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Medical Imaging

CT (CAT) Scan

The CT Scanner uses X-rays to produce an image. When you have an X-ray of your hand, the radiation moves through your hand and onto a film to produce an image. CT Scanners work much the same way, except instead of film, detectors capture the radiation after it passes through your body.

The patient moves through the gantry (circular donut shaped part of the scanner) on a movable table. At the same time, a rotating X-ray machine inside the gantry moves around the body. As the patient moves through the gantry, the detectors constantly collect data as the radiation passes through your body, and with the aid of a complex computer, a two -dimensional image is created.

A completed scan may have as little as 20 images, such as CT of the brain, while others have several hundred images, as is the case with a CT of the abdomen. Each image represents a section of the body, which can be thick (10mm) or thin (0.5mm) depending upon the body part being examined. The CT examination is fast and painless.

The CT scanners at St. Michael's Hospital are state of the art spiral CT and multislice scanners. Images can be viewed individually or in rapid sequence called cini view, or reconstructed by the technologist as a three - dimensional model which can be manipulated and rotated to provide the physician with an optimal image for review.

Multislice CT scanners operate with greater speed, allowing advanced CT angiography scanning. The increase in speed is an advantage for all patients as the scan time is decreased considerably, but is most beneficial to elderly and critically ill patients who are not able to sustain long breath holds.