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Computed Tomography Education And Study Guide

Clicks:Updated:2013-03-26 23:03:30

Here are computed tomography education. Let’s learning about Computed tomography study guide.

Computed tomography is a  medical imaging method employing tomography created by computer processing. The word “tomography “is derived from the Greek tomos(slice ) and graphein.


A CT scanner is a special kind of X-ray machine. Instead of sending out a single X-ray through your body as with ordinary X-rays, several beams are sent simultaneously from different angles. The X-rays from the beams are detected after they have passed through the body and their strength is measured. Beams that have passed through less dense tissue such as the lungs will be stronger, whereas beams that have passed through denser tissue such as as bone will be weaker. A computer can use this information to work out the relative density of the tissue examined. Each set of measurements made by the scanner is, in effect, a cross-section through the body. The computer processes the results, displaying then as a two-dimensional picture shown on a monitor.


The introduction of helical or spiral CT represents the most important step in the evolution of CT scanning technology in recent years. In older CT scanners, the X-rays source would move in a circular fashion to acquire a single “slice”. Once the slice had been completed, the scanner table would move to position the patient for the next slice; meanwhile the X-rays source/detectors would reverse direction to avoid tangling their cables. In helical CT the X-rays source are attached to a freely rotating gantry. During a scan, the table moves the patient smoothly through the scanner. The mane of helical CT derives from the helical path traced out by the X-ray beam. It was the development of slip ring technology that made helical CT practical. In the mid 1980’s,an innovation called the power slip ring was developed so that the X-ray cable could be abandoned. The slip ring allows electric power to be transferred from a stationary power source onto the continuously rotating gantry. CT scanners with slop rings can rotate continuously and do not have to slow down to start and stop.


The major advantage of helical scanning compared to the traditional CT, is speed; a large volume can be covered in 20~60 seconds. The scanning time is dramatically shortened. The patient can often hole their breath for the entire study, reducing motion artifacts. The data obtained and the increased resolution. These mew 3-D reconstruction techniques a number of noninvasive “virtual endoscopy “ procedures to be performed. These major advantages led to the rapid rise of helical CT as the most popular type of CT technology.


Although there are many different types of CT scanners , the basic parts of the equipment are the same and consist of a scanning gantry, a computer and a display console. The scanner consists of a moveable X-ray table and the scanner gantry. A X-ray source and  an array of detectors, mounted within the gantry , rotate around the patient during each scan. The beam of X-ray is collimated before and after passing through the body. The detector records the attenuation values of the X-ray beam emerging form the patient.


Since its introduction in the 1970s, CT has become an important tool in medical imaging to supplement X-rays and medical ultrasonography. It has recently been used for preventive medicine or screening for disease, for example CT colonography for patients with a high risk of coloncancer, or full-motion heart scans for patients with high risk of heart disease.Usage of CT has increased dramatically over the last tow decades. An estimated 72 million scans were performed in the United States in 2007. Not only very common in medicine, CT is also used in other fields, such as nondestructive materials testing.

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