Understanding a CT scan
April 07th, 2017
When a doctor is diagnosing a sinus problem, one of the most powerful tools available is a CT scan.
A CT scan takes images of an area of the body at different cross-sections. It’s also known as a CAT scan; the two terms refer to the same procedure. “CT” stands for “computed tomography,” which means that the machine takes many X-rays of the same body part at different depths. The doctor ends up with a thorough 3-D picture of the body part being assessed.
To visualize it, picture an apple. You don’t yet know what the inside of the apple looks like. But if you slice the apple into very thin slices (or cross-sections), and arrange them in order, you can look at the different “depths” of the apple and see how the structures extend inside the fruit in three dimensions. If there’s a bruise on the surface, for example, you can see how deep it goes; you can look at the cross-section from the very center, perhaps, and see how wide the structure is at the core of the apple.
CT scanners do this without any slicing. Instead, these machines use X-rays to look beneath the surface of the skin. They take a series of pictures that, when taken together, give a three-dimensional idea of what’s going on inside the body part being scanned.
Sinus CT scanning
CT scanning is used to picture abnormalities within the sinus cavities. ENT specialists use them regularly to help diagnose and treat patients with chronic sinus problems, and to determine whether surgery is warranted and how it should be done.
Sinus CT scanning is used for the following purposes:
- to assess fluid-filled or thick-membraned sinuses.
- to help confirm a sinusitis diagnosis.
- to assess disorders that cause inflammation.
- to learn about growths in the nasal cavity and sinuses (benign and cancerous).
- to create a “map” of the patient’s sinus cavities in order to plan for surgery.
In the CT scan images below, you can see the different sinuses. The black areas indicate that there is air in that area of the image. White areas indicate bone or fat. Gray indicates tissue or water. In your sinuses, which are air-filled cavities, normal, healthy sinuses should be predominantly black.
Figure Legend: Ethmoid sinus (white arrow). Maxillary sinus (asterisk)