High intensity focused ultrasound
Encyclopedia
High-Intensity Focused Ultrasound (HIFU, or sometimes FUS) is a highly precise medical procedure using high-intensity focused ultrasound
to heat and destroy pathogenic
tissue
rapidly through ablation
. It is one modality of therapeutic ultrasound, and, although it induces hyperthermia, it should not be confused with this technique, which heats much less rapidly and to much lower therapeutic temperatures (in general < 45°C), although some hyperthermia treatments are ablative.
Clinical HIFU procedures are typically image-guided to permit treatment planning and targeting before applying a therapeutic or ablative level of ultrasound energy. When MRI is used for guidance, the technique is sometimes called Magnetic Resonance-guided Focused Ultrasound, often shortened to MRgHIFU or MRgFUS. When ultrasonography is used, the technique is sometimes called Ultrasound-guided Focused Ultrasound, often shortened to USgFUS. Magnetic resonance imaging
(MRI) is used to identify tumors or fibroids in the body, before they are destroyed by the ultrasound. MRgFUS is currently used in Australia, the United States, Canada, Israel, Europe, and Asia to treat uterine fibroids
. Ultrasonography guided HIFU is currently used in the United Kingdom, Italy, Spain, Korea, Japan, Hong Kong, Malaysia, Russia, China, Romania, Mexico and Bulgaria. Current clinical trials are underway, examining the possible use of HIFU in the treatment of cancers of the brain, breast, liver, bone, and prostate.
Therapeutic ultrasound is a minimally invasive or non-invasive method to deposit acoustic energy into tissue. Applications include tissue ablation
(HIFU) (for tumor
treatments, for example), hyperthermia
treatments (low-level heating combined with radiation or chemotherapy), or the activation or enhanced delivery of drug
s.
where
is the initial beam intensity, 
is the attenuation coefficient in units of inverse length, and z is the distance traveled through the attenuating medium.
In this model,
is a measure of the power density of the heat absorbed from the ultrasound field. Sometimes, SAR is also used to express the amount of heat absorbed by a specific medium and is related to Q by dividing Q by the tissue density. Also, this demonstrates that tissue heating is proportional to the intensity and the intensity is proportional to the area over which an ultrasound beam is spread, which is why focusing the beam into a sharp point (i.e. increasing the beam intensity) creates a rapid temperature rise at the focus.
The amount of damage caused in the tissue can be modeled using Cumulative Equivalent Minutes (CEM). Several formulations of the CEM equation have been suggested over the years, but the equation currently in use for most research done in HIFU therapy comes from a 1984 paper by Dewey and Sapareto:
with the integral being over the treatment time, R=2 for temperatures over 43°C and 4 for temperatures between 43°C and 37°C, a reference temperature of 43°C, and time in minutes. This formula is an empirical formula.
(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, very high temperatures inside the bubbles occur, and the collapse is associated with a shock wave
and jets that can mechanically damage tissue. Because the onset of cavitation and the resulting tissue damage can be unpredictable, it has generally been avoided in clinical applications. However, cavitation
is currently being investigated as a means to enhance HIFU ablation and for other applications.
of the beams theoretically treats a precisely defined portion of the targeted tissue, although in practice cold spots (cause by, among other things, blood perfusion in the tissue), beam distortion, and beam mis-registration are impediments to finely controlled treatments. The entire therapeutic target is treated by moving the applicator on its robotic arm in order to juxtapose multiple shots, according to a protocol designed by the physician. This technology can achieve precise ablation
of diseased tissue, therefore is sometimes called HIFU surgery. Because it destroys the diseased tissue non-invasively, it is also known as "Non-invasive HIFU surgery". Anesthesia is not required, but should be recommended. The treatment can be combined with radiotherapy or chemotherapy.
. HIFU treatment for uterine fibroids was approved by the Food and Drug Administration
(FDA) in October 2004. This is a non-invasive treatment option for patients suffering from symptomatic fibroids. Most patients benefit from HIFU and symptomatic relief is sustained for two plus years. Up to 16-20% of patient will require an additional treatment.
Currently available approved uterine fibroids HIFU treatment devices are Philips Sonalleve MR-HIFU
and GE Insightec ExAblate
2000 and ExAblate 2100. Additionally, Haifu models JC and JC200 have CE approval.
During HIFU, the entire prostate is ablated, including the prostatic urethra
. The urethra has regenerative ability because it is derived from a different type of tissue (bladder squamous-type epithelium
) rather than prostatic tissue (glandular, fibrotic and muscular). While the urethra is an important anatomical structure, the sphincter
and bladder neck are more important to maintaining the urinary function. During HIFU the sphincter and bladder neck are identified and avoided.
Developed in 1989 in France with Inserm (French National Institute of Medical Research), Edouard Herriot Hospital in Lyon and EDAP TMS (Nasdaq : EDAP), Ablatherm HIFU was the first prostate cancer HIFU device to receive CE marking in 2000. The first "Ablathermy" treatments on men were performed in 1993 and as of January, 2010, more than 21,000 treatments have been performed worldwide.
Developed in the early 1990s for the treatment of benign prostate hyperplasia (BPH) in the US by Misonix (Nasdaq: MSON), Sonablate was then modified to treat prostate cancer at the end of the 1990s. Sonablate 500 received CE marking in 2001. As of January 2010, a total of more than 9,000 treatments have been performed for benign prostate hyperplasia and over 7,000 prostate cancer treatments.
During Sonablate HIFU, the physician obtains real-time ultrasound images of the prostate and surrounding areas. From these images, a customized plan for delivering the ultrasound energy is created. The Sonablate software allows the physician to precisely define the treatment zones in order to destroy the entire gland.
Sonablate HIFU is minimally invasive, performed on an outpatient basis and typically lasts 2–4 hours, depending on the size of the prostate. There is no surgery or radiation involved. Patients wear a catheter post-procedure but are able to resume normal activities almost immediately. The Sonablate is the only HIFU device for prostate cancer that does not require an advance surgical procedure (known as a TURP) in order to achieve effective results when treating enlarged prostate glands. Sonablate HIFU can treat large prostates up to 40 grams.
The Sonablate incorporates three-dimensional imaging to provide better visuals of the prostate, especially any irregularities, and allow the physician to create the most effective treatment plan possible. The newest technological enhancement to the Sonablate is tissue change monitoring (TCM) software, which gives real-time feedback to the physician, thus confirming if sufficient energy has been delivered to completely ablate the tissue.
to destroy solid tumors of the bone, brain, breast, liver, pancreas, rectum, kidney, testes, prostate. At this stage, cancer treatments are still in the investigatory phases as there is a need to find more about their effectiveness.
HIFU has been found to offer palliative care. CE approval has been given for palliative treatment of bone metastasis. Experimentally, a palliative effect was found in cases of advanced pancreatic cancer.
HIFU may be used to create high temperatures not necessarily to treat the cancer alone, but in conjunction with targeted delivery of cancer drugs. For example, HIFU and other devices may be used to activate temperature-sensitive liposomes, filled with cancer drug "cargo" to release the drug in high concentrations only at the tumor site(s) only where triggered to do so by the hyperthermia device (See Hyperthermia therapy
). This novel approach is resulting in drug concentrations 10 times or more than traditional chemo with a fraction of the side effects since the drug is not released system-wide.
In addition, several thousand patients with different types of tumors have been treated in China with HIFU using ultrasound imaging-guided devices built by several different companies.
, allowing absorption of drugs into the brain. It is most effective when used in combination with a calcium channel blocker
like verapamil
.
(AF). A minimally invasive catheter based system designed to ablate heart tissue responsible for propagating AF has been approved for use in Europe and is undergoing an FDA approved phase III pivotal efficacy trial in the United States.
The first commercial HIFU machine, called the Sonablate 200, was developed by the American company Focus Surgery, Inc. (Milipitas, CA) and launched in Europe in 1994 after receiving CE approval, bringing a first medical validation of the technology for benign prostatic hyperplasia (BPH). Comprehensive studies by practitioners at more than one site using the device demonstrated clinical efficacy for the destruction of prostatic tissue without bloodloss or long term side effects. Later studies on localized prostate cancer by Murat and colleagues at the Edouard Herriot Hospital in Lyon in 2006 showed that after treatment with the Ablatherm (EDAP TMS, Lyon, France), progression-free survival rates are very high for low- and intermediate- risk patients with recurrent prostate cancer (70% and 50% respectively) HIFU treatment of prostate cancer is currently an approved therapy in Europe, Canada, South Korea, Australia, and elsewhere. Clinical trials in the United States
are expected to begin in 2006. Prostate cancer trials for the new Sonablate 500 are ongoing in the U.S.A. currently.
Magnetic Resonance Guided Focused Ultrasound MRgFUS was first cited in the article "On-line MRI monitored noninvasive ultrasound" by Hynynen K., Damianou C., Darkazanli A., Unger E., Levy M., SchencK J. in Proceedings of the annual international conference of the IEEE engineering in medicine and biology society,October 1992. Cline HE, Schenck JF, Hynynen K, Watkins RD, Souza SP, Jolesz FA Journal of Computer Assisted Tomography [1992, 16(6):956-65] was published nearly the same time. U.S. Patent #5247935. was Filed March 19,1992 The technology was later transferred to InsighTec in Haifa Israel in 1998. The InsighTec ExAblate 2000 was the first MR Guided focused ultrasound system to obtain FDA market approval in the United States.
Haifu Model JC and JC200 by ChongQing Haifu Ltd. are complete ultrasound guided tumor treatment systems, and they were CE approved in 2005 for benign and malignant tumors.
HIFU-2001(By Sumo Corporation Ltd) is an enhanced technology treatment system that does not require anesthesia. Since 2001 it has been used in Asian countries to treat Liver/Pancreas/Bladder/Uterus/Kidney.
An important difference between HIFU and many other forms of focused energy, such as radiation therapy or radio surgery, is that the passage of ultrasound energy through intervening tissue has no apparent cumulative effect on that tissue.
The absence of cumulative effect of HIFU on the treated tissue means that the treatment can be repeated in case of first HIFU treatment failure or partial treatment of the prostate. As a clean treatment (= non-ionizing) HIFU is also an option to treat prostate cancer recurrence after radiation therapy failure.
The University of Minnesota produced a dual-mode ultrasound transducer that offers time resolution measured in milliseconds and offers closed-loop, real-time, intensity modulation based on continuous monitoring of tissue response to the HIFU beam. This method offers improved resolution over MRI.
Clinically, MRI-guided HIFU treatments have been tested for uterine fibroids, breast fibroadenomas, breast cancer, bone metastases, and liver tumors. The largest number of patients treated with MRI-guided HIFU have been with uterine fibroids.
USgFUS treatments have been approved with CE for wider range of benign and malignant tumors due to its higher power, precision and realtime monitoring system. The largest number of patients are uterine fibroids.
Ultrasound-guided HIFU treatments have been approved in Europe and Asia. MRI-guided treatments of uterine fibroids have been approved in Europe and Asia, and were granted FDA approval in the US in 2004.
The Foundation for Focused Ultrasound Research
is an unincorporated association promoting research into medical uses of high intensity focused ultrasound, including HIFU.
The Focused Ultrasound Surgery Foundation
(FUSF) is working to shorten the time from technology development to patient treatment, develop new applications and accelerate the worldwide adoption of MR-guided focused ultrasound surgery
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
to heat and destroy pathogenic
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
rapidly through ablation
Ablation
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
. It is one modality of therapeutic ultrasound, and, although it induces hyperthermia, it should not be confused with this technique, which heats much less rapidly and to much lower therapeutic temperatures (in general < 45°C), although some hyperthermia treatments are ablative.
Clinical HIFU procedures are typically image-guided to permit treatment planning and targeting before applying a therapeutic or ablative level of ultrasound energy. When MRI is used for guidance, the technique is sometimes called Magnetic Resonance-guided Focused Ultrasound, often shortened to MRgHIFU or MRgFUS. When ultrasonography is used, the technique is sometimes called Ultrasound-guided Focused Ultrasound, often shortened to USgFUS. Magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI) is used to identify tumors or fibroids in the body, before they are destroyed by the ultrasound. MRgFUS is currently used in Australia, the United States, Canada, Israel, Europe, and Asia to treat uterine fibroids
Uterine fibroids
A uterine fibroid is a benign tumor that originates from the smooth muscle layer and the accompanying connective tissue of the uterus.Fibroids are the most common benign tumors in...
. Ultrasonography guided HIFU is currently used in the United Kingdom, Italy, Spain, Korea, Japan, Hong Kong, Malaysia, Russia, China, Romania, Mexico and Bulgaria. Current clinical trials are underway, examining the possible use of HIFU in the treatment of cancers of the brain, breast, liver, bone, and prostate.
Therapeutic ultrasound is a minimally invasive or non-invasive method to deposit acoustic energy into tissue. Applications include tissue ablation
Ablation
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
(HIFU) (for tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
treatments, for example), hyperthermia
Hyperthermia
Hyperthermia is an elevated body temperature due to failed thermoregulation. Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate...
treatments (low-level heating combined with radiation or chemotherapy), or the activation or enhanced delivery of drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
s.
Theory
Ultrasound can be focused, either via a lens (for example, a polystyrene lens), a curved transducer, or a phased array (or any combination of the three) into a small focal zone, in a similar way to focusing light through a magnifying glass focusing light rays to a point. Using an exponential model of ultrasound attenuation (i.e. the ultrasound intensity profile is bounded by an exponentially decreasing function where the decrease in ultrasound is a function of the distance traveled through the tissue), this can be modeled aswhere
is the initial beam intensity, is the attenuation coefficient in units of inverse length, and z is the distance traveled through the attenuating medium.In this model,
is a measure of the power density of the heat absorbed from the ultrasound field. Sometimes, SAR is also used to express the amount of heat absorbed by a specific medium and is related to Q by dividing Q by the tissue density. Also, this demonstrates that tissue heating is proportional to the intensity and the intensity is proportional to the area over which an ultrasound beam is spread, which is why focusing the beam into a sharp point (i.e. increasing the beam intensity) creates a rapid temperature rise at the focus.The amount of damage caused in the tissue can be modeled using Cumulative Equivalent Minutes (CEM). Several formulations of the CEM equation have been suggested over the years, but the equation currently in use for most research done in HIFU therapy comes from a 1984 paper by Dewey and Sapareto:
with the integral being over the treatment time, R=2 for temperatures over 43°C and 4 for temperatures between 43°C and 37°C, a reference temperature of 43°C, and time in minutes. This formula is an empirical formula.
Focusing
The ultrasound beam can be focused in these ways:- Geometrically, for example with a lensLens (optics)A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
or with a spherically curved transducerTransducerA transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...
. - Electronically, by adjusting the relative phases of elements in an array of transducers (a "phased arrayPhased arrayIn wave theory, a phased array is an array of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.An antenna array...
"). By dynamically adjusting the electronic signals to the elements of a phased array, the beam can be steered to different locations, and aberrations in the ultrasound beam due to tissue structures can be corrected.
How HIFU works
As an acoustic wave propagates through the tissue, part of it is absorbed and converted to heat. With focused beams, a very small focus can be achieved deep in tissues (usually on the order of milimeters, with the beam having a characteristic "cigar" shape in the focal zone, where the beam is longer than it is wide along the transducer axis). Tissue damage occurs as a function of both the temperature to which the tissue is heated and how long the tissue is exposed to this heat level in a metric referred to as "thermal dose". By focusing at more than one place or by scanning the focus, a volume can be thermally ablated. At high enough acoustic intensities, cavitationCavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
(microbubbles
Microbubbles
Microbubbles are bubbles smaller than one millimetre in diameter, but larger than one micrometre. They are used in medical diagnostics as a contrast agent for ultrasound imaging....
forming and interacting with the ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
field) can occur. Microbubbles produced in the field oscillate and grow (due to factors including rectified diffusion
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
), and can eventually implode (inertial or transient cavitation). During inertial cavitation, very high temperatures inside the bubbles occur, and the collapse is associated with a shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
and jets that can mechanically damage tissue. Because the onset of cavitation and the resulting tissue damage can be unpredictable, it has generally been avoided in clinical applications. However, cavitation
Cavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
is currently being investigated as a means to enhance HIFU ablation and for other applications.
Method of use
In HIFU therapy, ultrasound beams are focused on diseased tissue, and due to the significant energy deposition at the focus, temperature within the tissue can rise to levels from 65° to 85°C, destroying the diseased tissue by coagulation necrosis. Higher temperature levels are typically avoided to prevent boiling of liquids inside the tissue. Each sonicationSonication
thumb|right|A sonicator at the [[Weizmann Institute of Science]] during sonicationSonication is the act of applying sound energy to agitate particles in a sample, for various purposes. In the laboratory, it is usually applied using an ultrasonic bath or an ultrasonic probe, colloquially known as...
of the beams theoretically treats a precisely defined portion of the targeted tissue, although in practice cold spots (cause by, among other things, blood perfusion in the tissue), beam distortion, and beam mis-registration are impediments to finely controlled treatments. The entire therapeutic target is treated by moving the applicator on its robotic arm in order to juxtapose multiple shots, according to a protocol designed by the physician. This technology can achieve precise ablation
Ablation
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
of diseased tissue, therefore is sometimes called HIFU surgery. Because it destroys the diseased tissue non-invasively, it is also known as "Non-invasive HIFU surgery". Anesthesia is not required, but should be recommended. The treatment can be combined with radiotherapy or chemotherapy.
Uterine fibroids
Development of this therapy significantly broadened the range of treatment options for patients suffering from uterine fibroidsUterine fibroids
A uterine fibroid is a benign tumor that originates from the smooth muscle layer and the accompanying connective tissue of the uterus.Fibroids are the most common benign tumors in...
. HIFU treatment for uterine fibroids was approved by the Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
(FDA) in October 2004. This is a non-invasive treatment option for patients suffering from symptomatic fibroids. Most patients benefit from HIFU and symptomatic relief is sustained for two plus years. Up to 16-20% of patient will require an additional treatment.
Currently available approved uterine fibroids HIFU treatment devices are Philips Sonalleve MR-HIFU
Sonalleve MR-HIFU
Sonalleve MR-HIFU is a medical system developed by Philips Healthcare for the treatment of uterine fibroids without surgery . The system is using non-invasive High Intensity Focused Ultrasound technology guided by Magnetic Resonance . Hence the acronym MR-HIFU...
and GE Insightec ExAblate
ExAblate
The ExAblate is a non-invasive medical device manufactured by InSightec, a company based in Haifa, Israel with its US office in Dallas, TX. The ExAblate uses MRI guided Focused Ultrasound Surgery technology, which combines magnetic resonance imaging with focused ultrasound...
2000 and ExAblate 2100. Additionally, Haifu models JC and JC200 have CE approval.
Prostate cancer
The earliest widespread use of HIFU ablation was as a treatment for prostate cancer. This treatment is administered through a trans-rectal probe and relies on heat developed by focusing ultrasound waves into the prostate to kill the tumor. Promising results approaching those of surgery have been reported in large series of prostate cancer patients. These treatments are performed under ultrasound imaging guidance, which allows for treatment planning and some minimal indication of the energy deposition. HIFU may also be used to ablate the entire prostate gland using a transrectal probe. This is an outpatient procedure that usually last 1–3 hours. Results show that it greatly reduces some of the side effects common with other treatments for prostate cancer.During HIFU, the entire prostate is ablated, including the prostatic urethra
Prostatic urethra
The prostatic urethra, the widest and most dilatable part of the urethra canal, is about 3 cm. long.It runs almost vertically through the prostate from its base to its apex, lying nearer its anterior than its posterior surface; the form of the canal is spindle-shaped, being wider in the middle...
. The urethra has regenerative ability because it is derived from a different type of tissue (bladder squamous-type epithelium
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
) rather than prostatic tissue (glandular, fibrotic and muscular). While the urethra is an important anatomical structure, the sphincter
Sphincter
A sphincter is an anatomical structure, or a circular muscle, that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning...
and bladder neck are more important to maintaining the urinary function. During HIFU the sphincter and bladder neck are identified and avoided.
Ablatherm Robotic HIFU
Developed in 1989 in France with Inserm (French National Institute of Medical Research), Edouard Herriot Hospital in Lyon and EDAP TMS (Nasdaq : EDAP), Ablatherm HIFU was the first prostate cancer HIFU device to receive CE marking in 2000. The first "Ablathermy" treatments on men were performed in 1993 and as of January, 2010, more than 21,000 treatments have been performed worldwide.
Sonablate 500
Developed in the early 1990s for the treatment of benign prostate hyperplasia (BPH) in the US by Misonix (Nasdaq: MSON), Sonablate was then modified to treat prostate cancer at the end of the 1990s. Sonablate 500 received CE marking in 2001. As of January 2010, a total of more than 9,000 treatments have been performed for benign prostate hyperplasia and over 7,000 prostate cancer treatments.
During Sonablate HIFU, the physician obtains real-time ultrasound images of the prostate and surrounding areas. From these images, a customized plan for delivering the ultrasound energy is created. The Sonablate software allows the physician to precisely define the treatment zones in order to destroy the entire gland.
Sonablate HIFU is minimally invasive, performed on an outpatient basis and typically lasts 2–4 hours, depending on the size of the prostate. There is no surgery or radiation involved. Patients wear a catheter post-procedure but are able to resume normal activities almost immediately. The Sonablate is the only HIFU device for prostate cancer that does not require an advance surgical procedure (known as a TURP) in order to achieve effective results when treating enlarged prostate glands. Sonablate HIFU can treat large prostates up to 40 grams.
The Sonablate incorporates three-dimensional imaging to provide better visuals of the prostate, especially any irregularities, and allow the physician to create the most effective treatment plan possible. The newest technological enhancement to the Sonablate is tissue change monitoring (TCM) software, which gives real-time feedback to the physician, thus confirming if sufficient energy has been delivered to completely ablate the tissue.
Other cancers
HIFU has been successfully applied in treatment of cancerOncology
Oncology is a branch of medicine that deals with cancer...
to destroy solid tumors of the bone, brain, breast, liver, pancreas, rectum, kidney, testes, prostate. At this stage, cancer treatments are still in the investigatory phases as there is a need to find more about their effectiveness.
HIFU has been found to offer palliative care. CE approval has been given for palliative treatment of bone metastasis. Experimentally, a palliative effect was found in cases of advanced pancreatic cancer.
HIFU may be used to create high temperatures not necessarily to treat the cancer alone, but in conjunction with targeted delivery of cancer drugs. For example, HIFU and other devices may be used to activate temperature-sensitive liposomes, filled with cancer drug "cargo" to release the drug in high concentrations only at the tumor site(s) only where triggered to do so by the hyperthermia device (See Hyperthermia therapy
Hyperthermia therapy
Hyperthermia therapy is a type of medical treatment in which body tissue is exposed to slightly higher temperatures to damage and kill cancer cells or to make cancer cells more sensitive to the effects of radiation and certain anti-cancer drugs...
). This novel approach is resulting in drug concentrations 10 times or more than traditional chemo with a fraction of the side effects since the drug is not released system-wide.
In addition, several thousand patients with different types of tumors have been treated in China with HIFU using ultrasound imaging-guided devices built by several different companies.
Delivering drugs to brain
In current research, HIFU is being used to temporarily open the blood-brain barrierBlood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
, allowing absorption of drugs into the brain. It is most effective when used in combination with a calcium channel blocker
Calcium channel blocker
A calcium channel blocker is a chemical that disrupts the movement of calcium through calcium channels.CCB drugs devised to target neurons are used as antiepileptics. However, the most widespread clinical usage of calcium channel blockers is to decrease blood pressure in patients with...
like verapamil
Verapamil
Verapamil is an L-type calcium channel blocker of the phenylalkylamine class. It has been used in the treatment of hypertension, angina pectoris, cardiac arrhythmia, and most recently, cluster headaches. It is also an effective preventive medication for migraine...
.
Treatment of atrial fibrillation
HIFU has been used to treat the most common heart arrhythmia, atrial fibrillationAtrial fibrillation
Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...
(AF). A minimally invasive catheter based system designed to ablate heart tissue responsible for propagating AF has been approved for use in Europe and is undergoing an FDA approved phase III pivotal efficacy trial in the United States.
History
The first investigations of HIFU for non-invasive ablation were reported by Lynn et al. in the early 1940s. Extensive important early work was performed in the 1950s and 1960s by William Fry and Francis Fry at the University of Illinois and Carl Townsend, Howard White and George Gardner at the Interscience Research Institute of Champaign, Ill., culminating in clinical treatments of neurological disorders. In particular High Intensity ultrasound and ultrasound visualization was accomplished stereotaxically with a Cincinnati precision milling machine to perform accurate ablation of brain tumors. Until recently, clinical trials of HIFU for ablation were few (although significant work in hyperthermia was performed with ultrasonic heating), perhaps due to the complexity of the treatments and the difficulty of targeting the beam noninvasively. With recent advances in medical imaging and ultrasound technology, interest in HIFU ablation of tumors has increased.The first commercial HIFU machine, called the Sonablate 200, was developed by the American company Focus Surgery, Inc. (Milipitas, CA) and launched in Europe in 1994 after receiving CE approval, bringing a first medical validation of the technology for benign prostatic hyperplasia (BPH). Comprehensive studies by practitioners at more than one site using the device demonstrated clinical efficacy for the destruction of prostatic tissue without bloodloss or long term side effects. Later studies on localized prostate cancer by Murat and colleagues at the Edouard Herriot Hospital in Lyon in 2006 showed that after treatment with the Ablatherm (EDAP TMS, Lyon, France), progression-free survival rates are very high for low- and intermediate- risk patients with recurrent prostate cancer (70% and 50% respectively) HIFU treatment of prostate cancer is currently an approved therapy in Europe, Canada, South Korea, Australia, and elsewhere. Clinical trials in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
are expected to begin in 2006. Prostate cancer trials for the new Sonablate 500 are ongoing in the U.S.A. currently.
Magnetic Resonance Guided Focused Ultrasound MRgFUS was first cited in the article "On-line MRI monitored noninvasive ultrasound" by Hynynen K., Damianou C., Darkazanli A., Unger E., Levy M., SchencK J. in Proceedings of the annual international conference of the IEEE engineering in medicine and biology society,October 1992. Cline HE, Schenck JF, Hynynen K, Watkins RD, Souza SP, Jolesz FA Journal of Computer Assisted Tomography [1992, 16(6):956-65] was published nearly the same time. U.S. Patent #5247935. was Filed March 19,1992 The technology was later transferred to InsighTec in Haifa Israel in 1998. The InsighTec ExAblate 2000 was the first MR Guided focused ultrasound system to obtain FDA market approval in the United States.
Haifu Model JC and JC200 by ChongQing Haifu Ltd. are complete ultrasound guided tumor treatment systems, and they were CE approved in 2005 for benign and malignant tumors.
HIFU-2001(By Sumo Corporation Ltd) is an enhanced technology treatment system that does not require anesthesia. Since 2001 it has been used in Asian countries to treat Liver/Pancreas/Bladder/Uterus/Kidney.
Advantages over other techniques
High Intensity Focused Ultrasound is often considered a promising technology within the non-invasive or minimally invasive therapy segments of medical technology. HIFU’s capacity to generate in-depth precise tissue necrosis using an external applicator, with no effect on the surrounding structures, is unique. The history of using therapeutic ultrasound dates back to early in the 20th century. Technology has continually improved and additional clinical applications, both diagnostic and therapeutic, have become an integral part of medicine today.An important difference between HIFU and many other forms of focused energy, such as radiation therapy or radio surgery, is that the passage of ultrasound energy through intervening tissue has no apparent cumulative effect on that tissue.
The absence of cumulative effect of HIFU on the treated tissue means that the treatment can be repeated in case of first HIFU treatment failure or partial treatment of the prostate. As a clean treatment (= non-ionizing) HIFU is also an option to treat prostate cancer recurrence after radiation therapy failure.
Discoveries during use
Currently, the only proven imaging method to accurately quantify the heating produced during HIFU in vivo is Magnetic Resonance Imaging (MRI). MRI also has superior soft tissue contrast and can image in any orientation, making it the state of the art for guiding HIFU treatments. But MRI can't operate in real-time with HIFU, with the current state of the art being one image acquisition approximately every six seconds using a full scan of k-space. Researchers are working to reduce this image acquisition time through some of the speed enhancements common in other areas of MRI, including pulse sequences to scan a reduced k-space, constrained reconstruction, and model-based filtering using data from the bioheat equation.The University of Minnesota produced a dual-mode ultrasound transducer that offers time resolution measured in milliseconds and offers closed-loop, real-time, intensity modulation based on continuous monitoring of tissue response to the HIFU beam. This method offers improved resolution over MRI.
Clinically, MRI-guided HIFU treatments have been tested for uterine fibroids, breast fibroadenomas, breast cancer, bone metastases, and liver tumors. The largest number of patients treated with MRI-guided HIFU have been with uterine fibroids.
USgFUS treatments have been approved with CE for wider range of benign and malignant tumors due to its higher power, precision and realtime monitoring system. The largest number of patients are uterine fibroids.
Ultrasound-guided HIFU treatments have been approved in Europe and Asia. MRI-guided treatments of uterine fibroids have been approved in Europe and Asia, and were granted FDA approval in the US in 2004.
Focal HIFU treatment
With the latest improvements in biopsy techniques enabling to better locate cancer, focal HIFU treatment (i.e. partial HIFU ablation) is now starting to be investigated to further reduce the side effects of cancer treatment.Organizations
The International Society for Therapeutic Ultrasound, founded in 2001, aims to promote clinical, academic and industrial advancement in Therapeutic Ultrasound. Its primary activity is the annual International Symposium on Therapeutic Ultrasound, which has attracted experts in HIFU from throughout the world.The Foundation for Focused Ultrasound Research
Foundation for Focused Ultrasound Research
The Foundation for Focused Ultrasound Research is an American non-profit 501 charity designed to promote both education and research within the area of medical applications of focused ultrasound .- History :...
is an unincorporated association promoting research into medical uses of high intensity focused ultrasound, including HIFU.
The Focused Ultrasound Surgery Foundation
Focused Ultrasound Surgery Foundation
The Focused Ultrasound Surgery Foundation is a 501 non-profit organization based in Charlottesville, Virginia, United States, that promotes the use of magnetic resonance guided focused ultrasound , which uses high intensity focused ultrasound...
(FUSF) is working to shorten the time from technology development to patient treatment, develop new applications and accelerate the worldwide adoption of MR-guided focused ultrasound surgery
See also
- Magnetic resonance imagingMagnetic resonance imagingMagnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
- Medical ultrasonographyMedical ultrasonographyDiagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
- Uterine fibroidsUterine fibroidsA uterine fibroid is a benign tumor that originates from the smooth muscle layer and the accompanying connective tissue of the uterus.Fibroids are the most common benign tumors in...
- Medical deviceMedical deviceA medical device is a product which is used for medical purposes in patients, in diagnosis, therapy or surgery . Whereas medicinal products achieve their principal action by pharmacological, metabolic or immunological means. Medical devices act by other means like physical, mechanical, thermal,...
Further reading
- Magnetic Resonance Guided Focused Ultrasound Surgery, United States Patent #5247935 Harvey Cline, Robert Ettinger, Kenneth Rohling Ronald Watkins, filed March 1992
- H. E. Cline, J. F. Schenck, K. Hynynen, R. D. Watkins, S. P. Souza, and F. A. Jolesz. “MR-guided focused ultrasound surgery,” J Comput Assist Tomogr 16(6), 956-65 (1992).
- Focused US system for MR imaging-guided tumor ablation HE Cline, K Hynynen, RD Watkins, WJ Adams, JF Schenck, RH Ettinger, WR Freund, JP Vetro and FA Jolesz Radiology 1995 194: 731-737Full text
- Nakagawa M.D. PH.D., H, et al., "Initial Experience Using a Forward Directed, High-Intensity Focused Ultrasound Balloon Catheter for Pulmonary Vein Antrum Isolation in Patients with Atrial Fibrillation", J Cardiovasc Electrophysiol", Vol 18, pp. 1–9, February 2007,
- Dubinsky TJ, Cuevas C, Dighe MK, et al. High-Intensity Focused Ultrasound: Current Potential and Oncologic Applications. AJR 2008; 190:191-199
- Haar GT, Coussios C. High Intensity Focused Ultrasound: Past, present, present and future. Int J. Hyperthermia 2007; 23(2):85-87
- Coussios C, Farny CH, Haar GT et al. Role of acoustic cavitation in the delivery and monitoring of cancer treatment by high-intensity focused ultrasound (HIFU). Int. J. Hyperthermia 2007; 23(2):105-120
- Leslie TA, Kennedy JE. High intensity focused ultrasound in the treatment of abdominal and gynaecological disease. Int. J. Hyperthermia 2007; 23(2):173-182
- Wu F, Wang ZB, Chen WZ et al. Extracorporeal focused ultrasound surgery for treatment of human solid carcinomas: Early Chinese clinical experience. Ultrasound Med Biol 2004; 30:245-260
- Haar GT, Coussios C. High Intensity Focused Ultrasound: Physical principles and devices. Int J. Hyperthermia 2007; 23(2):89-104
- Lafon C, Melodelima D, Salomir R, et al. Interstitial devices for minimally invasive thermal ablation by high-intenstiy ultrasound. Int. J. Hyperthermia 2007; 23(2):153-163
- Stewart EA, Rabinovici J, Tempany CM, et al. Clinical outcomes of focused ultrasound surgery for the treatment of uterine fibroids. Fertil Steril 2006; 85:22-29
- Fosse E. Thermal ablation of benign and malignant tumours. Minim Invasive Ther Allied Technol 2006; 15:2-3
- Illing RO, Kennedy JE, Wu F, et al. The safety and feasibility of extracorporeal high.intensity focused ultrasound (HIFU) for the treatment of liver and kidney tumours in a Western population. Br J Canc 2005; 93:890-895
- Wu F, Wang ZB, Chen WZ, et al. Advanced hepatocellular carcinoma: Treatment with high-intensity focused ultrasound ablation combined with transcatheter arterial embolization. Radiology 2005; 235:659-667
- Wu F, Wang ZB Zhu H, et al. Feasibility of US-guided high-intensity focused ultrasound treatment in patients with advanced pancreatic cancer: Initial experience. Radiology 2005; 236:1034–1040
- Kennedy JE. High.intensity focused ultrasound in the treatment of solid tumours. Nature Reviews: Cancer 2005; doi10.1039/nrc1591
- Wu F,Wang ZB, Chen WZ, et al. Extracorporeal high intensity focused ultrasound ablation in the treatment of 1038 patients with solid carcinomas in China: an overview. Ultrasound Sonochemistry 11 2004; 149-154
- Kohrmann KU, Michel MS, Gaa J, et al. High intensity focused ultrasound as noinvasive therapy for multilocal renal cell carcinoma: Case study and review of the literature. J Urol 2002; 167:2397–2403
- Kennedy JE, Wu F, Haar TG, et al. High-intensity focused ultrasound for the treatment of liver tumors. Ultrasonics 2004; 42:931-935
- Wu F, Wang Z, Chen W, et al. Extracorporeal High-Intensity Focused Ultrasound for treatment of solid carcinomas: Four-year Chinese clinical experience. In: Andrew M, Crum L, Vaezy S, editors. Proceedings of the 2nd International Symposium on Therapeutic Ultrasound. Seattle: University of Washington; 2003; 34-43
- Wu F, Wang ZB, Chen WZ, et al. Preliminary experience using high intensity focused ultrasound for the treatment of patients with advanced stage renal malignancy. J Urol 2003; 170(6 Pt 1): 2237–2240
- Stewart EA, Gedroyc WM, Tempany CM, et al. Focused ultrasound treatment of uterine fibroid tumors: Safety and feasibility of a noninvasive thermoablative technique. Am J obstet Gynecol 2003; 189:48-54
- Wu F, Chen WZ, Bai J, et al. Tumor vessel destruction resulting from high intensity focused ultrasound in patients with solid malignancies. Ultrasound Med Biol 2002; 28:535-542
- Chen WS. Investigations on the destruction of ultrasound contrast agents: fragmentation thresholds, inertial cavitation and bioeffects [dissertation]. Seattle, WA:University of Washington 2002
- Wu F, Chen WZ, Bai J, et al. Pathological changes in human malignant carcinoma treated with high-intensity focused ultrasound. Ultrasound Med Biol 2001; 27:1099–1106
- Sibille A, Prat F, Chapelon JY, et al. Extracorporeal ablation of liver tissue by high intensity focused ultrasound. Oncology 1993: 50:375-379
- Haar TG, Kennedy JE, Wu F. Physical characterization of extra corporeal high intensity focused ultrasound (HIFU) treatments of cancer. Ultrasound Med Biol (in press)
- Chen J, Zhou D, Liu Y, Peng J, Li C, Chen W, Wang Z. A Comparison Between Ultrasound Therapy and Laser Therapy for Symptomatic Cervical Ectopy. Ultrasound Med Biol 2008 May 8.
- Li YY, Sha WH, Zhou YJ, Nie YQ. Short and long term efficacy of high intensity focused ultrasound therapy for advanced hepatocellular carcinoma. J Gastroenterol Hepatol. 2007 Dec;22(12):2148–2154
- Pan JY, Liu YH, Yang QH, Jia L, Ma J. Toxicity attenuation and efficacy potentiation effects of FU Zheng Yang Yin Decoction with HIFU on the experimental model of VX2 cancer in rabbits' liver. Zhong Yao Cai. 2007 Nov;30(11):1425–1429. [Article in Chinese]
- Yu T, Xu C. Hyperecho as the Indicator of Tissue Necrosis During Microbubble-Assisted High Intensity Focused Ultrasound: Sensitivity, Specificity and Predictive Value. Ultrasound Med Biol. 2008 Mar; 29.
- Qiao L, Song WQ. Research on data management of medical equipments in HIFU. Zhongguo Yi Liao Qi Xie Za Zhi. 2007 Sep;31(5):333-337.
- Yang Z, Cao YD, Hu LN, Wang ZB. Feasibility of laparoscopic high-intensity focused ultrasound treatment for patients with uterine localized adenomyosis. Fertil Steril. 2008 Apr 26.
- Loulou T, Scott E. Thermal Dose Optimization in Hyperthermia Treatments by Using The Conjugate Gradient Method. Numerical Heat Transfer, Part A. 42; 661-683, 2002.
- Tempany CMC, Stewart EA, McDannold N, Quade B, Jolesz F, Hynynen K. MRI guided focused ultrasound surgery (FUS) of uterine leiomyomas: A Feasibility study. Radiology 2003; 226:897-905.
External links
- FOCUS - Ultrasound simulations using MATLAB
- Pine Street Foundation Review Article (Winter 2006)
- UROTODAY Hifu Resource center
- Despite Doubts, Cancer Therapy Draws Patients from The New York Times on 18 January 2008