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Magnetic Stereotaxis System (MSS)...

Better Way Found to Get Inside Your Head

American neurosurgeons develop flexible catheter system

By Robert Preidt
HealthScout Reporter

SATURDAY, Nov. 4 (HealthScout) -- A new system that uses magnets and advanced computer imaging allows surgeons to precisely direct a flexible catheter along a curved path within the brain or other parts of the body.

The Magnetic Stereotaxis System (MSS), developed by a team of American neurosurgeons, is touted as a safer, less invasive and more effective way to biopsy brain tumors. Other applications may include diagnosing and treating cardiovascular conditions, such as coronary artery disease, cardiac arrhythmia and aneurysms.

Currently surgeons pinpoint the location of a brain tumor through magnetic resonance imaging (MRI) technology, but doctors must manually guide surgical instruments on a straight-line path to the target location, possibly passing through and damaging vital brain tissue.

The safety and performance of the MSS was first tested by directing catheters along a curving path to obtain biopsy specimens in pig brains, according to a study published in the August 2000 Journal of Neurosurgery.

"Whether it's used in the brain or other parts of the body, we're now able to accurately control the tip of a catheter through a direct magnetic interaction," says the neurosurgeon team's leader, Dr. M. Sean Grady, professor and chairman of neurosurgery at the University of Pennsylvania, Philadelphia.

The MSS system uses a small magnet, slightly larger than a grain of rice, at the tip of the catheter which can be guided by powerful external magnets around the head or any other area of the patient's body being probed.

The target and path are first defined using MRI. Fluoroscopic imaging is combined with the MRI to advance the flexible catheter.

As the catheter moves, the MSS system plots the actual path, comparing it to the designated path, and adjusts the magnetic guidance accordingly. The surgeon gets immediate feedback about the catheter's path and can make necessary corrections.

The navigation process takes only a few minutes. Once the catheter reaches the tumor, the guide wire is withdrawn, leaving the catheter in place. A highly flexible biopsy tool is inserted, the biopsy is taken, and the catheter is removed.

The MSS systems is ideal for performing minimally invasive surgical procedures, not just in the brain but other parts of the body, Grady says.

"When you use it in other applications, such as blood vessels, you know where the branch point is, and you can get the catheter tip right up to the branch point and make it turn into the branch," he says.

The system took 15 years to develop and only became possible with advances in computers, software, imaging and magnets.

"I think it has a lot of promise," says Dr. Ralph G. Dacey Jr., professor and chairman of the department of neurosurgery at Washington University in St. Louis, Mo.

Dacey helped develop the MSS and conducted initial clinical trials on three patients with intracranial tumors who required biopsies.

"The idea of this part of the trial was to demonstrate its feasibility and safety, and it did work efficiently. It was safe," Dacey says.

The ability to navigate the MSS along curved paths isn't its only major advantage over existing methods. The new system can reduce the number of procedures endured by a patient.

"We can get a catheter where it needs to go and then manipulate the catheter to a subsequent place later without doing another operation," Dacey says.

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