Magnetic resonance imaging is a noninvasive diagnostic tool that uses radio waves and a magnetic field to produce detailed images of the inside of a body. Doctors can use them to examine a person’s lower spine, or lumbar region, and the surrounding tissues.
The exam itself is very safe because it does not use ionizing radiation, which can kill or damage cells, and the person cannot feel the magnetic field or the radio waves.
In this article, we discuss what doctors use magnetic resonance imaging (MRI) for, how to prepare for an MRI, and what happens during an MRI. We also cover the risks of an MRI and when a person can expect to get the results of the scan.
Medical professionals perform lumbar MRIs for a variety of reasons. If someone is experiencing pain in their lower back, a doctor may recommend a lumbar MRI scan to help diagnose the source of the pain.
A doctor may also order a lumbar MRI for a person who is about to undergo back surgery. In this case, the surgical team uses the results of the lumbar MRI to help plan the operation.
A lumbar MRI is a powerful diagnostic tool that doctors may use to:
- check spinal alignments
- detect abnormalities of vertebrae or the spinal cord
- evaluate any inflammation of the spinal cord or nerves
- check for tumors on or around the spinal cord
- monitor damage to the spine after an injury
- monitor the spine after an operation
- explore different causes of back pain
A doctor may order a lumbar MRI if a person has any of the following symptoms:
- sudden back pain that occurs alongside fever
- injury or trauma to the lower spine
- severe and persistent lower back pain
- multiple sclerosis
- leg pain that suggests a lumbar disc herniation
- bowel or bladder incontinence
Before going for an MRI, a person can usually eat, drink, and take their medication as normal, unless the doctor has specified otherwise. However, it is important for an individual to inform their doctor if they:
- have any metal implants, such as a pacemaker or a hip or knee replacement
- might be pregnant
- have a history of allergic reactions, which is important if the scan requires the use of a contrast dye
Metal objects can affect the safety and effectiveness of an MRI scan. Before the examination begins, the MRI technician will ask the person to remove any metal items they are wearing, such as:
- body piercings
For a lumbar MRI, the person will also need to remove their clothing and wear a hospital gown. The technician may also ask the person to fill out a medical questionnaire and sign a consent form.
Because an MRI involves lying down inside a windowless chamber for an extended period, people who experience claustrophobia may find the procedure uncomfortable or even frightening. If this is the case, the doctor may prescribe an anti-anxiety medication or sedative to help the person relax during the scan.
A lumbar MRI is a fairly short procedure, and the person is usually free to go home afterward. According to one MRI provider, the scanning phase of a lumbar scan takes around 20 to 35 minutes.
The MRI machine looks like a giant doughnut. An MRI technician will ask the individual to lie down on a table that slides into the opening of the machine. The technician will perform the MRI under the direction of a radiologist, who is a specialist in X-rays and radiation processes. They will maintain verbal contact with the person they are examining through a microphone.
Because the machine can be very loud, the technician will usually give the person earplugs or headphones to wear.
MRI technicians sometimes also use gadolinium, which is a type of contrast dye, to help enhance the quality of the images that the MRI scan produces. They inject the contrast dye through an intravenous line into a vein in either the hand or the arm of the person.
The MRI machine uses a strong magnetic field that aligns and stimulates particles called protons in the body, forcing them to spin out of alignment.
When the technician halts the magnetic field, the protons begin to spin in their usual way. As they do this, they give off energy that the MRI machine detects. The MRI machine records this information, and a computer processes the data to create a detailed image of the body area.
To produce high-quality images, the person must remain completely still during the entire scanning process.
Although doctors consider an MRI scan to be a very safe procedure, there a few safety concerns to keep in mind.
The strong magnetic field inside the machine will attract metal objects, such as jewelry. If these objects are too close to the scanner, the magnetic field may cause them to move at speed. This could damage the scanner or even injure the person undergoing the scan. This is why it is essential to remove any metal objects before the examination begins.
There are risks for people who have metal implants, such as pacemakers or surgically-implanted pins. Again, because the MRI machine emits a strong magnetic field, it can cause metal implants inside the body to move.
However, having a metal implant does not always prevent a person from having an MRI scan. Doctors will assess the risk on an individual basis.
Due to the strength of the magnetic field, the MRI machine may create a repetitive tapping or thumping noise. This may adversely affect a person’s hearing if they do not wear proper ear protection.
Side effects from MRI scans are rare, but they can happen. Some side effects from MRIs include:
- thermal injuries, such second-degree burns
- injuries from metal objects becoming projectiles
- hearing loss or tinnitus, which is a ringing in the ear
On rare occasions, people may experience side effects from the contrast dye, which can include:
- pain at the site of injection
- a headache
- itchy or irritated eyes
- hives, which is a bumpy and intensely itchy red rash
A person is usually free to go home after the MRI scan. If the person had a sedative to help them relax during the procedure, they might need someone to pick them up from the hospital or clinic.
After the examination, the radiologist will interpret the results and write a report, which they send to the person’s doctor. The doctor will then share the findings with the individual either in person or over the phone. The doctor will also add the MRI results to the person’s medical file.
People can expect their MRI results within a week after the examination.
A lumbar MRI is a noninvasive procedure that doctors use to help diagnose lower back pain, plan back surgery, or monitor progressive medical conditions, such as multiple sclerosis.
The scanning process itself lasts about 20 to 35 minutes. The procedure is entirely painless, and there are very few side effects or risks. Lumbar MRIs are outpatient procedures, so the person is usually free to leave the hospital or clinic after the examination.