(Canadian Press) -- New research will help doctors identify stroke patients who are the best candidates to have brain-damaging blood clots sucked out by a vacuum cleaner device.

Dr. Mayank Goyal, director of the Seaman MR Research Centre at the University of Calgary, presented his work at the Canadian Stroke Congress in Quebec City on Tuesday.

Outcomes are best when the proper patients are selected for the procedure through correct interpretation of brain scans soon after arrival at the hospital, he indicated.

Only really large strokes are suitable for the technique, which uses a tool called the Penumbra System to break down and suck out the clot. If used within a few hours of an ischemic stroke, it can reverse the effects of stroke by restoring blood flow to affected areas of the brain, he said.

Dr. Antoine Hakim, CEO of the Canadian Stroke Network, said a CT scan will tell a doctor whether a patient is a candidate.

"The Penumbra system is a system that allows the introduction of a catheter under neuro-radiology control all the way up to the clot. The vacuum pump is turned on and the clot is sucked out," explained Hakim, a neurologist who was not involved in the research.

"The issues have been that for reasons that we couldn't understand until Dr. Goyal put his expertise to work on this, it didn't seem to work all the time and there were all kinds of complications with it. ... And so what he did was he studied and is reporting on the imaging criteria."

In reading the brain scans, Goyal said doctors need to apply ASPECTS, the Alberta Stroke Program Early CT Score. The scans allow doctors to rule out a brain hemorrhage and to evaluate the amount of brain tissue already affected, he said.

When looking at the use of the Penumbra system in an international study, the researchers saw that only 25 per cent had good outcomes, Goyal said in an interview.

But when the data were looked at again using the scoring system, 62 per cent of those with good ASPECTS had a good outcome when the Penumbra system was used, he said.

Hakim said the other important factor in the success of the Penumbra system is the time from onset of the stroke to when the catheter is inserted and the suction is turned on.

"The longer the period is, the less likely the outcome is to be good."

Patients with good ASPECTS and a period of time equal to or less than 360 minutes (six hours) had better clinical outcomes compared to those who had to wait longer.

The main treatment for ischemic stroke is the clot-busting drug tPA, but it must be administered within three hours of stroke to work. The Penumbra system may successfully salvage brain cells for more than just the first three hours, the researchers said.

Goyal said only 30 to 40 doctors across Canada have the expertise to use the Penumbra system, which involves threading a catheter through the groin to the neck in a blood vessel.

It's key that someone having a stroke gets to the hospital quickly, and that hospitals are set up to do quick imaging and evaluation, he said.

Goyal said his next step is to set up a website so that doctors around the world can learn about ASPECTS and how to evaluate good candidates for the suction procedure.

Copyright 2010, The Canadian Press