A magnetic resonance imaging (MRI) test 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 tissues of the body, like muscles, along with your bones.
An MRI can be performed on any part of your body. However, a lumbar MRI specifically examines the lumbar section of your spine—an area where back problems commonly originate.
The lumbar spine is made up of five vertebral bones, the sacrum (the bony “shield” at the bottom of your spine), and the coccyx (tailbone). In addition to bones, the lumbar spine is comprised of large blood vessels, nerves, tendons, ligaments, and cartilage.
Your doctor will use an MRI scan 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 scan if you have the following symptoms:
- back pain accompanied by fever
- birth defects affecting the spine
- injury to the lower spine
- lower back pain
- multiple sclerosis
- problems with your bladder
- signs of cancer
- weakness, numbness, or other problems with your legs
Your doctor might also perform a lumbar MRI if you are scheduled for spinal surgery, so that he or she can plan the procedure before making an incision.
An MRI provides a different kind of image than other imaging tests—such as X-rays, ultrasound, or computed tomography (CT) scans. 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 X-rays and computed tomography (CT) scans, an MRI does not use radiation. It is considered a safer alternative for everyone, especially pregnant women. Although side effects do sometimes occur, they are 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 cause problems with pacemakers or cause implanted screws or pins to shift in the body.
One complication that can also arise is an allergic reaction to the contrast dye. The most common type of contrast dye is gadolinium. However, these allergic reactions are often mild and easily controlled by medication.
If you are claustrophobic, you may feel uncomfortable while in the MRI machine. However, there is nothing to fear. Your doctor may prescribe antianxiety medication to help with your discomfort. In some cases, you can also be sedated during the process.
Before the test, tell your doctor if you have a pacemaker. Depending on your 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 are not disrupted during the examination.
Since the MRI uses magnets, it can attract metals. 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
Some MRI examinations use contrast dye that is injected into the bloodstream. This helps provide a clearer image of the blood vessels in that area. The dye—typically gadolinium—can sometimes cause an allergic reaction. Tell your doctor about any allergies you may have or if you’ve had an allergic reaction in the past.
Before the scan, you will be asked to remove all jewelry and change into a hospital gown.
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 have followed your doctor’s instructions and removed all metal, you will be completely safe in and around the machine.
If contrast dye is being used, a nurse or doctor will inject it through an intravenous (IV) line. 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 using a remote control from another room. He or she will be able communicate with you over a microphone.
The machine will make some loud whirring and thumping noises as the images are being taken. Many hospitals offer earplugs, while others have televisions or headphones to help you pass the time.
As the pictures are being taken, the technician will ask you to hold your breath for a few seconds. You won’t feel anything during the test as the magnets and radio frequencies—those similar to FM radios—cannot be felt.
The entire process can take from 30 to 90 minutes.
After the test, you are free to go about your day. If you took sedatives before the procedure, you should not drive. Instead, arrange for a ride home after the test.
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.
The initial results from an MRI scan may come within a few days, but your comprehensive results can take up to a week or more. When the results are available, your doctor will call you in to review them and discuss the next steps for your treatment.