
DOPPLER PREDICTS STROKE
Meteorologists use it to track storms. Now doctors are using a similar version of doppler radar to look at blood flow in the brain and help prevent stroke.
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Airplanes are his hobby. But Wade Hilmo's been grounded from flying real ones since January.
Wade Hilmo
Aneurysm Patient
"I could feel kind of a tingling start at the back of my neck, and it came forward over the top of my head and then as soon as it came over the top of my head I got really dizzy."
A ruptured aneurysm was bleeding in Wade's brain.
Wade Hilmo
"One of the things that strikes me is if I had been living 50 years ago, or 100 years ago, this probably would have been fatal."
But today's technology may have saved his life. After surgery, doctors used transcranial doppler to see if Wade was at risk of having a stroke -- a common result of a ruptured aneurysm.
David Newell, MD
Neurosurgeon
Swedish Medical Center
Seattle, WA
"Every day or twice a day we can go in and check the vessels with the ultrasound to see if they were going into spasm, which is the prelude to a possible stroke in these patients."
It's a slight variation of the same doppler technology meteorologists use to watch a storm develop as it happens.
It uses ultrasound to measure blood flow in the brain in real time. The technology can also be used to help treat migraines, and unlike other methods, it's non-invasive.
David Newell, MD
"It's based on the same Doppler principal where sound waves are sent toward an object and then received waves that are reflected off that object are received by the equipment."
For Wade, it meant peace of mind during a scary time.
Wade Hilmo
"I knew that it was a very serious thing."
He's back on his feet now -- fully recovered -- and hopes to soon be back in the air.
Transcranial doppler can be used on anyone at risk for stroke or migraine. Researchers are also studying the technology to help dissolve blood clots in the brain. Another goal -- to develop a transcranial doppler the size of a PDA that patients can wear 24 hours a day to detect warning signs of a stroke.
WHAT IS IT? Transcranial Doppler (TCD) is a test that measures the velocity of blood flow through the brain's blood vessels. It is used to help diagnose possible illnesses.
PURPOSE: The blood that flows through the brain distributes nutrients to the brain and removes wastes. This flow maintains the high rate of metabolism necessary for the brain to function. Restrictions in blood flow may occur from vessel narrowing (stenosis), clot formation (thrombosis), blockage (embolism), or blood vessel rupture (hemorrhage). Lack of sufficient blood flow threatens brain tissue and may cause a subarachnoid hemorrhage (bleeding from a ruptured aneurysm) and may cause a stroke.
HOW IT WORKS: Pulses of ultrasound, at frequencies of around 2 MHz, are directed using a handheld transducer towards the base of the skull. The frequency shift, called the "doppler effect," in the reflected sound indicates the characteristics of the brain. Images can also be reconstructed, like the sonography, which is used when mothers get scanned during pregnancy. Different sections of the brain can be seen by altering the location, angle and depth setting of the transducer. The most common places to view in the brain are located in the orbit (of the eye) and in the temporal regions.
ADVANTAGES: David Newell, M.D., says, until TCD there was no good non-invasive way to measure blood vessels. He cites this as a problem. "When there is bleeding around the blood vessels in the brain, it can cause them to go in to spasms, that can cause a stroke," says Dr. Newell. He says TCD is reliable and can warn doctors about strokes. "It's extremely accurate," he says.
TCD is a relatively quick and inexpensive test and is growing in popularity. The equipment used for these tests is becoming increasingly portable, making it possible for a clinician to travel to a hospital, doctor's office, or nursing home for both inpatient and outpatient studies. Dr. Newell says TCDs are being made as small as PDA's (palm pilots). "The goal is a portable device for patients to wear 24 hours, to detect warning signs for strokes," he says. The test is easily repeated and doesn't use contrast agents, which decreases the risk of allergic reactions and other risks to the patient.
PREPARATION: TCD is non-invasive and has little or no risk. Experts recommend patients remove contact lenses and avoid the use of eye makeup, since the gel used to help make the movement of the transducer easier is likely to smear it.
Colleen Douville
Seattle Neuroscience Institute
James Tower 550 17th Ave, Ste 500
Seattle, WA 98122
Colleen.douville@swedish.org
www.swedish.org
Copyright © 2006 Ivanhoe Broadcast News, Inc.
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