Myelography involves imaging the spinal cord after injection of which substance?

• A. A contrast medium to identify distortions caused by tumors, cysts, herniated disks, or other lesions.
• B. A radioactive tracer.
• C. Air to expand tissues.
• D. A saline solution.

Answer: (A)

Imaging the spinal cord with myelography is done by injecting a contrast medium into the spinal canal to outline the thecal sac and nerve roots on radiographs or CT. This contrast highlights distortions caused by tumors, cysts, herniated disks, or other lesions, making them visible where the normal CSF space would appear. The contrast agent is radiopaque, allowing the clinician to assess compression and structural relationships. The other options don’t provide the necessary radiographic delineation: a radioactive tracer is used for different nuclear medicine studies, air was used in older pneumoencephalography, and a saline solution would not create the contrast needed to visualize the spinal structures.