How CT Scans Work

A CT (computed tomography) scan or "cat scan" as they used to be called, is one of several diagnostic procedures that helps give doctors a better idea of what is going on inside a patient's body. Unlike X-rays, which only take one image of the body, CT scans take a series of images. Each image is a cross section of a portion of the body. When all the cross sections are put together with the help of the computer, they provide a much more in-depth look.

The advantage to having a CT scan done rather than an X-ray, is that a CT can "see" more features that would not be visible on a standard X-ray. For example, organs and tissues show up more readily on a CT scan. Additionally, a CT scan exposes the patient to less radiation than an X-ray, thereby making it a safer procedure. This is especially important since many cystic fibrosis patients will undergo dozens of X-rays in the course of a lifetime of treatment.

But how does it work?

The CT scanner device looks like a large doughnut that can rotate and tilt. X-ray beams on one side of the center opening are aimed directly across to a detector on the opposite side. The X-ray tube is positioned 180 degrees from the detector, similar to how a pitcher and catcher are positioned in baseball. The beams, like the baseball, are thrown from the x-ray tube (pitcher) to the detector (catcher.) This all happens at a very rapid pace. Moreover, the x-ray tube and detector maintain their relative positions to one another, all while continually rotating around the circle of the scanner.

The patient lies on a narrow table that is slowly moved through the center of the scanner. For the most part, the procedure is not altogether uncomfortable or confining. In some cases, such as scans of the sinuses or brain, the patient's head is stabilized or strapped down. This prevents the patient from moving while the scanner generates a 360 degree cross section.