Time of flight angiography
Citation, DOI, disclosures and article data
At the time the article was created Usman Bashir had no recorded disclosures.
View Usman Bashir's current disclosuresAt the time the article was last revised Amanda Er had no financial relationships to ineligible companies to disclose.
View Amanda Er's current disclosures- Time of flight angiography (TOF)
- Time of flight (TOF) angiography
- Time-of-flight angiography
Time of flight angiography (TOF) is an MRI technique to visualize flow within vessels, without the need to administer contrast. It is based on the phenomenon of flow-related signal hyperintensity of spins entering into an imaging slice. As a result of being unsaturated, these spins give more signal than surrounding stationary spins.
With 2-D TOF, multiple thin imaging slices are acquired with a flow-compensated gradient-echo sequence. These images can be combined by using a technique of reconstruction such as maximum intensity projection (MIP), to obtain a 3-D image of the vessels analogous to conventional angiography.
With 3-D TOF, a volume of images is obtained simultaneously by phase-encoding in the slice-select direction. An angiographic appearance can be generated using MIP, as is done with 2-D TOF.
Key points
short TR
image-plane kept perpendicular to flow direction
Potential pitfalls
slow flow or flow from a vessel parallel to the scan plane may become saturated just like stationary tissue, resulting in a signal loss from the vessel 4
turbulent flow may undergo spin-dephasing and unexpectedly short T2 relaxation: again resulting in a signal loss from the vessel
acquisition times are relatively long (more than 5 minutes) 3.
retrograde arterial flow may be obscured if venous saturation bands have been applied.
artifacts: ghosting, susceptibility artifact
very T1 bright signal will be visible, e.g. hemorrhage
Quiz questions
References
- 1. McRobbie DW. MRI from picture to proton. Cambridge Univ Pr. (2003) ISBN:0521523192. Read it at Google Books - Find it at Amazon
- 2. Stepansky F, Hecht EM, Rivera R et-al. Dynamic MR angiography of upper extremity vascular disease: pictorial review. Radiographics. 28 (1): e28. doi:10.1148/radiol.e28 - Pubmed citation
- 3. Wheaton A & Miyazaki M. Non-Contrast Enhanced MR Angiography: Physical Principles. J Magn Reson Imaging. 2012;36(2):286-304. doi:10.1002/jmri.23641 - Pubmed
- 4. Edelman R & Koktzoglou I. Noncontrast MR Angiography: An Update. J Magn Reson Imaging. 2018;49(2):355-73. doi:10.1002/jmri.26288 - Pubmed
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