A magnetic resonance angiography (MRA) is an invasive medical test which helps doctors or physicians diagnose and examine different medical conditions. It provides information which sometimes can’t be obtained through an ultrasound, X-ray, or computed tomography (CT) scan.
Angiography is an imaging technique used to visualize the vital organs inside the body. Magnetic Resonance Angiography (MRA) is one of the imaging techniques that is used to visualize the flow of blood and the condition of blood vessels. 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.
By using MRA we can examine areas like;
- Arteries of neck
- Arteries of brain
- Abdominal aorta
- Renal arteries
However, for the evaluation of coronary arteries, CT scan is preferred over MRA.
There are three types of MRI namely;
- Time of Flight Angiography (TOF): This technique explores the physical properties of the blood and make the blood vessels appear bright in the images that are recorded.
- Phase Contrast Angiography (PCA): With the help of the properties of blood, the vessel images appear bright in the images.
- Contrast Enhanced Angiography (CE): It gives a clearer image by using the sequence of blood that causes the vessels to look brighter.
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.
Unlike CT scans and X-ray examinations, angiography does not depend on ionizing radiations. In the MRA scanner, there are inbuilt devices. These devices contain coils, which are capable of transmitting and receiving radio waves. The coils are located in such a manner that images of blood vessels of any part of the body can be recorded.
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. The devices are placed around the patient’s body. The coils in the devices are excited by the passing of electric current. Due to the magnetic nature of the coils, they create a magnetic field. The radio waves are generated and received by the coils that are below the part of the body, the image of which is to be obtained.
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. It creates a soft tissue contrast between blood vessels and the surrounding primary tissues created by flow, thus highlighting the required vessel. These images are then evaluated from various angles by the physician. If the physician wants a clearer image of the vessel, then a contrast material is used. Using the material, makes the vessel appear white in the image. Generally, the contrast material used are Iodine, Barium and Gadolinium.
There are two types of MRA imaging types namely;
- Black Blood MRA: It is used to perform cardiac chamber segmentation by reducing the signal from the blood.
- Bright Blood MRA: It makes the blood vessel look brighter by suppressing the background tissues and highlighting the softer tissues.
- Though the test does not require any pre-test preparation, the doctor generally recommends to avoid consumption of food 4-5 hours before the test. This is done, just to make sure that there are no disturbances in the image.
- If the patient has a pacemaker installed or has had any major surgeries, then the doctor should be informed beforehand. This is because the presence of the metallic objects can interrupt the magnetic field and false images can be created.
- The patient is told to change into the hospital gown and remove any piece of jewelry or any metallic objects that they have.
- If the patient is anxious or scared about the procedure, then sedatives are given to limit their motion.
- The patient is asked to lie down on the machine. In case the patient is claustrophobic or is overweight, open MRA machines are used.
- Next, the machine is started and due to the electric current the coils are magnetized and the radio signals are generated.
- These signals create 2D and 3D images of the vessel that is to be examined.
- Then the images are viewed on the television screen.
- In case, the images need to be clearer, content material can be used to highlight the vessel.
The images are instantly obtained, within a few minutes after the test.
- If the results show some abnormality, it can generally beatherosclerosis (hardening of the artery). The doctor can suggest some medicines or conduct further tests, to be reassured before suggesting any surgery.
- And if the results are normal, they suggest that there are no blockages in the arteries.
The results thus obtained can help in detecting:
- Fat Deposits
- Calcium Deposits
- Tear in the Aorta
- Stenosis of the Blood Vessels of the Lungs, Kidneys and Legs.
Once the entire process is completed and the images are obtained, the patient can go home. This is the advantage of MRA over the conventional angiography techniques. However, if the patient is under the influence of medicine, then rest is advised, till the time the patient gains consciousness.
Magnetic Resonance Angiography is advantageous over the conventional one, in many ways.
- Non Usage of Catheters: This is the biggest advantage of MRA. No needles are injected for obtaining the images.
- Radiation Free: Patients are not exposed to any kind of radiations during the test.
- Non-Allergic: As there are no chemicals involved in this procedure, there is very little chance of the patient contracting any allergy.
- Elimination of Surgery: Angiography almost eliminates the need for surgery, and in case surgery is needed, it can be done more accurately after this test.
However, the technique also has some drawbacks.
- Cost: Out of all the techniques available, MRA is considered to be the costliest.
- Spatial Resolution: Images that are obtained have limitation regarding the resolution. Blurring of the images can take place if the resolution is changed.
- Time-consuming: In some cases the time of the test can be almost an hour.
- Use of Sedatives: Sometimes, if sedation is needed, there can be risk of excessive sedation.
- Presence of Metallic Objects: In case patients have pacemakers and joints in the body that are metallic, the test cannot be performed. In such cases, ultrasound is preferred.
- Patient Mobility: As the patient is not injected during the process, slight movement can hamper the quality of the image and the test has to be repeated.
- Calcium Deposits: MRA is not capable of capturing images of calcium deposits.
The average cost of MRI is $600 to $1000 which is costlier than the other scanning techniques. Magnetic Resonance Technique is a part of the MRI procedure. The images obtained help the doctor in planning the surgery by providing the exact position of the defect. 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.