CT Scan (Computed Tomography) and CAT Scan (Computed Axial Tomography)

CT ScanComputed Tomography (CT) imaging is also known as Computed Axial Tomography (CAT), imaging. Often, it is simply called a CT or CAT scan. It is a type of diagnostic imaging that uses low-intensity x-rays to create multiple, detailed pictures of the inside of your body, such as your cervical (neck) or lumbar (low back) spine.

Computed tomography is an important diagnostic tool in spine medicine. It renders images in greater detail distinguishing bone from soft tissues and vascular structures. Many different spine professionals, including neurosurgeons and orthopaedic spine surgeons, rely on CT scans to confirm a patient's diagnosis.

CT scans are performed in a hospital or radiology facility. After your test, the radiologist evaluates the results and prepares a written report, which is sent to the ordering physician.

When your physician may order CT Scan imaging:

  • After trauma to the spine (CT is often faster than MRI)
  • Before spine surgery*
  • To confirm the diagnosis of a spinal disorder (eg, herniated disc, tumor, fracture)
  • When myelography is necessary
  • Measure bone loss or bone mineral density (eg, test for osteoporosis)

*CT images can be saved as digital files (eg, computer, flash drive) and used for planning a patient's spine surgery.

What to tell your ordering physician and radiologist:

  • If you are or could be pregnant or if you are breastfeeding. If you are breastfeeding, you may be asked to stop for two days.
  • Are claustrophic; a mild sedative may be administered.*
  • If you are allergic to contrast medium or had a previous reaction to IV dye.
  • If you are allergic to latex.

*If you require a mild sedative, you need to have someone drive you home.

CT Scan with Contrast Medium
Your physician's orders to the radiologist may include the test be performed with contrast—a material that is injected through an intravenous line (IV) placed in your hand or arm. Contrast can help to highlight image detail. When the test is ordered with contrast, the test is performed in two steps.

  • Step 1: Without the contrast medium
  • Step 2: After the contrast medium is injected, the next set of images are obtained.

How a CAT Scan is Performed
After arriving at the testing facility, you are asked to change into a gown and remove any metal (eg, coins) and jewelry. Your clothes are stowed in a secure locker.

The radiologist or radiology technician positions you lying on your back on the CT scanner bed and may place a triangular cushion under your knees. Next, the table is slid into the scanner.

Throughout the test, the radiologist can see you through a large window, and can hear you speak. At certain times during the test the radiologist will ask you to hold very still or hold your breath for several seconds. You will hear the scanner rotating and the table may be adjusted by the radiologist during the procedure.

If your CAT scan is ordered with contrast, the contrast is injected through the IV line in your hand or arm. You may feel a slight warming sensation as the contrast is injected and spreads throughout your body. Next, the final images are obtained and the IV is removed.

After Your Test
You change back into your street clothes and are discharged home. If your test included contrast, you may be instructed to drink plenty of fluid (eg, water, juice) the next 24-hours to flush the contrast out of your system.


Radiological Society of North America, Inc. (RSNA). Computed Tomograph (CT)—Spine. March 7, 2013. http://www.radiologyinfo.org/en/info.cfm?pg=spinect. Accessed February 12, 2015.

Updated on: 12/15/15
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