What does the CT equipment look like?

The CT scanner is typically a large machine with a hole, or short tunnel, in the center. A moveable examination table slides into and out of this tunnel. In the center of the machine, the x-ray tube and electronic x-ray detectors are located opposite each other on a ring, called a gantry, which rotates around the patient. The computer that processes the imaging information and monitor are located in a separate room where the CT technologist sits. The technologist will always be able to see your child in the CT scanner.

How does the procedure work?

In many ways, CT scanning is like other x-ray examinations. X-rays are a form of radiation, like light or radio waves that can be directed at the body. Different body parts absorb the x-rays in varying degrees.

In a conventional x-ray exam, a small burst of radiation passes through the body, recording an image on photographic film or a special image recording plate. Bones appear white on the x-ray; soft tissues show up in shades of gray and air appears black.

With CT scanning, numerous x-ray beams and a set of electronic x-ray detectors rotate around the patient. At the same time, the examination table is moving through the scanner, so that the x-ray beam follows a spiral path. A special computer program processes this series of pictures, or slices of the body, to create two-dimensional cross-sectional images, which are then displayed on a monitor. Special software can also generate three-dimensional (3-D) images when requested by your physician or the radiologist interpreting the exam.

CT imaging is sometimes compared to looking into a loaf of bread by cutting the loaf into thin slices. When the image slices are reassembled by computer software, the result is a very detailed multidimensional view of the body's interior.

Refinements in detector technology allow new CT scanners to obtain multiple slices in a single rotation. These scanners, called "multislice CT" or "multidetector CT," allow thinner slices to be obtained, resulting in more detail of the body, in a shorter period of time.

Modern CT scanners are so fast that they can scan through large sections of the body in just a few seconds. Such speed is beneficial for all patients but especially children, the elderly and critically ill.

For some CT exams, a contrast material is used to enhance visibility in the area of the body being studied.