Is CT the same as X-ray (please don't disturb non-professionals)

X-rays, also known as roentgen rays, are generally used to see through the body in medicine, and can only produce black and white images, which are generally used to see through the front or back of the body. Generally, X-rays still do some harm to the body, but once or twice they won't do much harm to the body, and more will not do.

CT is the abbreviation of Computerized X-ray Tomography or Computerized X-ray Tomography. This is the biggest breakthrough in X-ray diagnosis since Roentgen discovered X-rays in 1895. It is a combination of computer control technology and X-ray detection photography technology. CT was successfully developed by British physicists in 1972. It was first used for the diagnosis of brain diseases, and then extended to general examination in 1976. This is a great revolution of X-ray in radiology. China also introduced this new technology in the late 1970s. In a short period of 30 years, thousands of various types of CT machines have been installed in hospitals all over the country and even in counties and townships, and CT examination has quickly spread all over the country, becoming an indispensable equipment for medical diagnosis.

CT is developed from X-ray machine, which significantly improves the resolution of X-ray examination, and its resolution and qualitative diagnosis accuracy are much higher than those of general X-ray machine, thus broadening the application scope of X-ray examination and greatly improving the accuracy of X-ray diagnosis.

CT scans a certain part of the human body with an X-ray beam according to a certain thickness. When X-rays are aimed at human tissues, part of the rays are absorbed by the tissues, and part of the rays pass through the detected organs of the human body to generate signals. Because the density of various tissues in the human body is different, the X-ray penetration ability is different, and the rays received by the detector are also different. The received differential ray signal is converted into digital information, then processed by a computer and output to a display screen to display an image, which is called a sectional image. CT is characterized by simple operation, no pain to patients, high density and high resolution. It can observe very tiny lesions in human body and directly display organs and lesions that X-ray films can't. It is very sensitive and reliable in finding lesions and determining their relative spatial position, size and number, which has special value, but it has certain limitations in the diagnosis of pathological properties of diseases.

CT is different from traditional X-ray photography. The X-ray detection system used in CT is more sensitive than photographic film, and the data obtained by the detector is processed by computer. The characteristic of CT is that it can distinguish X-ray absorption values with little difference. Compared with the traditional X-ray photography, CT can distinguish the density range of more than 2000 levels, while the traditional X-ray film can only distinguish the density of about 20 levels. This density resolution can not only distinguish fat from other soft tissues, but also distinguish the density grade of soft tissues. This revolutionary technology has greatly changed the diagnosis of many diseases.

Horizontal section is the most commonly used fault plane in CT examination, and inspectors can determine the thickness and position of the fault plane. The commonly used slice thickness is between1~10 mm. After the moving patient passes through the examination box, several connected images can be obtained, which can be combined into a body structure. Using thinner slices can get more accurate data, but at this time, more slices must be scanned for a certain volume of structure.

The data obtained by each exposure is reconstructed by computer to form images, which can be displayed on the screen or photographed for permanent storage. In addition, its basic data can also be stored on magneto-optical disks or magnetic tapes.