{{short description|Non-invasive therapeutic technique}} {{cs1 config|name-list-style=vanc|display-authors=6}} {{use dmy dates|date=December 2023}} {{Infobox medical intervention | name = High-intensity focused ultrasound | image = Diagram showing liver lesioning using a HIFU transducer 2.png | caption = Diagram showing how HIFU can be used to destroy tissue in the body. An acoustic lens is used to focus sound to a small point in the body. The sound propagates through many layers of tissue. Because of the focal gain, only tissue at the focus is destroyed. | alt = | pronounce = | synonyms = Magnetic-resonance-guided focused ultrasound surgery (MRgFUS), focused ultrasound surgery (FUS), MR-guided focused ultrasound ablation | ICD10 = | ICD9 = | ICD9unlinked = | MeshID = | LOINC = | other_codes = | MedlinePlus = | eMedicine = }}
'''High-intensity focused ultrasound''' ('''HIFU'''), or MR-guided focused ultrasound surgery (MR-guided focused ultrasound ablation), is an incisionless therapeutic technique<ref name="DubinskyCuevas20082">{{cite journal | vauthors = Dubinsky TJ, Cuevas C, Dighe MK, Kolokythas O, Hwang JH | title = High-intensity focused ultrasound: current potential and oncologic applications | journal = AJR. American Journal of Roentgenology | volume = 190 | issue = 1 | pages = 191–199 | date = January 2008 | pmid = 18094311 | doi = 10.2214/AJR.07.2671 }}</ref> that uses non-ionizing ultrasonic waves to heat or ablate tissue. HIFU can be used to increase the flow of blood or lymph or to destroy tissue, such as tumors, via thermal and mechanical mechanisms. Given the prevalence and relatively low cost of ultrasound generation mechanisms, HIFU is expected to be a non-invasive and low-cost therapy that can outperform surgical care.
The technology is different from that used in ultrasonic imaging, though lower frequencies and continuous, rather than pulsed, waves are used to achieve the necessary thermal doses. However, pulsed waves may also be used if mechanical rather than thermal damage is desired. Acoustic lenses are often used to achieve the necessary intensity at the target tissue without damaging the surrounding tissue. The ideal pattern diagram is the beam-focusing of a magnifying glass of sunlight; only the focal point of the magnifying glass has high temperature.
HIFU is combined with other imaging techniques such as medical ultrasound or MRI to guide treatment and monitoring.
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==History== {{more citations needed section|date=April 2016}}
Studies on localized prostate cancer showed that, after treatment, progression-free survival rates were high for low- and intermediate- risk patients with recurrent prostate cancer.<ref>{{cite journal| vauthors = Murat FJ, Poissonier L, Gelet A |date=2007|title=Recurrent Prostate Cancer After Radiotherapy – Salvage Treatment by High-intensity Focused Ultrasound|url=http://www.touchoncology.com/articles/recurrent-prostate-cancer-after-radiotherapy-salvage-treatment-high-intensity-focused-ultra|journal=European Oncological Disease|volume=1|issue=1|pages=60–2|access-date=4 October 2013|archive-date=4 October 2013|archive-url=https://web.archive.org/web/20131004233403/http://www.touchoncology.com/articles/recurrent-prostate-cancer-after-radiotherapy-salvage-treatment-high-intensity-focused-ultra}}</ref>
In March 1992 General Electric filed US patent 5247935 on a system and method combining MRI temperature Imaging with high intensity focused ultrasound.
In 2009, the Insightec ExAblate 2000 was the first MRgFUS system to obtain FDA market approval,<ref name="FDA approval">{{Cite web|url=https://www.fda.gov/medicaldevices/productsandmedicalprocedures/deviceapprovalsandclearances/recently-approveddevices/ucm080704.htm|archive-url=https://web.archive.org/web/20090709234233/http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DeviceApprovalsandClearances/Recently-ApprovedDevices/ucm080704.htm|archive-date=9 July 2009|title=Food and Drug Administration Approval, ExAblate® 2000 System – P040003|website=Food and Drug Administration|date=|access-date=2 December 2023}}</ref>
In 2016, the US Food and Drug Administration (FDA) approved Insightec's Exablate system to treat essential tremor.<ref>FDA News Release. [https://web.archive.org/web/20160712133202/http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm510595.htm "FDA approves first MRI-guided focused ultrasound device to treat essential tremor"], ''FDA'', July 11, 2016</ref> Treatment for other thalamocortical dysrhythmias and psychiatric conditions are under investigation.<ref>{{cite book |author=Martin-Fiori, E |title=Intraoperative Imaging and Image-Guided Therapy |date=2014 |publisher=Springer |isbn=978-1-4614-7657-3 |location=New York |pages=591–599 |chapter=Functional Neurosurgery with MR-Guided HIFU |doi=10.1007/978-1-4614-7657-3_45}}</ref>
In 2023, Edison histotripsy developer Histosonics was approved by the FDA to use the technique to destroy tumors and tissue under real-time image guidance. In 2025 the company closed a $250M investment round.<ref>{{Cite news |date=October 16, 2025 |title=HistoSonics Announces Oversubscribed $250 Million Growth Financing |url=https://www.businesswire.com/news/home/20251016119331/en/HistoSonics-Announces-Oversubscribed-%24250-Million-Growth-Financing?utm_source=tech.therundown.ai&utm_medium=newsletter&utm_campaign=touchscreen-macs-may-finally-arrive&_bhlid=8bf147ca46c277c77175a544a3201d43c1797644}}</ref>
==Medical uses== {{more medical citations needed|section|date=April 2016}} There is no accepted boundary between HIFU and other forms of therapeutic ultrasound. In some literature, HIFU refers to the high levels of energy required to destroy tissue through ablation or cavitation, although it is also sometimes used to describe lower intensity applications such as occupational and physical therapy.
Either way, HIFU is used to non-invasively heat or ablate tissue deep in the body without an incision.<ref name="DubinskyCuevas20082"/> The main applications are the destruction of tissue caused by hyperthermia, increasing perfusion and physical therapy. It later found use to treat tumors of the liver, with clinical trials underway for other sites,<ref>{{Cite web |title=Histotripsy Group |url=https://histotripsy.umich.edu/ |access-date=2025-03-03 |website=Histotripsy Group |language=en-US}}</ref> as well as musculoskeletal conditions.<ref>{{cite journal | vauthors = Robertson VJ, Baker KG | title = A review of therapeutic ultrasound: effectiveness studies | journal = Physical Therapy | volume = 81 | issue = 7 | pages = 1339–1350 | date = July 2001 | pmid = 11444997 | doi = 10.1093/ptj/81.7.1339 | doi-access = free }}</ref>
=== Neurological disorders === thumb|Frontal MRI four days after MRgFUS (MRI-guided high-intensity focused ultrasound): Left ventral intermediate nucleus (Vim) thalamotomy. 79-year-old man with essential tremor. One of the first applications of HIFU was for Parkinson's disease in the 1940s. Although ineffective at the time, HIFU has the capacity to lesion pathology. Focused ultrasound is approved in Israel, Canada, Italy, Korea and Russia to treat essential tremor,<ref>{{cite journal | vauthors = Elias WJ, Huss D, Voss T, Loomba J, Khaled M, Zadicario E, Frysinger RC, Sperling SA, Wylie S, Monteith SJ, Druzgal J, Shah BB, Harrison M, Wintermark M | title = A pilot study of focused ultrasound thalamotomy for essential tremor | journal = The New England Journal of Medicine | volume = 369 | issue = 7 | pages = 640–648 | date = August 2013 | pmid = 23944301 | doi = 10.1056/NEJMoa1300962 | doi-access = free }}</ref> neuropathic pain,<ref>{{cite journal | vauthors = Jeanmonod D, Werner B, Morel A, Michels L, Zadicario E, Schiff G, Martin E | title = Transcranial magnetic resonance imaging-guided focused ultrasound: noninvasive central lateral thalamotomy for chronic neuropathic pain | journal = Neurosurgical Focus | volume = 32 | issue = 1 | pages = E1 | date = January 2012 | pmid = 22208894 | doi = 10.3171/2011.10.FOCUS11248 | s2cid = 2231685 }}</ref> and Parkinsonian tremor.<ref>{{cite journal | vauthors = Magara A, Bühler R, Moser D, Kowalski M, Pourtehrani P, Jeanmonod D | title = First experience with MR-guided focused ultrasound in the treatment of Parkinson's disease | journal = Journal of Therapeutic Ultrasound | volume = 2 | article-number = 11 | year = 2014 | pmid = 25512869 | pmc = 4266014 | doi = 10.1186/2050-5736-2-11 | doi-access = free }}</ref> This approach enables treatment of the brain without an incision or radiation.
=== Cancers === HIFU applied to cancers can disrupt the tumor microenvironment and trigger an immune response, as well as possibly enhance the efficacy of immunotherapy.<ref>{{cite journal |vauthors=Haen SP, Pereira PL, Salih HR, Rammensee HG, Gouttefangeas C |year=2011 |title=More than just tumor destruction: immunomodulation by thermal ablation of cancer |journal=Clinical & Developmental Immunology |volume=2011 |article-number=160250 |doi=10.1155/2011/160250 |pmc=3254009 |pmid=22242035 |doi-access=free}}</ref><ref>{{cite journal |vauthors=Wu F |date=August 2013 |title=High intensity focused ultrasound ablation and antitumor immune response |journal=The Journal of the Acoustical Society of America |volume=134 |issue=2 |pages=1695–1701 |bibcode=2013ASAJ..134.1695W |doi=10.1121/1.4812893 |pmid=23927210}}</ref>
==== Prostate ==== HIFU may be effective for treating prostate cancer.<ref>{{cite journal | vauthors = Chaussy CG, Thüroff S | title = High-Intensity Focused Ultrasound for the Treatment of Prostate Cancer: A Review | journal = Journal of Endourology | volume = 31 | issue = S1 | pages = S30–S37 | date = April 2017 | pmid = 28355119 | doi = 10.1089/end.2016.0548 }}</ref><ref>{{cite journal | vauthors = Hu JC, Laviana A, Sedrakyan A | title = High-Intensity Focused Ultrasound for Prostate Cancer: Novelty or Innovation? | journal = JAMA | volume = 315 | issue = 24 | pages = 2659–2660 | date = June 2016 | pmid = 27367874 | doi = 10.1001/jama.2016.5002 }}</ref><ref>{{cite journal | vauthors = Lepor H, Gold S, Wysock J | title = Focal Ablation of Prostate Cancer | journal = Reviews in Urology | volume = 20 | issue = 4 | pages = 145–157 | date = 2018 | pmid = 30787673 | pmc = 6375006 | doi = 10.3909/riu0809 | doi-broken-date = 1 July 2025 }}</ref>
==== Liver ==== HIFU has been studied in liver cancer and many studies report a high response rate and positive outcome.<ref>{{cite journal | vauthors = Ng KK, Poon RT, Chan SC, Chok KS, Cheung TT, Tung H, Chu F, Tso WK, Yu WC, Lo CM, Fan ST | title = High-intensity focused ultrasound for hepatocellular carcinoma: a single-center experience | journal = Annals of Surgery | volume = 253 | issue = 5 | pages = 981–987 | date = May 2011 | pmid = 21394012 | doi = 10.1097/SLA.0b013e3182128a8b | hdl-access = free | s2cid = 25603451 | hdl = 10722/135541 }}</ref> During the treatment of metastasized liver cancer with HIFU, immune responses have been observed in locations distant from the focal region.<ref>{{cite journal | vauthors = Mauri G, Nicosia L, Xu Z, Di Pietro S, Monfardini L, Bonomo G, Varano GM, Prada F, Della Vigna P, Orsi F | title = Focused ultrasound: tumour ablation and its potential to enhance immunological therapy to cancer | journal = The British Journal of Radiology | volume = 91 | issue = 1083 | article-number = 20170641 | date = February 2018 | pmid = 29168922 | pmc = 5965486 | doi = 10.1259/bjr.20170641 | author3-link = Zhen Xu }}</ref> A 2024 clinical trial of histotripsy on liver tumors, researchers reported a 95% success rate.<ref>{{cite journal | vauthors = Mendiratta-Lala M, Wiggermann P, Pech M, Serres-Créixams X, White SB, Davis C, Ahmed O, Parikh ND, Planert M, Thormann M, Xu Z, Collins Z, Narayanan G, Torzilli G, Cho C, Littler P, Wah TM, Solbiati L, Ziemlewicz TJ | title = The #HOPE4LIVER Single-Arm Pivotal Trial for Histotripsy of Primary and Metastatic Liver Tumors | journal = Radiology | volume = 312 | issue = 3 | article-number = e233051 | date = September 2024 | pmid = 39225612 | pmc = 11427859 | doi = 10.1148/radiol.233051 }}</ref> Clinical trials are underway for treating tumors of the pancreas and kidney.<ref>{{Cite web |title=Evidence |url=https://histosonics.com/resources/evidence/ |access-date=2025-03-03 |website=HistoSonics |language=en-US}}</ref>
=== Histotripsy === Histotripsy is a form of non-thermal HIFU for use on the liver that shows some therapeutic potential.<ref name="SandilosButchyKoneru2024">{{cite journal |vauthors=Sandilos G, Butchy MV, Koneru M, Gongalla S, Sensenig R, Hong YK |date=August 2024 |title=Histotripsy - hype or hope? Review of innovation and future implications |journal=Journal of Gastrointestinal Surgery |volume=28 |issue=8 |pages=1370–1375 |doi=10.1016/j.gassur.2024.05.038 |pmid=38862075}}</ref> Histotripsy mechanically destroys tissue through cavitation.<ref>{{cite journal |vauthors=Xu Z, Hall TL, Vlaisavljevich E, Lee FT |date=2021-01-01 |title=Histotripsy: the first noninvasive, non-ionizing, non-thermal ablation technique based on ultrasound |journal=International Journal of Hyperthermia |volume=38 |issue=1 |pages=561–575 |doi=10.1080/02656736.2021.1905189 |pmc=9404673 |pmid=33827375}}</ref>
=== Kidney stones === Focused ultrasound may be used to dissolve kidney stones by lithotripsy.
=== Cataracts === Ultrasound may be used to treat cataracts by phacoemulsification.
==Mechanism== {{more medical citations needed|section|date=April 2016}} Multiple HIFU beams are precisely focused on a small region of diseased tissue to locally deposit high levels of energy. Focused ultrasound can generate localized heating. Focusing can be guided by Magnetic Resonance Imaging (MRgFUS). These procedures generally use lower frequencies than diagnostic ultrasound (0.7 to 2 MHz), but the higher frequency means lower focusing energy.
===Temperature===
The temperature of tissue at the focus can be increased to between 65 and 85 °C. This induces coagulative necrosis, destroying the tissue. Tissue heated above 60 °C for longer than 1 second becomes irreversibly damaged.<ref>{{cite journal | vauthors = Zhou YF | title = High intensity focused ultrasound in clinical tumor ablation | journal = World Journal of Clinical Oncology | volume = 2 | issue = 1 | pages = 8–27 | date = January 2011 | pmid = 21603311 | pmc = 3095464 | doi = 10.5306/wjco.v2.i1.8 | doi-access = free }}</ref> Each sonication (individual ultrasound energy deposition) treats a precisely defined portion of tissue. Multiple sonications cover a larger area, creating a volume of incompressible material, such as tap water.<ref>{{cite journal | vauthors = Sapareto SA, Dewey WC | title = Thermal dose determination in cancer therapy | journal = International Journal of Radiation Oncology, Biology, Physics | volume = 10 | issue = 6 | pages = 787–800 | date = June 1984 | pmid = 6547421 | doi = 10.1016/0360-3016(84)90379-1 }}</ref>
<math>\mathit{CEM} = \int_{t_o}^{t_f} R^{T_{\mathrm{reference}}-T} dt</math>
with the integral over the treatment time, R=0.5 for temperatures over 43 °C and 0.25 for temperatures between 43 °C and 37 °C, a reference temperature of 43 °C, and time T is in minutes. The equations and methods represent an approach for thermal dose estimation in an incompressible material such as tap water.<ref>{{cite journal | vauthors = Mouratidis PX, Rivens I, Civale J, Symonds-Tayler R, Ter Haar G | title = 'Relationship between thermal dose and cell death for "rapid" ablative and "slow" hyperthermic heating' | journal = International Journal of Hyperthermia | volume = 36 | issue = 1 | pages = 229–243 | date = 2019-01-01 | pmid = 30700171 | doi = 10.1080/02656736.2018.1558289 | doi-access = free }}</ref>
An ultrasound acoustic wave cannot propagate through compressible tissue, such as rubber or human tissues. In that case the ultrasound energy is converted to heat. Using focused beams, a small region of heating can be achieved deep in tissues (usually on the order of 2~3 mm). Tissue changes as a function of the subtle shaking from the heated water within and the duration of this heating according to the thermal dose metric. Focusing at more than one place or by scanning, a volume can be ablated.<ref>{{cite journal | vauthors = Huisman M, Lam MK, Bartels LW, Nijenhuis RJ, Moonen CT, Knuttel FM, Verkooijen HM, van Vulpen M, van den Bosch MA | title = Feasibility of volumetric MRI-guided high intensity focused ultrasound (MR-HIFU) for painful bone metastases | journal = Journal of Therapeutic Ultrasound | volume = 2 | page = 16 | year = 2014 | pmid = 25309743 | pmc = 4193684 | doi = 10.1186/2050-5736-2-16 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Köhler MO, Mougenot C, Quesson B, Enholm J, Le Bail B, Laurent C, Moonen CT, Ehnholm GJ | title = Volumetric HIFU ablation under 3D guidance of rapid MRI thermometry | journal = Medical Physics | volume = 36 | issue = 8 | pages = 3521–3535 | date = August 2009 | pmid = 19746786 | doi = 10.1118/1.3152112 | bibcode = 2009MedPh..36.3521K }}</ref><ref>{{cite journal | vauthors = Monteith SJ, Kassell NF, Goren O, Harnof S | title = Transcranial MR-guided focused ultrasound sonothrombolysis in the treatment of intracerebral hemorrhage | journal = Neurosurgical Focus | volume = 34 | issue = 5 | pages = E14 | date = May 2013 | pmid = 23634918 | doi = 10.3171/2013.2.FOCUS1313 | doi-access = free }}</ref> Thermal doses of 120-240 min at 43 °C coagulate cellular protein and lead to irreversible tissue destruction.
===Cavitation===
==== Inertial ==== At high enough acoustic intensities, cavitation (microbubbles forming and interacting with the ultrasound field) can occur. Microbubbles produced in the field oscillate and grow (due to factors including rectified diffusion), and can eventually implode (inertial or transient cavitation). During inertial cavitation, temperatures increase inside the bubbles. The ultimate collapse during the rarefaction phase is associated with a shock wave and jets that can mechanically damage tissue.<ref>{{cite book| vauthors = Leighton TG |title=Ultrasound in food processing|date=1997|publisher=Thomson Science, London, Blackie Academic and Professional| chapter = Chapter 9: The principles of cavitation|pages=151–182}}</ref>
==== Stable ==== Stable cavitation creates microstreaming, which induces high shear forces on cells and leads to apoptosis. Bubbles produced by the vaporization of water due to acoustic forces oscillate under a low-pressure acoustic field. Strong streaming may cause cell damage, but also reduces tissue temperature via convective heat loss.<ref>{{cite journal | vauthors = Levario-Diaz V, Bhaskar P, Carmen Galan M, Barnes AC | title = Effect of acoustic standing waves on cellular viability and metabolic activity | journal = Scientific Reports | volume = 10 | issue = 1 | article-number = 8493 | date = May 2020 | pmid = 32444830 | pmc = 7244593 | doi = 10.1038/s41598-020-65241-4 | bibcode = 2020NatSR..10.8493L | doi-access = free | author-link3 = M. Carmen Galan }}</ref>
===Theory===
Ultrasound can be focused in several ways—via a lens (for example, a polystyrene lens, parabola curve transducer, or a phased array). This can be calculated using an exponential model of ultrasound attenuation. The ultrasound intensity profile is bounded by an exponentially decreasing function where the decrease in ultrasound is a function of distance traveled through tissue:
<math> I=I_o {e}^{-2\alpha \mathrm{z}}</math>
<math>I_o</math> is the initial intensity of the beam, <math>\alpha</math> is the attenuation coefficient (in units of inverse length), and z is the distance traveled through the attenuating medium (e.g. tissue).
In this ideal model, <math>\frac{-\partial I}{\partial \mathrm{z}} = 2\alpha I= Q</math><ref>{{cite journal | vauthors = Hariharan P, Myers MR, Banerjee RK | title = HIFU procedures at moderate intensities--effect of large blood vessels | journal = Physics in Medicine and Biology | volume = 52 | issue = 12 | pages = 3493–3513 | date = June 2007 | pmid = 17664556 | doi = 10.1088/0031-9155/52/12/011 | s2cid = 26124121 | bibcode = 2007PMB....52.3493H }}</ref> is a measure of the power density of the heat absorbed from the ultrasound field. This demonstrates that tissue heating is proportional to intensity, and that intensity is inversely proportional to the area over which an ultrasound beam is spread. Therefore, narrowly focusing the beam or increasing the beam intensity creates a rapid temperature rise at the focus.{{citation needed|date=April 2016}}
The ultrasound beam can be focused in several ways: *Geometrically, with a lens or with a spherically curved transducer. *Electronically, by adjusting the relative phases of elements in an array of transducers (a "phased array"). This steers the beam to different locations. Aberrations in the ultrasound beam due to tissue structures can be corrected.{{citation needed|date=April 2016}} This assumes no reflection, no absorption and no diffusion in intermediate tissue. The ultrasound itself can penetrate incompressible materials such as water, but compressible materials such as air, rubber, human tissue, fat, fiber, hollow bone, and fascia reflect, absorb, and diffuse the energy.
==Beam delivery== Beam delivery consists of beam steering and image guidance. The beam has the ability to pass through overlying tissues without harm and focus on a localized area of 2–3 mm (at most), that determines the frequency of the ultrasound. Following ablation a distinct boundary (less than 50 microns wide) forms between healthy and necrotic tissue.<ref name="Izadifar_2020">{{cite journal | vauthors = Izadifar Z, Izadifar Z, Chapman D, Babyn P | title = An Introduction to High Intensity Focused Ultrasound: Systematic Review on Principles, Devices, and Clinical Applications | journal = Journal of Clinical Medicine | volume = 9 | issue = 2 | page = 460 | date = February 2020 | pmid = 32046072 | pmc = 7073974 | doi = 10.3390/jcm9020460 | doi-access = free }}</ref>
=== Beam steering === The most common transducer is a concave focusing transducer with a fixed aperture and a fixed focal length.<ref name="Izadifar_2020" /> Phased array transducers can be used with different arrangements (flat/bowl).<ref name="Izadifar_2020"/>
=== Beam guidance === HIFU therapy requires careful monitoring and so it is usually performed in conjunction with other imaging techniques.
Pre-operative imaging, for instance CT and MRI, are used to identify general parameters of the target anatomy. Real-time imaging provides safe and accurate noninvasive targeting and monitoring. Both MRI and medical ultrasound have been used. These techniques are known respectively as Magnetic Resonance guided Focused Ultrasound Surgery (MRgFUS)<ref>{{cite journal | vauthors = Kotopoulis S, Wang H, Cochran S, Postema M | title = Lithium niobate transducers for MRI-guided ultrasonic microsurgery | journal = IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | volume = 58 | issue = 8 | pages = 1570–1576 | date = August 2011 | pmid = 21859576 | doi = 10.1109/TUFFC.2011.1984 | bibcode = 2011ITUFF..58.1570K | s2cid = 11382728 | url = https://hal.archives-ouvertes.fr/hal-03193255/file/Revised%20Document_Lithium%20niobate%20transducers%20for%20MRI-guided%20ultrasonic%20microsurgery.pdf }}</ref><ref name="MedelMonteith2012">{{cite journal | vauthors = Medel R, Monteith SJ, Elias WJ, Eames M, Snell J, Sheehan JP, Wintermark M, Jolesz FA, Kassell NF | title = Magnetic resonance-guided focused ultrasound surgery: Part 2: A review of current and future applications | journal = Neurosurgery | volume = 71 | issue = 4 | pages = 755–763 | date = October 2012 | pmid = 22791029 | pmc = 4104674 | doi = 10.1227/NEU.0b013e3182672ac9 }}</ref> and Ultrasound guided Focused Ultrasound Surgery (USgFUS) respectively.<ref name="DubinskyCuevas20082"/><ref name="Belzberg2020">{{cite journal | vauthors = Belzberg M, Mahapatra S, Perdomo-Pantoja A, Chavez F, Morrison K, Xiong KT, Gamo NJ, Restaino S, Thakor N, Yazdi Y, Iyer R, Tyler B, Theodore N, Luciano MG, Brem H, Groves M, Cohen AR, Manbachi A | title = Minimally invasive therapeutic ultrasound: Ultrasound-guided ultrasound ablation in neuro-oncology | journal = Ultrasonics | volume = 108 | issue = 12 | article-number = 106210 | date = December 2020 | pmid = 32619834 | pmc = 8895244 | doi = 10.1016/j.ultras.2020.106210 | doi-access = free }}</ref>
MRgFUS is a 3D imaging technique. It features high soft tissue contrast and provides information about temperature, thus allowing ablation to be monitored. However, low frame rates make this technique perform poorly in real-time imaging while high costs limit its use.<ref name="CafarelliMura2015">{{cite conference <!-- Citation bot no --> | vauthors = Cafarelli A, Mura M, Diodato A, Schiappacasse A, Santoro M, Ciuti G, Menciassi A |title= 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) |chapter=A computer-assisted robotic platform for Focused Ultrasound Surgery: Assessment of high intensity focused ultrasound delivery |date=25–29 August 2015 |pages=1311–1314 |doi=10.1109/EMBC.2015.7318609 |pmid=26736509 |isbn=978-1-4244-9271-8 |s2cid=4194253}}</ref>
USgFUS is a 2D imaging technique. While no quantitative temperature measurement system is available, benefits such as high frame rate (up to 1000 images per second), low cost and minimal adverse health effects commend it. Ultrasound verifies the acoustic window in real time using the same modality as the therapy.<ref name="Chen_2017">{{cite journal | vauthors = Chen PH, Hsieh KS, Huang CC | title = An Acoustic Tracking Approach for Medical Ultrasound Image Simulator | journal = Journal of Medical and Biological Engineering | volume = 37 | issue = 6 | pages = 944–952 | date = 2017 | pmid = 30416414 | pmc = 6208925 | doi = 10.1007/s40846-017-0258-9 }}</ref> This implies that if the target region is not visualized by ultrasound imaging before and during therapy, then it is unlikely that the therapy will be effective in that specific region.<ref name="Chen_2017" /> In addition, treatment outcomes can be estimated in real time through visual inspection of hyperechoic changes in standard B-mode images.<ref name="EbbiniTer Haar2015">{{cite journal | vauthors = Ebbini ES, ter Haar G | title = Ultrasound-guided therapeutic focused ultrasound: current status and future directions | journal = International Journal of Hyperthermia | volume = 31 | issue = 2 | pages = 77–89 | date = March 2015 | pmid = 25614047 | doi = 10.3109/02656736.2014.995238 | s2cid = 23590340 | doi-access = free }}</ref>
== References == {{reflist|32em}}
{{DEFAULTSORT:High Intensity Focused Ultrasound}} Category:Medical ultrasonography Category:Magnetic resonance imaging Category:Medical physics