An MRI scan uses magnets and radio waves to capture images inside your body without making a surgical incision. The scan allows your doctor to see the soft tissue of your body, like muscles and organs, in addition to your bones.
An MRI can be performed on any part of your body. A lumbar MRI specifically examines the lumbar section of your spine — a region where back problems commonly originate.
The lumbosacral spine is made up of the five lumbar vertebral bones (L1 thru L5), the sacrum (the bony “shield” at the bottom of your spine), and the coccyx (tailbone). In addition to bones, the lumbosacral spine consists of large blood vessels, nerves, tendons, ligaments, and cartilage.
Your doctor may recommend an MRI to better diagnose or treat problems with your spine. Your condition could be caused by injury-related pain, disease, infection, or other factors. Your doctor might order a lumbar MRI if you have the following symptoms:
- back pain accompanied by fever
- birth defects affecting your spine
- injury to your lower spine
- persistent or severe lower back pain
- multiple sclerosis
- problems with your bladder
- signs of brain or spinal cancer
- weakness, numbness, or other problems with your legs
Your doctor might also order a lumbar MRI if you’re scheduled for spinal surgery so that they can plan the procedure before making an incision.
An MRI scan provides a different kind of image from other imaging tests, such as an X-ray, ultrasound, or CT scan. An MRI of the lumbar spine shows the bones, disks, and spinal cord, as well as the spaces between the vertebral bones where nerves pass through.
Unlike an X-ray or CT scan, an MRI doesn’t use ionizing radiation. It’s considered a safer alternative for people, especially pregnant women and growing children. Although side effects do sometimes occur, they’re extremely rare. There have been no documented side effects from the radio waves and magnets used in the scan to date.
However, there are risks for those who have implants containing metal. The magnets used in an MRI can result in problems with pacemakers or cause implanted screws or pins to shift in your body.
One complication that can also arise is an allergic reaction to contrast dye. During some MRI examinations, contrast dye is injected into the bloodstream to provide a clearer image of blood vessels in the area being scanned. The most common type of contrast dye is gadolinium. While resulting allergic reactions are often mild and easily controlled by medication, occasional anaphylactic reactions (and even deaths) have been reported.
Before the test, tell your doctor if you have a pacemaker. Depending on the type of pacemaker, your doctor may suggest another method for inspecting your lumbar spine, such as a CT scan. However, some pacemaker models can be reprogrammed before an MRI so they’re not disrupted during the examination.
Because an MRI uses magnets, it can attract metals. Before the scan, you will be asked to remove all jewelry and piercings and change into a hospital gown. Be sure to tell your doctor if you have any metal that was implanted in you from previous surgeries. Alert your doctor if any of the following items are present in your body:
- artificial heart valves
- prosthetic joints or limbs
If contrast dye will be used, tell your doctor about any allergies you have or allergic reactions you’ve had in the past.
If you’re claustrophobic, you may feel uncomfortable while in the MRI machine. Bring this up with your doctor so they can prescribe antianxiety medications to help with your discomfort. In some cases, you can also be sedated during the process. It might not be safe to drive afterward if you’ve been sedated. In that case, be sure to arrange for a ride home after the procedure.
An MRI machine looks like a large metal-and-plastic doughnut with a bench that slowly glides you into the center of the opening. So long as you’ve followed your doctor’s instructions and removed all metal, you’ll be completely safe in and around the machine. The entire process can take from 30 to 90 minutes.
If contrast dye is being used, a nurse or doctor will inject it through a tube inserted into one of your veins. In some cases, you may need to wait up to an hour for the dye to work its way through your bloodstream and into your spine.
The technician will have you lie on the bench, either on your back, side, or stomach. You may receive a pillow or blanket if you have trouble lying on the bench. The technician will control the movement of the bench from another room. They’ll be able to communicate with you through a speaker in the machine.
The machine will make some loud humming and thumping noises as the images are being taken. Many hospitals offer earplugs, while others have televisions or headphones for music to help you pass the time.
As the images are being taken, the technician will ask you to hold your breath for a few seconds. You won’t feel anything during the test.
After the test, you’re free to go about your day. However, if you took sedatives before the procedure, you shouldn’t drive.
If your MRI images were projected onto film, it might take a few hours for the film to develop. It will also take some time for your doctor to review the images and interpret the results. More modern machines display images on a computer, so your doctor can view them quickly.
It can take up to a week or more to receive all results from your MRI. When the results are available, your doctor will call you to review them and discuss the next steps in your treatment.