Magnetic resonance angiography
Last reviewed: 23.04.2024
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Magnetic resonance angiography (MP-angiography), in contrast to spiral CT, conventional and digital subtraction angiography, allows visualization of blood vessels even without the use of contrast media. The study can be carried out in 2D or 3D modes.
MP-methods of visualization of 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;
- MR angiography with contrast enhancement [Contrast Enhanced (CE) MRAJ.
Methods of phase-contrast MP-angiography allow you to visualize the flow of blood in the plane of the cut, map the rate of movement of blood and measure the rate of blood flow. The merits of phase methods include the fact that the phase encoding of the speed of motion is produced in any direction, including in the plane of the cut, which can be very thin. Phase-contrast MRI is applicable for visualization of rapid arterial blood flow (with an encoding equal to 80 cm / s), slow venous blood flow and slow movement of cerebrospinal fluid (coding 10-20 cm / s). In clinical conditions, they are most often used as a supplement to time-of-flight MR angiography in order to distinguish stationary areas with high MP signal in T1 mode (for example, subacute hematoma) and real moving blood in a vessel or with MP-liquorography.
MP angiography with contrast enhancement uses the shortening of T1 under the action of magnetic resonance contrast preparations. Contrast substance is administered intravenously, data registration begins at the moment of filling the test vessel with contrast medium. To determine the optimal time of registration, a preliminary bolus injection of 1-2 ml of a contrast preparation is carried out, determining the moments of the onset of the arterial and venous phases of the blood flow in order to carry out subsequent measurements at the peak of the arterial concentration of the contrast medium. In modern MP scanners, a bolus test is performed automatically, which shortens the scan time to 1 minute as a whole. MP-angiography with contrast enhancement is used to obtain an image of the main arteries from the arch of the aorta to the Willis circle or veins of intracranial localization. Methods of parallel scanning promise to shorten the time of vascular examination to 2.5-3 s - MP-angiography in real time.
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