While Zurich trials have proven that MR-guided ultrasound is an alternative to invasive surgical procedures for neuropathic pain, the procedure is approved in the U.S. for uterine fibroids. Meanwhile, clinical trials are being conducted for brain disorders, breast tumors and pain from bone metastasis. Trials in the U.S. and abroad for Parkinson's Disease, brain tumors and prostate cancer are expected to start this year.

A team of researchers at the MR-Center at the University Children's Hospital in Zurich recently completed a pilot study using MR-guided focused ultrasound, treating 10 patients with neuropathic pain.

The origin of chronic pain in these patients included post amputation phantom limb syndrome, nerve injury, stroke, trigeminal neuralgia and post herpetic neuralgia from shingles.

The study was partially funded by the Focused Ultrasound Surgery Foundation, which funds research for clinical trials attempting new therapeutic applications for MR-guided focused ultrasound (MRgFUS), a procedure that is still in its infancy but is expected to be the wave of the future, since it is non-invasive and reduces or eliminates the need for surgery, along with its many complications.

The preliminary results in the patients with neuropathic pain are consistent with conventional therapy--radiofrequency ablation--an invasive procedure that involves making an incision in the scalp, drilling a hole in the skull, inserting an electrode through normal brain tissue into the thalamus, and using radiofrequency to create the lesion.

"The great leap forward is integrating MR with focused ultrasound," Rolf Taylor, director of communications for the Focused Ultrasound Surgery Foundation, tells DOTmed News. "Focused Ultrasound is non-invasive. The source of focused ultrasound energy for this type of brain treatment is outside of the body, yet it creates a focal point of energy deep in the brain," Taylor says. "The procedure heats the target tissue at the focal point in a very controllable way, all the time monitored using intraoperative MR imaging and MR thermometry."

Taylor says MR technology has led to what he calls "the most advanced thermometer in the world." MRI thermometry provides a detailed thermal map in real time," he says. "Because focused ultrasound creates heat, the medical team can see exactly what is happening in real time without doing invasive surgery."

So by combining the traditional MRI view to locate the target site for ablation, and MR thermometry, it is possible to precisely ablate the target tissue non-invasively using focused ultrasound while monitoring the procedure, Taylor says.

Millimeter Precision and Accuracy

Neal Kassell, M.D., a neurosurgeon at the University of Virginia, and chairman and founder of the Focused Ultrasound Surgery Foundation, tells DOTmed that MR guided focused ultrasound is a way of treating diseases with "millimeter accuracy and precision."

He says that choosing the target area for surgery is done with an MR scan. While treatment is occurring, surgeons do a scan every one or two seconds, so they can see in real time precisely where to operate.

Avoids Ionizing Radiation

There are some similarities to radiosurgery--both procedures focus energy from a source outside the head onto a specific target site within the brain. However, focused ultrasound avoids some of the complications associated with ionizing radiation and in theory there are no exposure limitations. In addition, the medical team can see the results of the intervention immediately. Radiation effects are not visible during the procedure, and so cannot achieve the precision and accuracy which is possible with focused ultrasound, Taylor explains.

Clinical Trials En Mass

While MR-guided ultrasound is approved in the U.S. for uterine fibroids, clinical trials are currently underway for brain disorders, breast tumors and pain from bone metastasis, Dr. Kassell says.

He says he also expects to see clinical trials in the U.S. and abroad conducted for Parkinson's Disease, brain tumors and prostate cancer this year.

Dr. Kassell concludes that the focused ultrasound procedure, which does not require general anesthesia, may replace other forms of minimally invasive surgery and most radiation therapy because it has a lower complication rate than surgery and does not use ionizing radiation.

For instance, he says some prostate cancer patients who have surgery suffer from erectile dysfunction and incontinence. Focused ultrasound may reduce or possibly eliminate these complications.

Source: Focused Ultrasound Surgery Foundation.