What are the indications, advantages, and disadvantages of radiography, computed tomography (CT), and magnetic resonance imaging (MRI) in the evaluation of the spine?
Radiography of the spine may be obtained to assess for vertebral alignment, fractures including compression deformities, and degenerative changes and as part of the workup for back pain. It may also be obtained to assess spinal alignment and hardware appearance after spinal fusion surgery. However, radiographs do not show details of the soft tissue structures such as the intervertebral discs, ligaments, spinal cord, and nerves.
CT of the spine is most commonly used in the setting of acute trauma to assess for fractures. However, when contraindications to MRI are present, CT may be used instead to evaluate for suspected tumor, infection, and spinal cord pathology. Intervertebral discs, spinal canal, and neural foramina are still evaluable on CT, although their visualization is inferior when compared to that on MRI. CT is more sensitive than MRI for detecting calcification, gas, and certain osseous pathologies such as spondylolysis. However, streak artifacts from metallic hardware may obscure portions of the spine in patients who have had prior surgery, leading to limited evaluation.
MRI of the spine may be obtained to assess for suspected tumor, infection, and spinal cord pathology (all beyond the scope of this chapter). MRI is the modality of choice for assessment of spinal degenerative disease and associated effects upon the spinal canal, neural foramina, ligaments, spinal cord, and nerve roots. It is also useful for evaluation of the surrounding musculature. However, susceptibility artifacts from metallic hardware may obscure portions of the spine in patients who have had prior surgery, also leading to limited evaluation.