinical applications of FUS/HIFU gained CE and FDA approvals for the treatment of various benign and few malignant lesions in the last two decades. Current technical limitations of ultrasound guided and MRI guided Focused Ultrasound, as well as adverse effects for the application of this technique are outlined including challenges of ablating moving organs (liver and kidney). An outlook to possible applications is provided; exampling clinical trials discussing future options.