Brain MRI & MRA

Overview

An MRI and an MRA are both noninvasive and painless diagnostic methods for seeing tissues, bones, and organs within the body. An MRI (magnetic resonance imaging) is a type of imaging that produces detailed pictures of organs and tissues. The emphasis of an MRA (magnetic resonance angiography) is on the blood arteries rather than the surrounding tissue.

Stroke, temporal lobe epilepsy, infection, inflammation, tumor, multiple sclerosis (MS), dementia, post-trauma, metabolic disorders, congenital malformations, internal auditory canal pathology, vascular pathology, pituitary fossa pathology, nerve palsies, and metabolic disorders are all conditions for which brain MRI is recommended. Stenosis/occlusion associated to stroke, or carotid stenosis, Dissection (a rupture in the artery wall that can induce stroke), or AVM's when brain MRA is recommended (arteriovenous malformations).

Foreign bodies, mechanical heart valves, surgical implants, plates, screws, staples, and clips, and metal-containing prosthetics, pacemakers, cochlear implants, drug infusion ports, insulin pumps, deep-brain stimulators, and other electrical devices, metal tooth implants and fillings are all contraindications to using brain MRI and MRA.

The dangers of MRIs and MRAs are comparable. If you require an intravenous contrast agent, there may be an additional risk involved with the injection. Other hazards include: body heating, radiofrequency skin burns, magnetic interactions from items within your body, and hearing impairment.

 

What is Brain MRI & MRA?

Brain MRI:

Magnetic resonance imaging (MRI) of the head is a painless, noninvasive technique that gives comprehensive pictures of your brain and brain stem. The pictures are produced by an MRI machine utilizing a magnetic field and radio waves. This procedure is also known as a brain MRI or a cranial MRI. You will travel to a hospital or radiology center to have a head MRI.

An MRI scan differs from a CT scan or an X-ray in that it does not create pictures using radiation. Because an MRI scan combines pictures to generate a 3-D view of your interior tissues, it is more successful than other scans at detecting abnormalities in microscopic brain regions like the pituitary gland and brain stem. To better view particular structures or abnormalities, a contrast agent, or dye, may be administered via an intravenous (IV) line.

 

Brain MRA:

Magnetic resonance angiography (MRA) is a series of procedures for visualizing blood arteries that use magnetic resonance imaging. Magnetic resonance angiography (MRA) is used to create pictures of arteries (and, less frequently, veins) in order to detect stenosis (abnormal narrowing), occlusions, aneurysms (vessel wall dilatations at danger of rupture), and other abnormalities.

 

Uses of Brain MRI & MRA

Indications for Brain MRI:

MR imaging of the head is used to diagnose a variety of sudden or chronic complaints. It can aid in the diagnosis of conditions such as:

• developmental anomalies.
• hydrocephalus — dilatation of fluid spaces within the brain (ventricles)
• hemorrhage in selected trauma patients.
• causes of epilepsy (seizure).
• brain tumors.
• certain chronic conditions, such as multiple sclerosis
• disorders of pituitary gland.
• disorders of the eye and inner ear.
• vascular problems, such as an aneurysm (a bubble-like expansion of the vessel), arterial occlusion (blockage) or venous thrombosis (a blood clot within a vein).

 

Indications for Brain MRA:

• MRA is used by doctors to detect anomalies,such as aneurysms, in the head and neck or other arteries.
• identify atherosclerotic (plaque) disease in the carotid artery in the neck, which might restrict blood flow to the brain and cause a stroke
• locate an arteriovenous malformation within the brain or elsewhere
• Guide interventional radiologists and surgeons on how to treat damaged blood arteries, such as implanting stents or assessing a stent after implantation.
• evaluate arteries feeding a tumor prior to surgery or other procedures such as chemoembolization or selective internal radiation therapy.
• evaluate stenosis and obstructions of vessels.
• detect injury to one or more arteries in the neck, or head following trauma.

 

Contraindications of Brain MRI & MRA

Brain magnetic resonance methods have minimal contraindications. Metals and electrical equipment should not be brought inside the scan room due to the intense magnetic fields, as they might pose a safety hazard and produce image artifacts. There is a possibility of creating movement or turning, producing heat or a current, or causing device malfunction. Furthermore, things might become projectiles or become caught in the mechanism.

The following are some items that might be contraindicated:

• Foreign bodies from trauma, mechanical heart valves, surgical implants, plates, screws, staples and clips, and prosthetics that contain metal.
• Metal tooth implants and fillings.
• Oxygen tanks, carts, chairs, IV poles, and other medical equipment.
• Pacemakers, cochlear implants, drug infusion ports, insulin pumps, deep-brain stimulators, and other electrical devices.
• Accessories such as keys, glasses, piercings, jewelry, hairpins, pagers, watches, wallets, identification badges, and pens.

Braces, intravascular stents and filters, surgical clips, staples, sutures, and orthopedic equipment are generally safe, especially if they are modern. However, these materials should be handled with caution, and the radiologist should be notified in order to detect any subsequent influence on the pictures.

Physical limitations that make supine lying impossible, such as severe respiratory distress or severe kyphosis or kyphoscoliosis, might make individuals unsuitable for an MRI. Obese people, for example, are unable to fit on the table or within the machine, which also limits MRI.

Patients who are unable to lie motionless, such as many children, those with mobility abnormalities, or those in extreme pain, may also be inappropriate for an MRI and may require sedation or general anesthesia. Those suffering from acute anxiety or claustrophobia, on the other hand, may require light sedation or anxiolytics.Because of its lengthy scan durations, MRI is also inappropriate for emergency circumstances unless absolutely essential.

While pregnancy is not a contraindication due to the lack of ionizing radiation, MRI should be used with caution. Contrast agents containing gadolinium can pass the placenta and should not be used, especially during the first trimester.

Contrast material is not indicated for use in patients with extensive renal insufficiency, whether acute or chronic; hence, other imaging modality other than MRI may be necessary.

 

MRI vs MRA

As previously stated, an MRA is a form of MRI, hence the two are extremely comparable. The main distinction between the two is what they are used to scan:

Similarities:

• Both are non-invasive tools used to diagnose disease and ailments
• Neither procedure uses radiation.

Differences:

• MRA is primarily used to look at blood vessels, while MRI can be used to look at various organs and tissues including the spine, joints, brain, and other internal organs.
• Using an MRI generally allows the radiologist to examine larger areas of the body.

 

Complications & Prevention

Patients with severe renal failure who receive gadolinium-based contrast agents are at risk of developing nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermatopathy (NFD). As a result, individuals with acute kidney injury (AKI) or chronic renal disease stage 4 or above (with an estimated glomerular filtration rate [GFR] of 30 mL/min/1.73 m2) should not receive contrast agents. Hepatorenal syndrome and a perioperative liver transplantation phase, in addition to end-stage renal disease, are risk factors for the development of NSF/NFD.

Patients with intermediate renal disease should be given contrast agents with caution, avoiding large doses, limiting the number of times contrast is given, and allowing for a substantial amount of time between successive scans. Gadodiamide, gadoversetamide, and gadopentetate dimeglumine should be avoided.

Caution should also be taken in patients with a history of allergies, as well as in children under the age of one year. Gadolinium contrast agents seldom cause allergic responses. More often than not, idiosyncratic responses occur.

The presence of intrathecal gadolinium on MRI of the brain exhibits distinctive characteristics and may simulate subarachnoid hemorrhage on susceptibility-weighted images. The detection of high-dose gadolinium in CSF spaces is required to avoid diagnostic and therapeutic problems.

 

How Should I Prepare?

You'll need to put on a hospital gown. This is done to avoid artifacts in the final photos and to comply with safety rules concerning the high magnetic field.

The rules for eating and drinking before an MRI differ depending on the test and facility. Unless your doctor instructs you differently, continue to eat and take your medications as normal.

An injection of contrast material is used in some MRI scans. If you have asthma or allergies to materials, medicines, food, or the environment, the doctor may inquire. Gadolinium, a contrast substance, is extensively used in MRI scans. Gadolinium contrast can be used in individuals who are allergic to iodine contrast. Gadolinium contrast is far less likely to cause adverse reactions than iodine contrast. Even if the patient is known to be allergic to gadolinium, it may be possible to utilize it following suitable pre-medication. Please see the ACR Manual on Contrast Media for additional information on allergic responses to gadolinium contrast.

Inform the technologist or radiologist of any major health issues or recent surgery. Some diseases, such as severe renal disease, may exclude you from receiving gadolinium safely. A blood test may be required to ensure that your kidneys are working appropriately.

If you suffer from claustrophobia (fear of enclosed spaces) or anxiety, ask your doctor to prescribe a moderate sedative before your assessment.

All jewelry and other items should be left at home or removed before to the MRI scan. Metal and technological goods are not permitted in the examination room. They can interfere with the MRI unit's magnetic field, cause burns, or become dangerous projectiles.

Inform the technologist whether you have any medical or electrical devices implanted in your body. These devices may disrupt the exam or represent a risk. Many implanted devices will come with a leaflet that explains the MRI hazards associated with that device.

Bring the pamphlet to the attention of the scheduler before the exam if you have it. MRI cannot be done unless the kind of implant and MRI compatibility are confirmed and documented. Bring any pamphlets you may have to your test in case the radiologist or technician has any questions.

Inform the technologist or radiologist whether you have any shrapnel, bullets, or other metal in your body. Foreign bodies close to, and especially stuck in, the eyes are particularly dangerous because they may move or heat up during the scan, causing blindness. Tattoo dyes may include iron and may heat up during an MRI scan. This is unusual. Tooth fillings, braces, eyeshadows, and other cosmetics are normally unaffected by the magnetic field. These objects, however, may alter photographs of the face or brain. Inform the radiologist of their existence.

 

What Happens During the Procedure?

Before certain MRIs, contrast dye will be injected into a vein in your arm or hand. This dye allows the doctor to examine structures inside your body more clearly. Gadolinium is a dye that is commonly used in MRIs. It may leave a metallic taste in your tongue.

You will be positioned on a table that glides inside the MRI machine. Straps may be used to keep you immobile during the exam. Your entire body may be within the machine. Alternatively, a portion of your body may remain outside the machine.

Inside your body, the MRI scanner generates a powerful magnetic field. A computer interprets the MRI data and generates a sequence of images. Each image depicts a tiny slice of your anatomy.

During the test, you may hear a loud pounding or tapping sound. This is the equipment that generates electricity in order to capture photographs within your body. To suppress the sound, you might request earplugs or headphones.

During the exam, you may experience twitching. This occurs as a result of the MRI stimulating nerves in your body. It's nothing to be concerned about.The MRI scan should take between 20 and 90 minutes.

 

How To Look at Brain MRI?

A radiologist, a professionally qualified doctor, will read the results of your MRI and submit the report to your doctor.

Your doctor will explain the significance of your test findings and what steps you should take next.

 

Benefits vs. Risks

Benefits:

• MRI is a noninvasive imaging technology that does not need radiation exposure.
• Without inserting an IV catheter into the blood vessels, detailed pictures of multiple blood vessels and blood flow may be acquired. When necessary, a tiny IV catheter is placed into a small vein in the arm to avoid injuring a major blood artery.
• An MRA scan may take less time than standard catheter angiography and does not require a recovery period, unless sedation is used. You may resume your usual daily activities immediately following the MRA exam if no anesthesia was utilized.
• The cost of MR angiography is cheaper than that of catheter angiography.
• MRA can generate helpful high-quality pictures of multiple blood arteries even when no contrast material is used. This makes it especially useful for people who are prone to allergic responses or have impaired kidney or liver function.
• The gadolinium contrast material used in MRIs is less likely to trigger an allergic reaction than iodine-based contrast materials used in x-rays and CT scans.

 

Risks:

• When acceptable safety requirements are followed, the MRI test provides essentially little danger to the ordinary patient.
• There is a danger of utilizing too much sedative if it is utilized. Your vital signs, however, will be monitored to reduce this danger.
• You will not be harmed by the powerful magnetic field. It may, however, cause implanted medical equipment to malfunction or distort visuals.
• Nephrogenic systemic fibrosis is a well-known consequence of gadolinium contrast injection. With the use of newer gadolinium contrast agents, it is quite rare. It frequently happens in persons who have severe renal disease. Before considering a contrast injection, your doctor will thoroughly evaluate your kidney function.
• An allergic reaction if your exam uses contrast material. Such reactions are usually mild and controlled by medication.

Despite the fact that there are no known health risks, data suggests that extremely minute levels of gadolinium can persist in the body, particularly the brain, after many MRI tests. This is particularly likely to happen in people who have repeated MRI tests throughout the course of their lives to monitor chronic or high-risk health issues. The contrast agent is largely excreted from the body via the kidneys. If you fall into this group, talk to your doctor about the likelihood of gadolinium retention, which varies from patient to patient.

According to IV contrast manufacturers, mothers should not breastfeed their babies for 24 to 48 hours after receiving contrast material. However, according to the most recent American College of Radiology (ACR) Manual on Contrast Media, studies reveal that the quantity of contrast absorbed by the newborn while nursing is exceedingly minimal.

 

Conclusion

Magnetic resonance imaging (MRI) of the head employs a powerful magnetic field, radio waves, and a computer to generate detailed images of the brain and other cranial structures that are clearer and more detailed than other imaging methods, whereas brain MRA employs the same technique but focuses on the vascular anatomy and structures.

An MRI of the head is used to diagnose a variety of sudden or chronic complaints. It can assist in the diagnosis of conditions such as developmental defects, stroke, brain tumors, certain chronic ailments such as multiple sclerosis, bleeding in selected trauma patients, and eye and inner ear problems. MRA, on the other hand, is used to identify vascular anomalies such as brain artery aneurysms.

Jewelry, watches, credit cards, and hearing aids are all susceptible to harm. All pins, hairpins, metal zippers, and other metallic things that might distort MRI pictures should be removed.