Never before have physicians had access to such a powerful and precise means of treating disease that is also noninvasive, nontoxic, and so widely applicable. As it gains in acceptance, it should eliminate the need for many invasive procedures and most radiation treatments, open the way to entirely new approaches for treating disease, and transform the process of drug delivery. It is based on two groundbreaking core technologies - magnetic resonance imaging and focused ultrasound. Top

The human body is primarily made up of water molecules, each of which has two hydrogen atoms. Apply a big enough magnetic field to those hydrogen atoms, and they line up like iron filings. Direct a radio wave at them at just the right frequency, and they wobble on their axis briefly before snapping back into place. MRIs induce this alignment, makes them resonate, and measures the characteristic energy they give off, which differs from tissue to tissue.

The result: uncommonly detailed, real-time images of normal and abnormal anatomical tissues that can be visually sliced in any direction and that can be generated over an extended period of time without any danger to the patient. In addition, MRIs can also be used to measure tissue temperature as well as structure. Together, these characteristics make MRI the ideal technology to guide focused ultrasound. Top

Ultrasound works like sonar. High-frequency sound waves can penetrate human tissue, but when they hit the boundary between different kinds of tissue, some bounce back. The ultrasound machine translates these echoes into images.

Ultrasound is a diagnostic tool. Because it is harmless, it is commonly used during pregnancy to monitor the health of the fetus. It is also used to diagnose prostate disorders, evaluate blood vessel narrowing, and assess heart function. Top

Turn the sound up on your stereo, and objects start vibrating. If an object can't vibrate freely, it transforms the sound wave energy into heat. That is the basic principle behind focused ultrasound.

Normally the amount of heat produced by ultrasound is both insignificant and imperceptible, but when you take an series of narrow ultrasound beams, arrange them in an array, and focus them on a single point within the body, that spot will heat up, just as if you were using a magnifying glass to focus the sun's rays to burn a hole in a piece of paper.

Focused ultrasound gives physicians the ability to produce precise amounts of heat and vibration at a minute spot within the body with pinpoint accuracy. The heat and vibration can be used to destroy or break up tissue or to release a drug at a specific location without affecting adjacent tissues. Destroyed tissue is absorbed by the body. Like MRI, focused ultrasound is not invasive nor does it use radiation. Top

Currently, ultrasound images are being used to guide focused ultrasound surgery. Although these images are adequate for treating uterine fibroids and prostate cancer, their resolution is not sufficient for interventions that require a high degree of precision. In addition, ultrasound images do not provide any indication of tissue temperature. Top

Magnetic resonance gives physicians access to real-time, high-resolution images that can be used to monitor anatomy and temperature at virtually any point in the body. The quality of these images is much higher than ultrasound images. This information gives them the ability to tap the powers of focused ultrasound with unprecedented precision.

The process used to perform MR-guided focused ultrasound surgery highlights the advantages of using magnetic resonance to guide focused ultrasound surgery:

• Using MRI, the surgical team can create a detailed image of the targeted area.
• With this image, they can plan the procedure in great detail, precisely identifying tissues to be treated and structures to be avoided.
• During the operation itself, the MRI can provide real-time guidance, allowing the team to monitor tissue temperature and adjust treatment as necessary.
• Once the procedure is over, the MRI can be used to confirm the effectiveness of the treatment and to help determine if retreatment is necessary.

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Because it is noninvasive, MR-guided focused ultrasound surgery can be performed on an outpatient basis. The patient requires only minimal sedation, experiences only slight discomfort, recovers much more quickly, and runs a much lower risk of complications and infection. Elderly or seriously ill patients who would not be able to withstand the rigors of invasive surgery should more easily tolerate MR-guided focused ultrasound procedures. Top

MR-guided focused ultrasound uses heat to destroy tissue, rather than radiation. Unlike radiation therapy, there is no maximum cumulative dose - focused ultrasound can be repeated over and over again, for instance, until a tumor is destroyed - and the effects on tissue are immediate. Top

MR-guided focused ultrasound can be focused on a spot 1 mm in diameter virtually anywhere in the body. The heat and vibration applied at that spot can be controlled with a high degree of accuracy and the area affected can be sharply delineated to protect healthy tissue. The physician can target and plan the procedure in great detail, monitor the progress of the procedure in real-time, and confirm its effectiveness. Top

Vibrations produced at lower energy levels by MR-guided focused ultrasound potentially could be used to dissolve blood clots in the case of an ischemic stroke or heart attack, restoring blood flow and minimizing or even eliminating the destruction of healthy tissue. This technology may potentially be used to treat cardiac arrhythmias such as atrial fibrillation by destroying the tissue that is sending out abnormal electrical impulses. This tissue is currently destroyed using radio frequency technology. Top

MR-guided ultrasound advances the treatment of cancer in three ways. First, it can be used to eliminate benign tumor tissue with absolute precision, leaving the normal surrounding tissues and organs unaltered. Second, it provides a dramatic advance over radiation therapy. There is no cumulative dose effect, no limitation in lesion size, no limitation on the number of treatments, and no secondary tumors caused by the radiation itself. Finally, for malignant tumors, it has the potential to greatly increase the effectiveness of chemotherapy, though systems that allow high-dosages of chemotherapy to be released only at the target site. In essence, MR-guided focused ultrasound has the potential to convert metastatic cancer from a lethal to a chronic, treatable disease. Top

The current methods of delivering drugs are not selective. As a result, the potency of the drug has to be reduced to minimize its systemic impact on surrounding tissue as it circulates toward its target.

MR-guided focused ultrasound could potentially be used to release drugs at their target. Drugs would be encapsulated in fat molecules, enclosed in tiny bubbles, or bound to nanoparticles and injected into the body. These delivery vehicles would be stable at normal body temperatures, releasing their payload only when subject to the heat or vibration of focused ultrasound.

Using MR-guided focus ultrasound, physicians could deliver therapies - including antibiotics, chemotherapy agents, genes, or growth factors - in much higher concentrations at the exact tissue site where they are needed, without the systemic toxicity associated with current methods. Top

The ability of MR-guided focused ultrasound to release drugs or genes at targeted locations is particularly promising for neurological diseases. Early experiments have shown that focused ultrasound has been found effective in opening the blood brain barrier temporarily, allowing delivery vehicles containing drugs and genes to reach specific regions of the brain. Using algorithms developed to allow focused ultrasound energy to penetrate through the skull, MR-guided focused ultrasound could be used to trigger their release with precision.

This development holds significant promise for treating movement disorders like Parkinson's disease, psychiatric diseases like depression and obsessive-compulsive disorder, and pain disorders that don't otherwise respond to treatment. In addition it may enable the use of gene therapy for stroke and spinal cord injury. Top

MR-guided focused ultrasound technology has just begun to have an impact. Currently, MR-guided focused ultrasound surgery has been approved by the U.S. Food and Drug Administration (FDA) for treatment of uterine fibroids and has obtained CE-mark approval in Europe for uterine fibroids and pain from bone metastases.

There are ongoing clinical trials in the United States for bone metastases, uterine fibroids, breast tumors, and brain tumors. In the near future, clinical trials will begin for prostate and liver tumors, while studies for stroke, epilepsy, movement disorders, pancreatic, and kidney disorders are in the planning stage. Top

Within ten years, further improvements in magnetic resonance will allow the noninvasive visualization of small clusters of abnormal cells. When these imaging advances are coupled with projected technological improvements in both focused ultrasound and in drug delivery vehicles, an even wider spectrum of new medical applications can be imagined. Top

MR-guided focused ultrasound is at an early stage in its development, and its safety and efficacy to address specific diseases must be demonstrated through rigorous clinical trials that are scrutinized by the regulatory agencies like the FDA. Insurance companies must accept MR-guided focused ultrasound as standard treatment and physicians be made more aware of its superiority to conventional treatments. Top

The Focused Ultrasound Surgery Foundation was founded in 2006 to foster the rapid development of new applications and to radically shorten the worldwide adoption of this breakthrough technology. Our goal is to serve as a focal point for a collaborative community for advancing MR-guided focused ultrasound technology, one that that spans medical specialties and that brings together universities and government funding agencies with pharmaceutical and medical device companies, private foundations, and venture capital.

As part of this effort, we have funded a number of research projects relating to various applications of MR-guided focused ultrasound, provided fellowship funding to train physicians in the use of this revolutionary technology, and  hosted our first International MRgFUS Symposium in October 2008, as well as a two-day workshop on MRgFUS and the brain in March 2009. Top