Magnetic Resonance Angiography (MRA)

Magnetic resonance angiography is a kind of magnetic resonance imaging technique which uses a magnetic field and radio wave pulses to scan images of blood vessels inside the body. It is used to study blood flow and condition of blood vessels in key areas of the body like the brain, heart, lungs, kidneys, neck, abdomen, pelvis, etc. During the angiography, the portion of the body which is to be analyzed is placed inside a MRI machine. Any one of three imaging technologies can be used: magnetic resonance imaging (MRI), computed tomography (CT) or X-rays with catheters. MRA often uses a contrast material to produce clear images of blood vessels throughout the body. It is mainly used for the following reasons:

• It helps in identifying disease and aneurysms in the aorta or any other major blood vessel
• It detects atherosclerosis disease in the carotid artery of the neck, which restricts blood flow to the brain and hence, causes a stroke
• It samples blood from particular veins in the body to detect any form of endocrine disease
• It detects atherosclerotic disease which contracts arteries to the legs, and helps prepare for an endovascular intervention or surgery
• It indicates any disease in the renal artery, visualizes blood flow and helps in preparing for kidney transplant.

Procedure

Unlike CT scans and X-ray examinations, angiography does not depends on ionizing radiations. It uses a magnetic field and radio waves which are produced by passing an electric current through wire coils in MRI units. Testing is done on an outpatient basis where the patient has to lie down on a movable examination table. During imaging, straps and bolsters may be used to maintain the right position. Small devices containing coils, which are capable of transmitting and receiving radio waves, are placed around the patient's body. Contrast material, if needed, is injected intravenously into a vein on the patient's hand or arm. Contrast material helps define the blood vessels more clearly by making them look brighter. Once the examination is complete, the signals obtained are processed by a computer, which produces a series of images, each showing a thin slice of the body. These images are then evaluated from various angles by the physician.

Benefits

• Angiography almost eliminates the need for surgery, and in case surgery is needed, it can be done more accurately after this test
• It is a non-invasive imaging technique and hence, does not involve exposure to radiation
• Since no catheter is inserted in to the vein, there is no risk of damaging an artery or any other blood vessel
• MR angiography is safe, less time-consuming and more cost-effective
• It gives high-quality images of blood vessels even without using contrast material, hence, benefiting patients who are prone to allergic reactions

Risks and Limitations

• Magnetic resonance angiography poses almost no risk to the patient when necessary safety measures are followed
• Sometimes, if sedation is needed, there can be risk of excessive sedation
• MRA is not capable of capturing images of calcium deposits
• Some tests demand the patients to hold their breath for 15-20 seconds in order to get clear images. Patients who are not able to lie still or lie on their back for long may have poor quality images.

MRA normally includes multiple runs or sequences of tests and usually gets completed within 30 to 60 minutes. Patients can resume their usual activities and normal diet immediately after the exam.