MRI Scan Procedure
A thoracic (upper back) or lumbar (lower back) MRI (Magnetic Resonance Imaging) scan is used to create a detailed image of the back area. It is predominately used to identify soft tissue injuries, in contrast to a CT (Computed Tomography) scan, which is the preferred method for issues involving bones.
An MRI machine creates a strong magnetic field to align the molecules in the spine in a certain way. Radio waves are used to give energy to these molecules. When the magnetic field is turned off, the molecules return to their normal state, releasing the energy provided by the radio waves. This energy is read by the MRI machine and used to create images of the scanned area, called ‘slices’. One MRI examination creates many slices, which are combined to create a 3-dimensional reproduction of the scanned area. MRI scans, unlike CT scans, do not deliver X-rays or radiation and are therefore extremely non-intrusive.
Special dyes, known as ‘contrast agents’, are sometimes injected into the arm to improve the clarity of the final image. The most common type of ‘contrast’ used is gadolinium, which is very safe as it is non-toxic and allergic reactions to the substance are extremely rare.
During the examination, the patient lies on a narrow table, which slides into the tunnel-shaped MRI scanner, for 30 to 60 minutes. They will have to lie still, as too much movement can blur the MRI images and cause errors in the final reading. The whole process is pain free.
Reasons for Undergoing a Thoracic or Lumbar MRI Scan
The most common reasons for a thoracic or lumbar MRI scan are to identify the causes of severe back pain that has not been resolved by conservative treatment such as medication in conjunction with physical therapy, or when the back pain is accompanied with leg weakness or numbness – often an indication of a nerve condition.
A thoracic or lumbar MRI scan can also be used to identify a multitude of less common spinal conditions, including sclerosis, scoliosis, arthritis, infection of the spine, or after an injury or trauma to the spine. Furthermore, an MRI scan may also be conducted before or after spinal surgery as a guide for the operating surgeons.
Common conditions causing pain in the back that can be revealed by a thoracic or lumbar MRI scan include herniated or ‘slipped’ discs (cervical radiculopathy), narrowing of the cervical spine (spinal stenosis) or abnormal wear of the bones and cartilage in the back (cervical spondylosis).
Less common findings are usually any condition that can affect the soft tissues of the back. These include bone infections (osteomyelitis), disk inflammation (diskitis), infection of the spine, multiple sclerosis, spinal cord injuries or compression, spinal fractures or spinal tumours.
If the thoracic or lumbar spine, the area of the spine that runs through the lower or upper back respectively and nearby nerves, appears normal in the MRI results but the pain continues, other methods of investigation and diagnosis can be pursued. These include other scans such as CT scans or X-rays, or further investigation into conditions such as Fibromyalgia.