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Updated: May 16, 2026
Functional Transcranial Doppler Ultrasound for Monitoring Cerebral Blood Flow
Published on: March 15, 2021
Transcranial Doppler velocities in a large, healthy population
Charles H Tegeler1, Kevin Crutchfield, Michael Katsnelson
1Wake Forest School of Medicine, Winston-Salem, NC, USA. ctegeler@wakehealth.edu
This study measured blood flow in the brain using a noninvasive technique called transcranial Doppler (TCD) in a large group of healthy people. Researchers found that blood flow speeds decrease with age, especially in Caucasians, and were generally higher in women than men. They also observed that pulsatility index (PI), which measures vascular resistance, increased with age in women but not consistently in men. The study provides reference values for blood flow and PI in different brain arteries across age, sex, and race groups. These values can help doctors identify abnormal TCD results that may indicate increased vascular risk. The authors suggest that more research is needed in diverse populations to better understand how brain blood flow varies across ethnic groups.
Area of Science:
- Neuroimaging techniques in cerebrovascular research
- Clinical hemodynamics within diagnostic radiology
Background:
Prior research has established transcranial Doppler (TCD) ultrasonography as a noninvasive method for measuring cerebral blood flow velocity. It has been used clinically since 1982 and is recognized for its safety and utility in cerebrovascular disease management. However, gaps remain in defining stable normal TCD values across diverse populations. Few recent studies have addressed this, and none have included a large cohort of healthy subjects representing a range of age, race, and gender. Automated tools for TCD interpretation are being developed, but they require standardized reference values for accurate comparisons. Existing data lack consistency in how variables like age, sex, and ethnicity influence TCD outcomes. This uncertainty has driven the need for a comprehensive study to define normal TCD values in a diverse, healthy population. Researchers aim to clarify how factors like age, gender, and race affect Doppler measurements. The absence of such data has limited the ability to interpret TCD results accurately in clinical settings. This study addresses that gap by examining a wide demographic range and identifying patterns in blood flow velocity and pulsatility index.
Purpose Of The Study:
The study aimed to define normal transcranial Doppler (TCD) values in a large, healthy population. It focused on measuring blood flow velocity and pulsatility index (PI) across various cerebral arteries. Researchers sought to determine how these values vary with age, sex, race, and other demographic factors. The motivation for this study was the lack of recent, comprehensive data on TCD reference values. Existing literature has not provided a detailed analysis of how age, gender, and ethnicity influence TCD outcomes. The study also aimed to assess the yield of usable data from different arterial segments. By establishing a reference population, the work supports the development of automated TCD interpretation tools. The ultimate goal is to provide a reliable baseline for identifying abnormal TCD values in clinical practice.
Main Methods:
The study enrolled 364 healthy subjects aged 18 to 80 years. Participants without cerebrovascular disorders or systemic conditions like hypertension or diabetes were included. Researchers recorded self-reported ethnicity, handedness, blood pressure, and BMI. A single sonographer performed all TCD examinations using a nonimaging device. The protocol standardized the assessment of up to 23 arterial segments. Automated waveform tracking calculated velocity and pulsatility index (PI) values. Data were analyzed for changes by decade of age, sex, race, handedness, BMI, and blood pressure. Descriptive statistics provided mean velocities and PI values across demographic groups.
Main Results:
Mean blood flow velocities (MBFV) were highest in the middle cerebral artery (MCA) and lowest in the posterior cerebral artery (PCA) across all groups. No significant differences were observed in MBFV between left and right segments of the Circle of Willis, except for the distal M1 and C1, which showed higher velocities on the left. Women had higher MBFV than men in all segments except the ophthalmic artery (OA). MBFV decreased with age in both men and women, but this trend was specific to Caucasians. Non-Caucasians showed lower velocities in the OA. Pulsatility index (PI) was lower in women than men for most segments and increased with age in women across all segments. This age-related PI increase was specific to Caucasians. The yield of usable data ranged from 99.7% in the vertebral artery (VA) and basilar artery (BA) to 88.2% in the C2 segment.
Conclusions:
The study provides normal TCD reference values for a large cohort of healthy subjects across age, sex, and race groups. Researchers observed decreased MBFV and increased PI with aging, particularly in Caucasians. Women had higher MBFV than men in most segments. Few differences in MBFV were found related to side or ethnicity, but changes in MBFV and PI with age were specific to Caucasians. The study reports mean and standard deviation values for MBFVs in key intracranial arteries. These data serve as a useful reference for identifying abnormal TCD values in clinical settings. The authors propose that TCD studies in large multiethnic populations are still required to better understand brain hemodynamics across different ethnic groups. The findings support the need for standardized reference values to improve the accuracy of TCD interpretation.
Frequently Asked Questions
The study found that mean blood flow velocities (MBFV) decreased with age, particularly in Caucasians, and were higher in women than men in most cerebral artery segments.
The study enrolled 364 healthy subjects aged 18 to 80 years with no known cerebrovascular disorders.
To ensure standardized and consistent measurements across all subjects and to minimize variability in data collection.
PI reflects vascular resistance and was found to increase with age in women and in some segments in men, primarily among Caucasians.
The yield of usable data for the VA was 99.7%, the highest among the arterial segments studied.
The authors propose that future TCD studies should include large multiethnic populations to better understand brain hemodynamics across different ethnic groups.
