Stroke Awareness

In the United States, the median time to treatment is 4.5 hours, every hour is 11 months of healthy life lost⁴. Raising awareness is one step in the larger effort to eradicate neurological illnesses, diseases, and ailments.
Data statistics regarding stroke overlaid on a map of US.

Know the Signs
F. A. S. T

Face Drooping

Ask the person to smile. Does one side droop?

Arm Weakness

Ask the person to raise both arms. Does one arm drift down?

Speech Difficulty

Ask the person to repeat a simple sentence. Do they slur?

Time to Call 911

Time is brain. Call 911 right away.

Transcranial Doppler Ultrasound (TCD) is Required to Become a Certified Comprehensive Stroke Center

What is TCD?

TCD is a noninvasive and painless ultrasound method that uses sound waves to evaluate blood flow in and around the brain. There is no special contrast or radiation involved in the test.

During the TCD exam, high frequency sound waves are transmitted through the tissues of the skull. These sound waves reflect off blood cells moving within the blood vessels, allowing the TCD system to measure the rate and direction of blood flow in the main cerebral arteries known as the Circle of Willis.

While most forms of ultrasonography deliver images of the tissue studied, TCD delivers audible sounds that can be heard, recorded, and examined.

A diagram of the circle of willis

Why is TCD Used?

Physicians recommend this highly accurate and sensitive test for patients with stroke or stroke-like symptoms. It is used to assist in the diagnosis of a wide range of conditions affecting blood flow to, and within, the brain.

Vasospasm Detection

For assessment of cerebral vasospasm after spontaneous or traumatic subarachnoid hemorrhage (SAH)

90% sensitive
in detecting vasospasm after SAH⁵
Hemodynamic Monitoring

Delivers continuous real-time data on embolic activity and blood flow to enable immediate treatment decisions

Right-to-Left Shunt (RLS) Detection

Assessment of vascular shunting to provide insight into the underlying cause of a stroke

96% sensitive
in detecting a RLS⁷
Perioperative Monitoring

Provides critical insight into hemodynamic patterns during high-risk cardiovascular procedures.

Emboli Detection

Provides real-time detection, localization, and quantification of emboli, which are a significant source of stroke risk.

A person with their transtemporal window highlighted

The transtemporal window is a thin spot in the skull that allows ultrasound waves to pass through the bone

Why Isn’t TCD More Broadly Used?

Similar to other ultrasound-based tests, TCD uses sound waves to evaluate structures inside the body, in this case the blood flow in the brain.

However, the brain is protected by the skull and ultrasound waves cannot easily pass-through bone. TCD testing requires the operator to be able to find the transtemporal window (thin part of the bone in the skull) that will allow the ultrasound waves to penetrate the skull and find the blood vessels that need to be evaluated.

Finding this window is one of the most difficult parts of the exam. It is unique to this form of ultrasound, resulting in a high learning curve compared to other ultrasound tests.

<5% of U.S. ultrasound personnel are trained to do TCD exams

Because of the lack of TCD-trained clinicians, many hospitals are not able to provide TCD testing for their patients

Picture of the NovaSignal Platform


1. Tsao CW, Aday AW, Almarzooq ZI, Alonso A, Beaton AZ, Bittencourt MS, et al.; on behalf of the American Heart Association Council on Epidemiology and Prevention Statistics Committee and Stroke Statistics Subcommittee. Heart Disease and Stroke Statistics—2022 Update: A Report from the American Heart Association. Circulation. 2022; 145:e00–e00. doi: 10.1161/CIR.0000000000001052.

2. Proposed Standardized Neurological Endpoints for Cardiovascular Clinical Trials. Alexandra J. Lansky, MD. Eur Heart J. 2018 May 14; 39(19): 1687–1697.

3. Swerdel JN, Rhoads GG, Cheng JQ, Cosgrove NM, Moreyra AE, Kostis JB, Kostis WJ; Myocardial Infarction Data Acquisition System (MIDAS 29) Study Group. Ischemic stroke rate increases in young adults: evidence for a generational effect? J Am Heart Assoc. 2016;5:e004245. doi: 10.1161/JAHA.116.004245.

4. Almekhlafi MA, Goyal M, Dippel DWJ, et al. Healthy Life-Year Costs of Treatment Speed From Arrival to Endovascular Thrombectomy in Patients With Ischemic Stroke: A Meta-analysis of Individual Patient Data From 7 Randomized Clinical Trials. JAMA Neurol. 2021;78(6):709–717. doi:10.1001/jamaneurol.2021.1055.

5. Mascia L, Del Sorbo L. Diagnosis and management of vasospasm. F1000 Med Rep. 2009;1. doi:10.3410/m1-33.

6. Kumar G, Shahripour RB, Harrigan MR. Vasospasm on transcranial Doppler is predictive of delayed cerebral ischemia in aneurysmal subarachnoid hemorrhage: A systematic review and meta-analysis. J Neurosurg. 2016.

7. Katsanos, A. H., Psaltopoulou, T., Sergentanis, T. N., Frogoudaki, A., Vrettou, A. R., Ikonomidis, I., … Tsivgoulis, G. (2016). Transcranial Doppler versus transthoracic echocardiography for the detection of patent foramen ovale in patients with cryptogenic cerebral ischemia: A systematic review and diagnostic test accuracy meta-analysis. Annals of Neurology, 79(4), 625–635.

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