Magnetic Resonance Imaging (MRI) is a diagnostic tool that produces highly detailed images of the body’s internal structures. Unlike X-rays or CT scans, MRI does not use ionizing radiation, relying instead on a powerful magnetic field and radio waves to create cross-sectional pictures. A brain MRI allows physicians to examine the soft tissues of the brain, useful for diagnosing conditions such as stroke, multiple sclerosis, or tumors. The addition of a contrast agent enhances the visibility of specific tissues and abnormalities, allowing for a clearer distinction between healthy and diseased tissue and improving diagnostic accuracy.
Preparing for Your MRI Brain Scan
Before the scan, a technician reviews a safety questionnaire regarding metal within your body. Due to the strong magnetic field, you must remove all external metallic items, including jewelry, watches, hearing aids, piercings, and items containing metal components like zippers or metallic makeup. You must also disclose any internal metal, such as aneurysm clips, pacemakers, cochlear implants, or shrapnel, as these can be affected by the magnet or interfere with image quality.
Preparation also involves discussing your medical history, particularly pre-existing kidney conditions. Since the contrast agent is filtered through the kidneys, patients with reduced kidney function may require specific safety considerations. If contrast is ordered, consent paperwork will be completed during this stage. You will typically change into a hospital gown to ensure no hidden metal interferes with imaging.
Understanding the Contrast Injection
The contrast agent used to enhance brain images is typically gadolinium, a rare earth metal. This agent alters the magnetic properties of water molecules in the tissues where it collects. When injected, the gadolinium-based agent shortens the time it takes for protons to return to their normal state, resulting in a brighter, more distinct signal on the final images.
The contrast agent is administered through an intravenous (IV) line, usually placed in a vein in your hand or arm, before or during the scan. Patients may report a temporary sensation of coolness at the injection site, a brief flush of warmth, or a metallic taste in the mouth immediately following the injection.
Gadolinium-based agents are generally safe, but kidney function screening is performed beforehand because the kidneys eliminate the agent. In patients with severe kidney disease, there is a very rare risk of nephrogenic systemic fibrosis (NSF) linked to certain types of gadolinium agents. Allergic reactions are also possible, ranging from mild symptoms like hives to more serious, immediate reactions.
What Happens During the Imaging Process
The imaging takes place inside a large, tube-shaped machine. You will lie on a padded table that slides into the center of the scanner, and your head is typically placed in a specialized coil designed to capture high-quality images of the brain. Remaining perfectly still throughout the procedure is necessary to prevent blurred images.
The scan usually takes between 30 and 60 minutes, with contrast adding a few extra minutes for administration and image acquisition. As the machine captures images, you will hear loud, repetitive mechanical noises, such as banging, clicking, or thumping. Earplugs or headphones are provided to minimize this noise and protect your hearing.
A technologist operates the scanner from an adjacent control room and maintains constant contact via an intercom system. You will be given a call button to press if you experience issues like anxiety or discomfort. For individuals with anxiety in enclosed spaces, the technologist may offer comfort strategies or, if prescribed by a physician, the option of a mild sedative.
After the Scan: Recovery and Results
After the scan is complete, the technologist removes the IV line used for the contrast injection. You can generally resume normal activities immediately, as no recovery period is required unless a sedative was administered. Drinking plenty of fluids is recommended afterward, as this helps flush the contrast agent out through the urinary system.
The captured images are sent to a radiologist, a physician specializing in interpreting medical images. The radiologist reviews the scan, both with and without contrast enhancement, to identify any abnormal findings. They compile a detailed report of their interpretation, which is sent to the ordering physician. Results for routine findings typically take a few days up to one or two weeks, while urgent cases are prioritized for a quicker turnaround.