A team of researchers at MR-Center of the University Children's Hospital (Zurich, Switzerland) are one step closer to providing noninvasive procedures in nearly every part of the body using MRI guided ultrasound.

They recently completed a pilot study using transcranial MR-guided high intensity focused ultrasound (HIFU) to treat 10 patients with neuropathic pain (Medical Device Daily, July 15, 2009).

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 researchers implemented and optimized a prototype system for transcranial magnetic resonance-guided high-intensity focused ultrasound (HIFU) for neurosurgical interventions. The HIFU system ExAblate 4000, developed by InSightec (Dallas), has been combined with a 3 Tesla high field GE MR-scanner. The two systems together provide a platform for image-guided, non-invasive interventions.

These findings are set to be published in a forthcoming issue of Annals of Neurology and have the potential to turn the way the medical community thinks about HIFU on its ear, say researchers of the study.

Neal Kassell, MD, a neurosurgeon at the University of Virginia (Charlottesville), and chairman of the Focused Ultrasound Surgery Foundation, which helped fund the study, said that the benefits of this procedure were numerous.

"First of all it's totally non invasive and you're able to treat the patient in real time. Plus the effect of the procedure is known immediately," Kassell told Medical Device Daily.

"It's proof that through the intact skin and skull you can make lesions in an awake person's brain," he said. "These results are huge milestone in the field of focused ultrasound. The fact that you can treat the brain with this procedure means you can treat other things. I think in the next few years we'll see the liver, pancreas and prostate treated this way."

The study was partially funded by the Focused Ultrasound Surgery Foundation. The Foundation funds translational and clinical research into new therapeutic applications of MR-guided focused ultrasound (MRgFUS).

The preliminary results in these patients are consistent with conventional therapy — radio frequency ablation — which is an invasive procedure and 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 radio frequency to create the lesion.

Researchers say the procedure is painless and quick.

Instead of going in for surgery, the patient is basically going in for an MRI. The patient is sent through an MRI scanner similar to a regular diagnostic MRI scanner only this scanner has a special ultrasound system integrated into it which can non-invasively ablate tissue inside the brain. It essentially is an outpatient procedure and no anesthesia is used at all.

"This research demonstrates that transcranial MR-guided focused ultrasound can be used non-invasively to produce small thermal ablations with extreme precision and accuracy deep in the brain," he said.

The study proved that researchers can perform successful operations without opening the cranium or physically penetrating the brain with medical tools, something that appeared to be unimaginable only a few years ago.

According to Kassell, the key advantage of focused it safer than conventional surgery because it avoids the associated risks of complications such as infection, hemorrhage, and collateral damage to normal brain structures.

For years, HIFU has been used for the treatment of uterine fibroids and tumors of the prostate gland. However, its application to the brain through the intact skull for non-invasive neurosurgery was not possible until recently, because of complications.

The plan now is for other research sites are now expected to initiate clinical studies using Transcranial MR-guided focused ultrasound for brain disorders within the next year, including studies for Parkinson's disease, essential tremor, and brain tumors.

"I posit that in 10 years from now that people will either be treated by this procedure or they'll know someone who has been treated by this procedure," Kassell said. "But for now we're very very, very much on the ground floor."

Omar Ford, 404-262-5546; omar.ford@ahcmedia.com