Thermal ablation, the most clinically advanced bioeffect of focused ultrasound, produces cell death in a targeted area with minimal damage to the surrounding tissue. 1,2
Tissue damage can be accurately controlled using a range of focused ultrasound transducers with different sonication sizes. Magnetic resonance imaging allows for the monitoring of temperature rise in real time, allowing quantification of the therapeutic dose3.
Alternatively, ultrasound imaging and tissue characterization techniques (e.g. elastography) can be used for treatment monitoring for many clinical applications4. Depending on the equipment and parameters used, the volume of focused ultrasound lesions can be as small as a grain of rice (10 cubic millimeters)2. This allows for an extremely localized treatment and a sharp border between treated and untreated areas.
For treatment of larger structures such as tumors, multiple lesions can be combined to encompass the entire volume2,5. A cooling period between sonications is often required to prevent unwanted heating of surrounding tissue. Therefore, the treatment of very large structures can be time-consuming. However, optimized scanning algorithms, the injection of microbubbles to increase the absorption of acoustic energy, and the use of spiral sonications are all techniques that have been employed to reduce the time of treatments5.
Focused ultrasound’s thermal ablation effect has been the most widely explored clinically, and may be used to non-invasively treat a variety of clinical conditions including symptomatic uterine fibroids6,7; tumors in the prostate, breast, and liver2,8,9; low back pain10; and brain disorders such as essential tremor, Parkinson's disease, and neuropathic pain11-13 among many other conditions.
 Jang HJ, Lee J-Y, Lee D-H, Kim W-H, Hwang JH. Current and Future Clinical Applications of High-Intensity Focused Ultrasound (HIFU) for Pancreatic Cancer. Gut Liver. 2010;4:S57–61.
 Uchida T, Nakano M, Hongo S, Shoji S, Nagata Y, Satoh T, et al. High-intensity focused ultrasound therapy for prostate cancer. Int. J. Urol. Off. J. Jpn. Urol. Assoc. 2012;19:187–201.
 Jolesz FA, Hynynen K, McDannold N, Tempany C. MR imaging-controlled focused ultrasound ablation: a noninvasive image-guided surgery. Magn. Reson. Imaging Clin. N. Am. 2005;13:545–60.
 Song JH, Yoo Y, Song T-K, Chang JH. Real-time monitoring of HIFU treatment using pulse inversion. Phys. Med. Biol. 2013;58:5333–50.
 Park MJ, Kim Y-S, Keserci B, Rhim H, Lim HK. Volumetric MR-guided high-intensity focused ultrasound ablation of uterine fibroids: treatment speed and factors influencing speed. Eur. Radiol. 2013;23:943–50.
 Hesley GK, Gorny KR, Woodrum DA. MR-guided focused ultrasound for the treatment of uterine fibroids. Cardiovasc. Intervent. Radiol. 2013;36:5–13.
 Dobrotwir A, Pun E. Clinical 24 month experience of the first MRgFUS unit for treatment of uterine fibroids in Australia. J. Med. Imaging Radiat. Oncol. 2012;56:409–16.
 Blana A, Walter B, Rogenhofer S, Wieland WF. High-intensity focused ultrasound for the treatment of localized prostate cancer: 5-year experience. Urology. 2004;63:297–300.
 Webb H, Lubner MG, Hinshaw JL. Thermal ablation. Semin. Roentgenol. 2011;46:133–41.
 Weeks EM, Platt MW, Gedroyc W. MRI-guided focused ultrasound (MRgFUS) to treat facet joint osteoarthritis low back pain--case series of an innovative new technique. Eur. Radiol. 2012;22:2822–35.
 Jeanmonod D, Werner B, Morel A, Michels L, Zadicario E, Schiff G, et al. Transcranial magnetic resonance imaging-guided focused ultrasound: noninvasive central lateral thalamotomy for chronic neuropathic pain. Neurosurg. Focus. 2012;32:E1.
 Elias WJ, Huss D, Voss T, Loomba J, Khaled M, Zadicario E, et al. A Pilot Study of Focused Ultrasound Thalamotomy for Essential Tremor. N. Engl. J. Med. 2013;369:640–8.
 Magara A, Bühler R, Moser D, Kowalski M, Pourtehrani P, Jeanmonod D. First experience with MR-guided focused ultrasound in the treatment of Parkinson’s disease. J. Ther. Ultrasound. 2014;2:11.
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