MRI 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 these images to examine a person’s lower spine, or lumbar region, and the surrounding tissues.
The technology is safe because it does not use ionizing radiation, which can kill or damage cells, and a person cannot feel the magnetic field or the radio waves. However, there may be some things to consider before going ahead.
In this article, we discuss how doctors use a lumbar MRI to examine an individual’s lower back, how to prepare, and what happens during an MRI. We also cover the risks of an MRI and when a person can expect to get the results.
According to the American Academy of Family Physicians (AAFP), low back pain is one of the most common reasons for outpatient visits to hospitals, clinics, or other healthcare facilities.
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.
The main reasons a doctor will recommend an MRI is to investigate:
- Lower back pain: This can result from muscle strain, joint damage, or other reasons.
- Sciatica: This causes acute pain and results from irritation to a nerve root, possibly due to inflammation or structural changes.
- Claudication: This can lead to mobility problems and dull pain or aching in the lower limbs. Claudication can be vascular, affecting the blood vessels, or neurogenic, involving the nerves.
A doctor may also order a lumbar MRI for an individual 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 alignment
- detect abnormalities of vertebrae or the spinal cord
- check for a lumbar disk herniation, which can lead to leg pain
- 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 will not usually carry out a lumbar MRI during the first 6 weeks that a person experiences pain unless the person has:
- sudden back pain that occurs alongside fever
- injury or trauma
- sudden back pain with spinal tenderness, possibly linked to cancer, osteoporosis, or steroid use
- bowel or bladder incontinence
- a serious underlying condition, such as cancer
The reason for delaying a lumbar MRI is that most cases of back pain resolve within a few weeks, according to the AAFP. A herniated disk will usually reabsorb within 8 weeks. Carrying out a lumbar MRI too early could lead to unnecessary cost and anxiety.
A lumbar MRI can indicate the reason a person is experiencing back, leg, or other type of pain.
It can show signs of:
- a congenital or developmental variant, a feature that a person has developed or had since birth
- degenerative changes, such as a herniated disk or disk that has broken down, called an annular fissure
- inflammation or infection
- a benign or malignant tumor
- central vertebral canal stenosis, in which a narrowing occurs that leads to nerve compression in the spine
- ankylosing spondylitis, which may involve inflammation and changes in the shape of the spine
- spondylolisthesis, where a vertebra slips out of place, affecting spinal alignment
- other changes, such as an abscess
If the image is normal, there is no need for action.
It is of note that no diagnostic technology is fully reliable, although some studies have suggested up to 100% success rates for a lumbar MRI detecting a herniated disk.
An MRI will not definitely show that a person has a specific problem, and the person may need further tests. In addition, there is a possibility of a false-positive result, where a scan suggests that a problem is present when it is not.
An MRI scan usually takes 15–90 minutes. This will depend on where a person has the scan and which images they are taking.
An individual is usually free to go home after the MRI scan and continue with their daily routine.
If they have 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, a radiologist will interpret the results and write a report to send to the person’s doctor. The doctor will then share the findings with the individual. They will also add the MRI results to the person’s medical file.
People can expect their MRI results within 1 week after the examination, although this may vary.
Before going for an MRI, a person can usually eat, drink, and take their medication as usual, unless a doctor has specified otherwise. However, it is important for an individual to inform the 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.
An MRI involves lying down inside a windowless chamber for an extended period, and therefore people who experience claustrophobia may find the procedure uncomfortable or even frightening. If this is the case, the doctor may prescribe an antianxiety medication or sedative to help the person relax during the scan.
The MRI machine looks like a giant doughnut. A radiologist or MRI technician will ask an individual to lie down on a table that slides into the opening of the machine.
If a technician performs the MRI, they will do so 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.
Sometimes, MRI technicians also use gadolinium, which is a contrast dye, to gain a clearer image.
They will inject the contrast dye before the scan through an intravenous line into a vein in either the hand or the arm of the person.
How an MRI works during a scan
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.
Other things to expect are the following:
- To produce high quality images, it is essential for a person to stay still during the scan. A radiologist or technician will ensure the person is as comfortable as possible before starting.
- The machine can be very loud, and the radiologist or technician will usually give the individual earplugs or headphones to wear.
- A two-way communication system will allow the person to speak with the radiologist or technician at intervals during the scan.
Although doctors consider an MRI scan to be a very safe procedure, there are some 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.
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
- thermal injuries, such as second degree burns
- injuries from metal objects becoming projectiles
- hearing loss or tinnitus
On rare occasions, people may experience side effects from the contrast dye, such as:
- pain at the site of injection
- a headache
- itchy or irritated eyes
- hives, which is a bumpy and intensely itchy rash
According to the American College of Radiology, a contrast dye is unlikely to cause harm to a breastfed infant. Anyone who has concerns should seek guidance from a doctor.
The cost of a lumbar MRI can vary widely, depending on various factors, such as:
- where the treatment takes place
- the extent of the area that needs scanning
- whether the scan involves a contrast dye
- whether a person needs sedation to help them stay still
In some cases, insurance may cover all or part of the cost.
Learn how Medicare can help with the cost of an MRI scan here.
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 procedure is 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.