What is computed tomography? - Pamphlet

Conventional X ray Images

All x-ray imaging is base on the absorption of x rays as they intervene through the different parts of a patient's body. Depending on the amount obsessed in a unique tissue such as muscle or lung, a different amount of x rays will pass through and exit the body. The amount of x rays spellbound contributes to the radiation dose to the patient. During conventional x-ray imaging, the exiting x rays interact beside a detection device (x-ray film or other picture receptor) and provide a 2-dimensional projection image of the tissues inside the patient's body--an x-ray produced "photograph" call a "radiograph." The chest x ray (Figure 1) is the most adjectives medical imaging examination. During this nouns, an image of the heart, lungs, and other anatomy is record on the film.

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Computed Tomography (CT)

Although also base on the variable incorporation of x rays by different tissues, computed tomography (CT) imaging, also known as "CAT scan" Computerized Axial Tomography), provides a different form of imaging known as cross-sectional imaging. The kernel of the word "tomography" is from the Greek word "tomos" meaning "slice" or "fragment" and "graphe" meaning "drawing." A CT imaging system produces cross-sectional descriptions or "slices" of anatomy, like the slices surrounded by a loaf of bread. The cross-sectional images (Figure 2) are used for a range of diagnostic and therapeutic purposes.

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How a CT system works

1. A motorized table moves the forgiving (Figure 3) through a circular opening contained by the CT imaging system.

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2. As the patient pass through the CT imaging system, a source of x rays rotates around the inside of the circular opening. A single rotation take about 1 second. The x-ray source produces a shrink, fan-shaped beam of x rays used to irradiate a slot of the patient's body (Figure 4). The concreteness of the fan lintel may be as small as 1 millimeter or as large as 10 millimeters. In typical examinations in that are several phases; each made up of 10 to 50 rotations of the x-ray tube around the forgiving in coordination beside the table moving through the circular opening. The long-suffering may receive an injection of a "contrast material" to facilitate visualization of vascular structure.

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3. Detectors on the exit side of the forgiving record the x rays exiting the slice of the patient's body person irradiated as an x-ray "snapshot" at one position (angle) of the source of x rays. Many different "snapshots" (angles) are collected during one complete rotation.

4. The data are sent to a computer to recreate all of the individual "snapshots" into a cross-sectional picture (slice) of the internal organs and tissues for each complete rotation of the source of x rays.

Advances contained by Technology and Clinical Practice

Today most CT systems are capable of "spiral" (also call "helical") scanning as ably as scanning surrounded by the formerly more conventional "axial" mode. In addition, several CT systems are capable of imaging multiple slices simultaneously. Such advance allow relatively larger volumes of anatomy to be imaged in relatively smaller quantity time. Another development contained by the technology is electron beam CT, also specified as EBCT. Although the principle of creating cross-sectional images is impossible to tell apart as for conventional CT, whether single- or multi-slice, the EBCT scanner does not require any moving parts to generate the individual "snapshots." As a result, the EBCT scanner allows a quicker image attainment than conventional CT scanners.