What is the role of 3D time-of-flight (TOF) MRA in acute stroke imaging?

Updated: Dec 09, 2020
  • Author: Souvik Sen, MD, MPH, MS, FAHA; Chief Editor: Helmi L Lutsep, MD  more...
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The three-dimensional (3D) time-of-flight (TOF) technique is based on flow-related enhancement; it is the preferred MRA technique. However, it has some limitations, especially flow signal dropout secondary to turbulent flow in the tortuous and stenotic vascular segments, which makes interpretation of stenosis in these areas difficult. These are common predilection sites for atherosclerosis. In addition, in slow-flow regions, the spin saturation of the scan causes overestimation of stenosis. In contrast-enhanced studies, it provides more information than standard angiography, especially in detecting critical stenosis of extracranial vessels, but it is less reliable in intracranial critical stenosis. Always keep in mind that MRA is a flow-dependent technology; absence of flow signal does not mean literally a complete occlusion but rather that flow is below a critical value.

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