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Magnetic resonance angiography
Last reviewed: 07.07.2025
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Magnetic resonance angiography (MR angiography), unlike spiral CT, conventional and digital subtraction angiography, allows visualization of blood vessels even without the use of a contrast agent. The study can be performed in 2D or 3D modes.
MR methods for visualizing moving fluid (blood) are divided into three categories:
- time-of-flight MR angiography - TOF (Time of Flight), or T1 angiography;
- phase-contrast MR angiography - PC (Phase Contrast), or T2 angiography;
- Contrast Enhanced (CE) MRAJ.
Phase-contrast MR angiography methods allow visualization of blood flow in the slice plane, mapping of blood velocity and measurement of blood flow velocity. The advantages of phase methods include the fact that phase encoding of the velocity of movement is performed in any direction, including in the slice plane, which can be very thin. Phase-contrast MRI is applicable for visualization of fast arterial blood flow (with encoding equal to 80 cm/s), slow venous blood flow and slow movement of cerebrospinal fluid (encoding 10-20 cm/s). In clinical conditions, it is most often used as an addition to time-of-flight MR angiography in order to delineate stationary areas with a high MR signal in T1 mode (for example, subacute hematoma) and really moving blood in a vessel or during MR cerebrospinal fluidography.
Contrast-enhanced MR angiography uses T1 shortening caused by magnetic resonance contrast agents. The contrast agent is administered intravenously, and data recording begins when the vessel being examined is filled with the contrast agent. To determine the optimal recording time, a preliminary bolus injection of 1-2 ml of the contrast agent is performed, determining the moments of the onset of the arterial and venous phases of blood flow in order to perform subsequent measurements at the peak of the arterial concentration of the contrast agent. In modern MR tomographs, the bolus test is performed automatically, which reduces the scanning time to 1 min in total. Contrast-enhanced MR angiography is used to obtain an image of the main arteries from the aortic arch to the circle of Willis or veins of intracranial localization. Parallel scanning methods promise to reduce the time of vascular examination to 2.5-3 s - real-time MR angiography.
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