Skip to main content
Advertisement

Main menu

  • Home
  • Content
    • Current Issue
    • Publication Preview--Ahead of Print
    • Past Issue Archive
    • Case of the Week Archive
    • Classic Case Archive
    • Case of the Month Archive
    • COVID-19 Content and Resources
  • For Authors
  • About Us
    • About AJNR
    • Editors
    • American Society of Neuroradiology
  • Submit a Manuscript
  • Podcasts
    • Subscribe on iTunes
    • Subscribe on Stitcher
  • More
    • Subscribers
    • Permissions
    • Advertisers
    • Alerts
    • Feedback
  • Other Publications
    • ajnr

User menu

  • Subscribe
  • Alerts
  • Log in

Search

  • Advanced search
American Journal of Neuroradiology
American Journal of Neuroradiology

American Journal of Neuroradiology

  • Subscribe
  • Alerts
  • Log in

Advanced Search

  • Home
  • Content
    • Current Issue
    • Publication Preview--Ahead of Print
    • Past Issue Archive
    • Case of the Week Archive
    • Classic Case Archive
    • Case of the Month Archive
    • COVID-19 Content and Resources
  • For Authors
  • About Us
    • About AJNR
    • Editors
    • American Society of Neuroradiology
  • Submit a Manuscript
  • Podcasts
    • Subscribe on iTunes
    • Subscribe on Stitcher
  • More
    • Subscribers
    • Permissions
    • Advertisers
    • Alerts
    • Feedback
  • Follow AJNR on Twitter
  • Visit AJNR on Facebook
  • Follow AJNR on Instagram
  • Join AJNR on LinkedIn
  • RSS Feeds
LetterLetter

Flow voids in Time-of-Flight MR Angiography of Carotid Artery Stenosis? It Depends on the TE!

Michael H. Lev, Javier M. Romero and R. Gilberto Gonzalez
American Journal of Neuroradiology November 2003, 24 (10) 2120;
Michael H. Lev
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Javier M. Romero
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
R. Gilberto Gonzalez
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • Article
  • Info & Metrics
  • References
  • PDF
Loading

Nederkoorn et al (1) conclude that flow voids on nonenhanced 3D time-of-flight (TOF) MR angiography (MRA) images represent severe carotid artery stenosis. Although they present compelling evidence that this conclusion is correct for their particular MR imaging system with their particular imaging parameters, radiologists should be advised of the peril of generalizing these results to any MR imaging system, using any imaging parameters. Specifically, preliminary data from our neurovascular lab suggest that the presence of flow voids on 2D TOF MRA images, for a given degree of carotid artery narrowing, is critically dependent on choice of echo time (TE) for the TOF pulse sequence, specific MR imaging hardware, or both.

In a pilot study of patients who underwent both carotid duplex sonography and 2D TOF MRA for evaluation of suspected internal carotid artery stenosis, 20 were imaged on a newer LX unit (GE Medical Systems, Milwaukee, WI) by using a short-TE pulse sequence (TE ≈4.7 ms), and 24 were imaged on an older Signa unit (GE Medical Systems) by using a long-TE pulse sequence (TE ≈8.7 ms). Of the 20 imaged with the short-TE pulse sequence, TOF signal dropout was seen in one (100%) of one with hairline lumen, in three (50%) of six with peak systolic velocity (PSV) more than 400 cm/s, in four (50%) of eight with PSV between 200 and 400 cm/s, and in none (0.0%) of three with PSV less than 200 cm/s (two patients with PSV’s of ∼370 and 540 cm/s had equivocal signal dropout). Of the 24 imaged with the long-TE pulse sequence, TOF signal dropout was seen in one (100%) of one with hairline lumen, in 10(100%) of 10 with PSV more than 400 cm/s, in four (80%) of five with PSV between 200 and 400 cm/s, and in one (14.3%) of seven with a PSV less than 200 (one patient with PSV ∼300 cm/s had equivocal signal dropout). One patient was imaged twice, each imaging session a week apart without interval treatment, by using different TE values. The first images, which were obtained with a long TE of 8.6 ms, showed a flow void, whereas the follow-up images, which were obtained with a short TE of 4.7 ms, did not.

These findings are consistent with the fact that flow voids on TOF MRA images are caused by intravoxel dephasing and are thus less likely to occur with short than with long TEs. Additionally, the stronger gradients and more homogeneous magnetic fields present in newer MR units, which permit smaller voxel sizes, may also predispose to decreased intravoxel dephasing, and hence lower sensitivity for signal dropout from turbulent flow. Although, as Nederkoorn et al point out, 3D TOF MRA techniques “have higher spatial resolution, a greater signal-to-noise ratio, and lower sensitivity for voids because of the smaller voxels and shorter echo time(s)” as compared with those of 2D TOF MRA, the precise relationship between 3D TOF flow void detection thresholds and the specific MR imaging hardware and software used has yet to be determined. Until it has, we continue to advise a conservative approach to flow void interpretation on TOF MRA images. Indeed, radiologists ideally should calibrate TOF signal dropout for their particular MR units and pulse sequences with an external reference standard of stenosis, such as sonography or CTA, before image interpretation. This may be especially prudent in some clinical environments wherein surgeons consider patients with carotid artery flow voids to have “proved” severe (>70%) lumenal stenosis, and therefore to be candidates for carotid endarterectomy.

References

  1. ↵
    Nederkoorn PJ, van der Graaf Y, Eikelboom BC, et al. Time-of-Flight MR Angiography of Carotid Artery Stenosis: Does a Flow Void Represent Severe Stenosis? AJNR Am J Neuroradiol 2002;23:1779–1784
    Abstract/FREE Full Text
  • Copyright © American Society of Neuroradiology
PreviousNext
Back to top

In this issue

American Journal of Neuroradiology: 24 (10)
American Journal of Neuroradiology
Vol. 24, Issue 10
1 Nov 2003
  • Table of Contents
  • Index by author
Advertisement
Print
Download PDF
Email Article

Thank you for your interest in spreading the word on American Journal of Neuroradiology.

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
Flow voids in Time-of-Flight MR Angiography of Carotid Artery Stenosis? It Depends on the TE!
(Your Name) has sent you a message from American Journal of Neuroradiology
(Your Name) thought you would like to see the American Journal of Neuroradiology web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Citation Tools
Flow voids in Time-of-Flight MR Angiography of Carotid Artery Stenosis? It Depends on the TE!
Michael H. Lev, Javier M. Romero, R. Gilberto Gonzalez
American Journal of Neuroradiology Nov 2003, 24 (10) 2120;

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero
Share
Flow voids in Time-of-Flight MR Angiography of Carotid Artery Stenosis? It Depends on the TE!
Michael H. Lev, Javier M. Romero, R. Gilberto Gonzalez
American Journal of Neuroradiology Nov 2003, 24 (10) 2120;
Reddit logo Twitter logo Facebook logo Mendeley logo
  • Tweet Widget
  • Facebook Like
  • Google Plus One

Jump to section

  • Article
    • References
  • Info & Metrics
  • References
  • PDF

Related Articles

  • No related articles found.
  • PubMed
  • Google Scholar

Cited By...

  • Contrast-Enhanced MR Angiography Is Not More Accurate Than Unenhanced 2D Time-of-Flight MR Angiography for Determining >=70% Internal Carotid Artery Stenosis
  • Crossref
  • Google Scholar

This article has not yet been cited by articles in journals that are participating in Crossref Cited-by Linking.

More in this TOC Section

  • Fair Performance of CT in Diagnosing Unilateral Vocal Fold Paralysis
  • Reply:
  • Regarding “Altered Blood Flow in the Ophthalmic and Internal Carotid Arteries in Patients with Age-Related Macular Degeneration Measured Using Noncontrast MR Angiography at 7T”
Show more LETTERS

Similar Articles

Advertisement

News and Updates

  • Lucien Levy Best Research Article Award
  • Thanks to our 2022 Distinguished Reviewers
  • Press Releases

Resources

  • Evidence-Based Medicine Level Guide
  • How to Participate in a Tweet Chat
  • AJNR Podcast Archive
  • Ideas for Publicizing Your Research
  • Librarian Resources
  • Terms and Conditions

Opportunities

  • Share Your Art in Perspectives
  • Get Peer Review Credit from Publons
  • Moderate a Tweet Chat

American Society of Neuroradiology

  • Neurographics
  • ASNR Annual Meeting
  • Fellowship Portal
  • Position Statements

© 2023 by the American Society of Neuroradiology | Print ISSN: 0195-6108 Online ISSN: 1936-959X

Powered by HighWire