Assessing Blood Flow

Fran Oldford, RN, Supervisor of the Non-Invasive Vascular Lab at NYUMC, explains: "The carotid duplex scan, our standard approach in studying blood flow to the brain, consists of two techniques. Ultrasound allows us to visualize the internal anatomy of the carotid artery. Doppler analysis measures the velocity of blood flow through the artery, which is an indication of the degree of narrowing."

"It’s important to measure this with great precision," says neurologist Keith Siller, MD, "because total closure would generally rule out the most effective therapy for this condition, which is carotid surgery. Patients often come to us, having been told their carotid was closed, but our doppler lab finds a tiny opening.

While blockages of the carotid artery in the neck are probably the most common cause of stroke, it is also important to understand disease beyond this point within the brain itself. This is where transcranial doppler (TCD) is invaluable. It allows us to measure blood flow in the major branches of the carotid arteries by way of a small ultrasound probe placed against the skull, eyes, and back of the head. When combined with other non-invasive tests, it helps provide a more complete picture of the blood flow dynamics in the brain and helps us understand how blockages in the carotid arteries are compensated for by other vessels in both sides of the brain. arteries and heart. NYUMC cardiologists Itzhak Kronzon, MD, and Paul Tunick, MD, using a new application.

New View of the Aorta: ‘Falling Rock Zone’

Approximately 60-70% of strokes are caused by clots, originally thought to be formed in the carotid for the technique known as transesophageal echocardiography (TEE), discovered that the aorta was involved as well.

TEE had been developed as a method to visualize the heart from the esophagus. Drs. Tunick and Kronzon found that by rotating the device, "we could see the aorta from a new vantage point. We saw protruding plaques, often with large, loosely attached clots, which could become dislodged and travel to other sites, including the brain. Increasingly, neurologists now view TEE of the aorta as an important part of a complete stroke workup."

Pictures of the Brain in Action

Brain imaging is becoming more accurate and clinically useful than ever," according to neuroradiologist Edmond Knopp, MD. "Rapid magnetic resonance imaging (MRI) techniques provide sequences of scans spaced so closely in time that we can observe the brain function, in addition to anatomy."

"For example, perfusion imaging measures cerebral blood volume at the capillary level. It shows an infarct as a ‘cold spot’ because of the lack of blood. It helps us pinpoint tissue surrounding the infarct that is at risk and that might be saved with aggressive therapy."

"Magnetic resonance imaging (MRI) techniques provide sequences of scans spaced so closely in time that we can observe the brain function"

Another advanced MRI technique, diffusion imaging, registers motion of water between the cells of the brain. Cells deprived of blood become swollen, restricting the water’s ability to move. This process occurs within minutes, enabling the clinician to distinguish a new infarct from an old one"something a standard MRI can’t do.