Magnetic resonance angiography

Magnetic resonance angiography (MRA) uses magnetic resonance imaging to depict blood vessels and blood flow, with or without injected contrast agents.

Time-of-flight magnetic resonance angiography: An MRA technique that images flowing blood using signal differences between inflowing blood and stationary tissue. It depicts arteries without injected contrast by exploiting fresh blood entering an imaging slice.
Intracranial aneurysm: A localized abnormal dilation of an artery within the skull. MRA can screen for and follow many intracranial aneurysms without catheter angiography.
Nuclear magnetic resonance: A physical phenomenon in which atomic nuclei absorb and re-emit radiofrequency energy in a magnetic field. MRI signals underlying MRA arise from nuclear magnetic resonance, chiefly of hydrogen nuclei.
Digital subtraction angiography: An X-ray angiographic technique that subtracts pre-contrast images from images acquired after contrast injection. It offers detailed catheter-based vascular imaging and can permit treatment during the same procedure.
Phase-contrast magnetic resonance angiography: An MRA technique that encodes blood velocity in the phase of the MRI signal. It can map flow direction and quantify blood velocity as well as show vessels.
Carotid artery stenosis: Narrowing of one or both carotid arteries, usually caused by atherosclerotic plaque. Neck MRA can assess the location and severity of carotid narrowing.
Magnetic resonance signal: The radiofrequency signal emitted by excited nuclear spins as they return toward equilibrium in a magnetic field. MRA sequences manipulate this signal to distinguish blood from surrounding tissue.
Doppler ultrasonography: Ultrasound imaging that uses frequency shifts to assess blood movement and flow. It avoids ionizing radiation and contrast but depends more on acoustic access and operator technique.
Contrast-enhanced magnetic resonance angiography: An MRA technique that uses an injected paramagnetic contrast agent to improve vascular signal. Gadolinium-enhanced blood signal supports rapid imaging of broad vascular territories.
Peripheral artery disease: Reduced blood flow to the limbs, most often caused by atherosclerotic narrowing of peripheral arteries. MRA can map limb arteries when planning evaluation or revascularization.

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