CT scanners are comprised of a number of integrated and interdependent CT parts, using a special computer and rotating x-ray device to create detailed, cross-sectional images, known as slices, of limbs, organ and other body parts.
The CT scanner system looks like a large, square doughnut. A flat patient couch, a distinctive CT part, is located in the circular opening which is 60 cm to 70 cm (24″ to 28″) in diameter. The patient lies on the adjustable couch, which can be moved up, down, forward, and backward to position the patient for imaging.
The CT scanner is a circular, rotating frame with an x-ray tube CT part mounted on one side and a banana-shaped detector CT part mounted on the other. A fan-shaped beam of x-rays is formed, as the rotating frame spins the x-ray tube detector CT part around the patient. For each complete rotation, one cross-sectional slice of the body is acquired. As the CT scanner rotates, the detector CT part takes numerous snapshots known as profiles. On average, about 1,000 profiles are taken in one rotation. Each profile is analyzed by the computer CT part, and the full set of profiles from each rotation is combined to form the slice which is a 2-dimensional image. This slice is focused to a thickness between 1 mm and 10 mm using lead shutters in front of the x-ray tube CT part and x-ray detector CT part.
Multiple computers (part of the CT part system) are used to control the entire CT organization. The main computer that coordinates the operation of the entire system is called the host computer. There is also a dedicated computer CT part that reconstructs the raw CT data into an image. A workstation with a mouse, keyboard and other associated controls allows the technologist to direct and monitor the exam. The gantry (framework) CT part and patient table CT part have multiple microprocessors that control the rotation of the gantry, movement of the table (up and down and in and out), tilting of the gantry for angled images, and other functions, such as turning the x-ray beam on and off.
The most modern and state-of-the-art CT scanners have 64-channels, increasing the number of snapshots or images obtained with each cycling of the CT part detector. This has finally enabled the CT scanner to capture diagnostic quality images of the coronary arteries and other vessels, which was not possible until very recently. Keep in mind though, that a mid-range 16-slice system can adequately perform most routine clinical exams.