Computed Tomography (CT) Scan
CAT scan pictured
What is it?
The CT or “CAT” scan is an X-ray test that shows bones and soft tissues. The abbreviation “CAT” stands for Computer Assisted Tomography. X-rays are taken and then interpreted by a powerful computer that makes them appear as “slices” through the body. Special software can combine these images into a three-dimensional view of the bones.
Why is it done?
The “slices” produced by a CT scan allow each section of the spine to be examined separately. The images show details of the bones that comprise the spine in great detail. A CT scan can show whether bone spurs are pushing against spinal nerve roots . It is often used when looking at spinal fractures or bones that have been damaged by infection or cancer. Some doctors have recently begun using CT scan technology on a limited basis to test for osteoporosis in the spine.
How is it done?
A CT scan is similar to having an MRI test. You will be asked to lie on a table that slides into a scanner. The scanner used for CT scans is essentially an X-ray tube that rotates in a circle. You will need to lie very still while the scanner takes many pictures. The procedure takes 30-60 minutes.
What are the limitations?
The CT scan does not show muscles or ligaments clearly. To make the nerves and soft tissues easier to see, this test is often combined with a myelogram.
What are the risks?
The CT scan uses X-rays. In large doses, radiation from the X-rays can increase the risk of cancer. The vast majority of patients who have a CT scan will never get enough radiation to worry about it causing cancer. Only patients who must have large numbers of X-rays or CT scans – hundreds over many years – need to be concerned. Children, and young adults who plan to have children, should be protected from radiation exposure to the testicles and ovaries because the radiation may damage the sperm and eggs. The person performing the CT scan will usually protect these areas for you by shielding them with a lead apron or lead blanket.
A Patient’s Guide to CAT Scans
What it is: The CAT scan is an X-ray test that is similar to both the MRI and a regular X-ray, because it can show both bones and soft tissues. The CAT scan uses X-rays that are interpreted by a powerful computer to create images that appear as “slices” through the body. Today, using the computer software, these slices can be combined by the computer to actually give a 3-D view of the bones of the spine.
What the test shows: CAT scans are also able to produce X-ray “slices” taken of the spine, so each section of the spine can be examined separately. The CAT scan was developed before the MRI, and for several years, was used to show the soft tissues of the spine. The pictures of the soft tissues produced by a CAT scan are probably not as clear as the MRI. To make the soft tissues easier to see, the CAT scan is often combined with a myelogram. For the myelogram, dye is placed into the spinal sac to outline the nerves and spinal sac so they show up clearly on the X-ray. Because the CAT scan uses X-rays, it shows the bones of the body in great detail. It is the test of choice when looking at fractures or damaged bones due to infection or cancer.
What the test does not show: A CAT scan without dye is not as good at showing the discs and the nerves of the spine. The MRI is the best test to show problems such as a herniated disc. The CAT scan does not show muscles or ligaments clearly.
How the test is done: As with an MRI, a CAT scan will require you to lie on a table that slides into a scanner. The scanner is essentially an X-ray tube that rotates in a circle taking many pictures. The procedure takes 30-60 minutes. You will have to lie very still for short periods as the scanner is taking the pictures.
What risks the test has: The CAT scan uses X-rays (which use radiation). In large doses, this can increase the risks of cancer. The vast majority of patients who have a CAT scan will never get enough radiation to worry about cancer. Only patients who must have multiple X-rays and CAT scans (hundreds) over many years need worry about this risk. Children and young adults who plan to have children should be protected from radiation exposure to the testicles and ovaries. The radiation may damage the sperm and eggs. It is simple to protect the area whenever possible by shielding it with a lead apron or blanket.
What the test costs: A CAT scan of the spine usually has two costs associated with the test. The first cost is the fee for actually doing the test. This is called the “technical fee”. The second cost is the fee of having a specialist, such as a radiologist, read and interpret the test. This is called the “professional fee”. You may get two bills for this test: one from the hospital or clinic where you and the CAT scan done, and one from the specialist who read the test.