The MRgFUS Technology

Sonication

In MR-guided focused ultrasound (MRgFUS), MR images of the target tissue are first obtained and then reviewed by the physician. This allows the physician to identify the volume of the fibroid to be treated, mark the shape of the treatment site on the images and then review the treatment plan. Once treatment begins, an ultrasound transducer generates a point of focused energy called a sonication. The sonication raises the temperature of the targeted area within the fibroid tissue, which causes cells in the fibroid to die. During sonication, the process is carefully monitored through real-time MR images. The process of sonication is repeated at multiple adjacent sites until the entire fibroid has been treated.

Sonication uses tightly focused high-energy ultrasound waves to kill tissue. Sound waves passing through tissue are partially absorbed and converted to heat. With proper focusing and sustained energy input, a small and targeted focus of heating (temperatures of 65-850C/149-1850F are produced in the focal zone) can be achieved at varying depth within tissues and adjusted to kill a small (size of a grain of rice) piece of a fibroid. Larger volumes of a fibroid can be treated piece by piece. The use of focused ultrasound waves to heat and destroy a piece of fibroid is like using a magnifying glass to focus the sun’s energy on a single spot and heat it.

Sonication

The principle of using high-energy ultrasound beams for disease treatment dates to 1954, but early efforts were limited by lack of image guidance and lack of accurate monitoring of treatment effects. In 1984, extracorporeal shockwave lithotripsy (fragmentation of urinary stones by targeted high energy ultrasound) became the first clinical application of high-energy ultrasound for disease treatment to be approved by the FDA. Interest in focused ultrasound for tumor ablation re-emerged in the 1990s due to the convergence of advances in medical imaging, ultrasound technology, and focal therapy.

The FDA approved MRgFUS for the treatment of fibroids in 2004.  In July 2010, UCSF became the first site in the country to be awarded a high-end instrumentation grant from the National Institute of Health for purchase of an MRgFUS system for focussed ultrasound and treatment of uterine fibroids.

Focused ultrasound was named by TIME Magazine as one of the 50 most inspired ideas, innovations and revolutions of 2011.