What imaging exam uses a contrast medium injected into the spinal canal?

The correct answer, myelography, involves the injection of a contrast medium directly into the spinal canal to enhance the visibility of the spinal cord and nerve roots during imaging. This procedure is typically performed using fluoroscopy or X-ray guidance, allowing radiologists to assess conditions such as herniated discs, spinal stenosis, tumors, or any abnormalities affecting the spinal cord.

Myelography is particularly useful because the contrast medium creates a clearer image of the soft tissues surrounding the bones of the spine, which are often difficult to visualize using standard imaging techniques alone. By enhancing the contrast of the spinal structures, it allows for more accurate diagnoses and helps guide treatment options.

While other imaging modalities like CT scans or MRIs can also evaluate the spinal canal, they do not require the direct injection of a contrast medium into the spinal canal. CT scans typically use contrast for vascular studies or when specific soft tissue evaluation is needed, but this is different from the myelographic technique. Ultrasound does not generally provide adequate visualization of the bony structures or the spinal canal, making it unsuitable for such assessments. Thus, myelography stands out as the specific imaging exam that employs a contrast medium injected into the spinal canal.