Angio-magnetic resonance imaging (synonyms: Angio-MRI; nuclear magnetic resonance imaging (NMR) of the vessels; MRI vessels; MRI angio; MR angiography (MRA); vascular imaging by magnetic resonance imaging) refers to a radiological examination procedure in which a magnetic field is used to image the vessels. With this examination method, targeted images of the vessels of various body regions are possible, such as the brain, thorax, abdomen (abdominal cavity), pelvis, extremities (arms or legs). Vascular imaging in magnetic resonance imaging (MRI) is possible without contrast medium, but a better informative value can be achieved under injection of a contrast medium, Magnetic resonance imaging of the vessels is a very precise diagnostic procedure that is used today for many diseases and complaints.
Indications (areas of application)
- Aneurysm – outpouching of blood vessels.
- Vascular changes or abnormalities [e.g., angiomas (vascular tumors)]
- Vascular occlusions or stenoses (narrowing in the vessels).
- Representation of collateral circuits (bypass circuits).
- Venous thrombosis, especially in the brain or abdominal vessels, as well as vessels of the extremities (arm or leg)
- Pulmonary embolism – occlusion of one or more pulmonary vessels.
Contraindications
The usual contraindications apply to angio-MRI as to any MRI examination:
- Cardiac pacemakers (with exceptions).
- Mechanical artificial heart valves (with exceptions).
- ICD (implanted defibrillator)
- Metallic foreign body in dangerous localization (e.g., in close proximity to vessels or eyeball)
- Other implants such as: Cochlear/ocular implant, implanted infusion pumps, vascular clips, Swan-Ganz catheters, epicardial wires, neurostimulators, etc.
Contrast administration should be avoided in cases of severe renal insufficiency (renal impairment) and existing pregnancy.
The procedure
Magnetic resonance imaging is one of the non-invasive, that is, not penetrating into the body, imaging procedures.By using the magnetic field, protons (mainly hydrogen) are excited in the body to nuclear magnetic resonance. This is a change in the orientation of the particle due to a magnetic field. This is picked up as a signal via the coils set up around the body during the examination and sent to the computer, which calculates the exact image of the body region from the many measurements that take place during an examination.In these images, the differences in the shades of gray thus arise from the distribution of the hydrogen ions.In MRI, one can distinguish between different imaging techniques, such as T1-weighted and T2-weighted sequences.MRI offers very good imaging of soft tissue structures. In angio-MRI, the patient is injected intravenously with a contrast agent during the examination.Thus, the radiologist can obtain even more detailed findings about any disease processes present in the area of the vessels through this examination. The contrast medium is a paramagnetic substance (it is not a contrast medium containing iodine). The examination usually takes about half an hour and is performed while the patient is lying down. During the examination, the patient is in a closed room in which a strong magnetic field prevails.Since the MRI machine is relatively loud, headphones are put on the patient.Especially during examinations of the head, claustrophobia (fear of space) can occur, since the head then lies in a coil. Magnetic resonance imaging of the vessels is a very precise diagnostic procedure that is used today for many diseases and conditions.
Possible complications
Ferromagnetic metal bodies (including metallic makeup or tattoos) can lead to local heat generation and possibly cause paresthesia-like sensations (tingling). Allergic reactions (up to life-threatening, but only very rare anaphylactic shock) may occur due to contrast medium administration. The administration of a contrast medium containing gadolinium can also trigger nephrogenic systemic fibrosis in rare cases.
