Getting an MRI: Your Complete Guide to What Happens and Why

Your doctor has ordered an MRI, and if you're like most people, you have questions. Maybe you've heard about the loud noises, the confined space, or the length of the scan, and you're feeling apprehensive. Perhaps you're wondering why your doctor chose MRI over a CT scan or X-ray, or what happens after the images are taken.

Magnetic resonance imaging is one of the most powerful diagnostic tools in modern medicine, capable of producing extraordinarily detailed images of soft tissues, organs, and structures that other imaging modalities simply cannot match. Understanding how MRI works, what the experience is actually like, and how to prepare can transform the scan from a source of anxiety into a manageable — even interesting — medical experience.

How MRI Technology Works

An MRI scanner uses an extremely powerful magnet — typically 1.5 to 3 Tesla, which is 30,000 to 60,000 times stronger than Earth's magnetic field — to align hydrogen atoms in your body. When radio frequency pulses are directed at these aligned atoms, they briefly absorb energy and then release it as they return to their resting state. Sensitive receivers in the scanner detect these energy signals, and a computer translates the data into detailed cross-sectional images.

Because different tissues contain different amounts of water (and therefore hydrogen), they produce different signal intensities. This is what makes MRI exceptionally good at distinguishing between types of soft tissue — it can differentiate between healthy and diseased tissue, identify inflammation, detect tumors, visualize ligament tears, and map brain structures with remarkable precision.

Unlike CT scans and X-rays, MRI does not use ionizing radiation. This makes it particularly valuable for situations requiring repeated imaging (monitoring chronic conditions), imaging children, and evaluating the brain and spinal cord. The absence of radiation risk is one of MRI's significant advantages over other imaging modalities.

What MRI Scans Are Used For

Brain and spinal cord imaging is one of MRI's most common applications. It can detect tumors, stroke damage, multiple sclerosis lesions, aneurysms, spinal cord compression, and traumatic brain injuries with unmatched detail. Functional MRI (fMRI) can even map brain activity by detecting changes in blood flow during specific tasks.

Musculoskeletal MRI excels at visualizing joints, tendons, ligaments, and cartilage. It's the imaging standard for diagnosing ACL tears, meniscus injuries, rotator cuff damage, and herniated discs. Unlike X-rays, which only show bone, MRI reveals the full spectrum of soft tissue structures surrounding a joint.

Abdominal and pelvic MRI evaluates organs including the liver, kidneys, pancreas, uterus, ovaries, and prostate. MRI is increasingly used for cancer staging and for evaluating complex anatomical questions that CT alone cannot answer. Cardiac MRI provides detailed views of heart structure and function, including the ability to characterize heart muscle tissue and identify areas of scarring or inflammation.

Preparing for Your MRI

Preparation for most MRI scans is straightforward. You'll be asked to remove all metal objects — jewelry, watches, hair clips, belt buckles, and piercings — because the powerful magnet can attract ferrous metals with dangerous force. You'll change into a hospital gown to ensure no hidden metal fasteners, zippers, or underwire bras interfere with the scan.

Before the scan, you'll complete a safety screening questionnaire about any metal in your body. Certain metallic implants — some older pacemakers, certain cochlear implants, metal shrapnel, and some aneurysm clips — are absolute contraindications to MRI. Modern joint replacements, most dental work, and newer pacemakers are generally MRI-safe, but the radiology team must verify each case individually.

For some scans, you may receive a contrast agent called gadolinium, injected through an IV line. Gadolinium enhances the visibility of certain structures, particularly blood vessels, tumors, and areas of inflammation. It's generally well tolerated, though people with severe kidney disease may need alternative imaging due to a rare complication called nephrogenic systemic fibrosis.

Most MRI scans don't require fasting, though abdominal MRIs may require you to avoid eating for several hours beforehand. Your radiology center will provide specific instructions when you schedule your appointment.

What the Scan Experience Is Like

You'll lie on a motorized table that slides into the MRI bore — the cylindrical opening in the center of the machine. Standard bore sizes are about 60 centimeters (24 inches) in diameter, which can feel tight for larger patients or those with claustrophobia. Open MRI machines, which have wider openings or are open on the sides, are available at many facilities and are an option for claustrophobic patients, though image quality may be slightly lower.

The scan itself is painless. You won't feel the magnetic field or radio waves. What you will notice is noise — MRI machines produce loud knocking, buzzing, and humming sounds as the magnetic gradient coils switch on and off. These sounds can reach 100 decibels or more, which is why you'll be given earplugs or noise-canceling headphones. Many facilities offer music through MRI-compatible headphones to help pass the time.

Remaining still is crucial for image quality. Even small movements can blur the images and potentially require sequences to be repeated, extending scan time. You'll be instructed to stay as still as possible, and for certain sequences, you may be asked to hold your breath briefly. A technologist will communicate with you through an intercom throughout the scan, and you'll have a squeeze ball to signal if you need to stop.

Scan duration varies by body part and clinical question. A focused knee MRI might take 20 to 30 minutes, while a comprehensive brain study or multi-region scan can take 45 to 75 minutes. Your appointment time will include check-in, preparation, and the scan itself — plan for 60 to 90 minutes total.

Managing Claustrophobia

Claustrophobia during MRI is common — estimates suggest 5 to 15 percent of patients experience significant anxiety, and 1 to 2 percent cannot complete a standard closed MRI scan without intervention. If you're prone to claustrophobia, several strategies can help.

Talk to your doctor about mild sedation before the scan. A short-acting benzoyl diazepine like lorazepam can significantly reduce anxiety. If prescribed, you'll need someone to drive you home afterward. Some patients find that simply closing their eyes before entering the bore and keeping them closed throughout the scan is sufficient — if you can't see the enclosed space, claustrophobic responses are less likely to trigger.

Progressive muscle relaxation and focused breathing techniques practiced before the appointment can provide in-scan coping tools. Visualizing a calming scene — a beach, a garden, a favorite memory — while breathing slowly can make the experience significantly more manageable. Most facilities also place a mirror or prism on the head coil that allows you to see out of the bore, which some patients find reassuring.

After the Scan: Results and Follow-Up

After your scan, a radiologist — a physician specializing in medical imaging — will analyze the images and generate a written report for your ordering physician. Turnaround time varies: emergency MRIs are typically read within hours, while routine outpatient scans may take 24 to 72 hours for the report to reach your doctor.

Your ordering physician will review the results with you, explain any findings, and discuss next steps. Don't panic if the radiologist notes "incidental findings" — these are abnormalities discovered that weren't the reason for the scan. Many incidental findings are benign (small cysts, minor degenerative changes) and require no treatment, though some may warrant follow-up imaging or evaluation.