1 CT is inseparable from the German physicist Roentgen.
Speaking of CT, there is one person who can't pass. This man is the German physicist wilhelm rontgen (1845-1923). Without his discovery of X-rays, there would be no invention of CT, which was invented on the basis of X-rays.
18951October 8th, 165438+ roentgen discovered x-rays,1February 22nd, 895, and took the first medical x-ray film in human history. X-ray diagnosis technology has become the earliest non-invasive examination technology in the world, so Roentgen is honored as "the father of diagnostic radiology".
Because the density of human tissues is different, the absorption rate of X-rays is also different. In this way, when X-rays pass through human tissues, there will be different degrees of attenuation, and the exposure on the film will be different, which will lead to changes in gray scale and thus form an image. According to this image, we can diagnose which part is diseased.
In order to permanently commemorate this great scientist who promoted the progress of human civilization, the European Radiological Society, the North American Radiological Society and the American Radiological Society jointly decided to set the date when Roentgen discovered X-rays as "World Radiological Day". Roentgen is also on the "list of the most influential people in history 100" carefully compiled by American scientist Mike H. Hart, and his ranking on the list is 7 1.
2. American doctor Oldendorf founded CT theory.
Readers will ask, "CT" is just two foreign letters. What does this mean?
"CT" is the abbreviation of "Computed Tomography", which means "Computed Tomography". As mentioned above, the basis of CT technology is X-ray, so the more complete name of this technology is "X-ray CT".
As early as 1959, American neurosurgeon Willem Henry Oldendorf (1925-1992) had the idea of scanning people's heads with X-rays. In X-ray tomography, the receiver converts the attenuated X-ray into an electrical signal, then converts the electrical signal into a digital signal and gives it to the computer for calculation, and then performs inverse operation, and then converts the digital signal calculated by the computer into an electrical signal and then converts the electrical signal into an image, so that brain lesions can be examined through the reconstructed image. This is the basic principle of CT.
196 1 year, Oldendorf developed a very rough CT prototype at home. Most parts of the prototype are taken from household garbage, such as his son's toy train, phonograph turntable, alarm clock and so on. He published a paper on this research and applied for a patent in the US Patent Office. 1963 10 In June, the US Patent Office approved Oldendorf's CT patent.
Later, Allen mcleod Kolmark (1924-1998), a professor at Tufts University in Massachusetts, became interested in Oldendorf's CT theory and proposed a new computer algorithm, because the key to transforming CT from theory to clinical application is mathematics.
Oldendorf has found a number of companies that produce CT, but none of them are willing to invest, because the cost of producing this machine is too high, and at that time, many people thought that this machine was of little clinical use. Unable to find a manufacturer, Oldendorf gave up the idea of continuing to promote the commercialization of CT and turned to other scientific research. Unfortunately, Oldendorf is only one step away from pushing CT into clinical application.
To commemorate Oldendorf's outstanding contribution to the establishment of CT theory, the American Neuroimaging Association has established the Oldendorf Prize, which is selected once a year for outstanding contributors in the fields of CT clinical diagnosis, nuclear magnetic resonance, photon scanning and electronic scanning.
Godfrey Newbold Huntsfield, inventor of clinical CT.
3. British EMI Records Company developed clinical CT.
Godfrey Newbold Huntsfield, an engineer of EMI (which also manufactures electronic products), developed the world's first clinical CT in September, 197 1, and installed it at Atkinson-Morley Hospital in Wimbledon near London. On June 65438+1 October1day of that year, he operated this CT together with a doctor in the radiology department, and made a head CT scan for a brain tumor patient and obtained a head image.
In the first clinical CT examination in the world, X-rays scan the skull at an angle of 180 degrees (interval 1 degree), each scan takes about 5 minutes, but it takes 2.5 hours to reconstruct the image by computer. It can be seen that the rapid development of CT later benefited from the development of computers, because it depends on the computing speed of computers.
The clinical CT developed by EMI Records Company was successful and soon put into mass production in the market. The first generation of CT is called "EMI recording scanner". 1973, EMI Records Company won the "Queen's Technological Invention Award" for developing clinical CT.
Some people think that EMI can produce CT because of the Beatles (also known as "Beatles") in the 1960s. Because EMI made a lot of money from the Beatles' record release, it has enough funds to invest in CT research and development and later commercialization. Someone said, "CT was sung by the Beatles."
Huntsfield and Cormac, as co-inventors of clinical CT, won the 1979 Nobel Prize in Physiology or Medicine. But this Nobel Prize is controversial, because Oldendorf, the founder of CT theory, failed to win the prize, and many people wrote articles for him.
4.CT is constantly updated.
As mentioned above, the initial CT scanning speed is very slow, and it is basically only used for brain scanning. 1974, Professor Robert Steven Ledley (1926 -20 12) of Georgetown University School of Medicine in Washington, D.C., developed a whole-body CT. From then on, CT can examine any part of the human body.
1989, spiral CT came out, and the scanning speed was greatly improved. Four-slice spiral CT was born in 1998, that is, the X-ray tube can get four tomographic images at the same time when it goes around the body, which further improves the scanning speed and accuracy.
Spiral CT is relative to conventional CT. The X-ray tube of conventional CT moves back and forth in the scanning frame, that is, the X-ray tube rotates to scan one fault at a time, and then moves forward for a set distance to scan the next fault, and so on, until the part to be scanned is scanned, the cable is used for power supply, which is easy to entangle and difficult to improve the scanning speed. Spiral CT is different. The X-ray tube rotates continuously in the scanning frame and moves forward while rotating, forming a spiral motion, just like screwing a nut on a screw, which greatly improves the scanning speed. At the same time, spiral CT is powered by slip ring, so there is no cable winding problem.
In 2007, Toshiba Corporation of Japan developed 320-slice spiral CT, and 20 10 was upgraded to 640-slice. A CT scan can be completed in one second, and a volume scan is realized. After spiral CT, Shuang Yuan CT and energy spectrum CT are constantly updated.
At present, the main CT manufacturers in the world are Philips in the Netherlands, Siemens in Germany, General Electric in the United States, Toshiba in Japan and Hitachi.
CT is a precise instrument. On CT equipment, the positioning accuracy error of the simplest scanning bed should not exceed 0.1mm. The three-phase AC voltage required for CT is 380 volts, and the positive and negative error is not more than 38 volts; The frequency is 50 Hz, and the positive and negative error is less than 2.5 Hz. Room temperature 18 -22, humidity 40% to 60%.
Now CT is highly intelligent. The operator inputs the basic parameters into the computer, and the computer automatically controls scanning and image reconstruction without manual intervention. Even if there is a general fault in CT, the computer self-checking system will automatically eliminate it. If the self-inspection system can't automatically troubleshoot, it will connect with the maintenance center through the Internet, and the maintenance center will diagnose and troubleshoot the fault remotely.
Head and neck CT angiography (VR)
How did 5.5 do it? CT scans and images?
Ordinary X-ray is a perspective photograph of human organs and tissues superimposed together, which brings certain difficulties to the diagnosis of some diseases. CT is a tomographic scan with no overlapping of human tissues, high image resolution, convenient diagnosis and wide clinical application.
CT consists of three systems, namely scanning system, computer system and image display and storage system. The scanning system is the most complex, and its components include X-ray tube, high-voltage generator, detector, collimator, filter, data acquisition system, scanning frame, scanning bed and so on.
In CT scanning, a certain section of human body is divided into several imaging units, and X-rays rotate around this section. The detector at the other end will receive X-rays attenuated on each imaging unit and convert them into current signals, and then convert these electrical signals into digital signals for the computer to calculate the attenuation value of X-rays on each unit. Then, in turn, the digital signal calculated by the computer is converted into an electrical signal, and then the electrical signal is converted into an optical signal. These optical signals form pixels with different gray levels, and these pixels are arranged in a matrix to form a CT image. CT images can be stored on hard disk, USB flash drive, CD-ROM and other storage media, and of course they can also be printed by laser.
The larger the matrix, the smaller the segmented single pixel area, the finer the imaging and the easier the diagnosis.
Readers may ask, how is the attenuation of X-rays calculated?
The attenuation coefficient of X-rays passing through different substances is different. The x linear attenuation coefficient of water is 1, and the x linear attenuation coefficient of air is close to 0. In order to facilitate the operation in CT scanning, the unit of attenuation coefficient used in CT is "Heinz unit" (Hu, named after the inventor of clinical CT), referred to as "CT value" for short. The CT value of water is 0 Heinz unit, that of air is-1000 Heinz unit, that of dense bone is+1000 Heinz unit, and that of human tissue ranges from-1000 Heinz unit to+1000 Heinz unit, with a span of 2000.
The higher the density of human tissue, the more X-rays absorbed, the greater the CT value, and the reconstructed image is white. Conversely, the lower the density of human tissue, the less X-ray absorption, the smaller the CT value and the darker the reconstructed image. We can see from the CT images that the bone tissue is white and the hollow tissue is black.
6.CT has a variety of scanning methods, which can get stereoscopic images.
CT scanning has many modes to choose from, just like taking photos with smart phones. For example, "Std" mode is mainly used for routine scanning of chest, abdomen and pelvis; "Soft" mode is mainly used for organ scanning with similar density; "Lung" mode is mainly used for lung scanning; The "detail" mode is mainly used for posterior scanning of spinal cord; "Bone" mode is mainly used for bone detail scanning; "Edge" mode is mainly used to scan small bones in the head; "Bone plus" mode is mainly used for head detail scanning; "CE" mode is mainly used for angiography.
Because CT is a tomographic scan, there is a problem of choosing the thickness of the fault. The thinner the fault thickness, the better the longitudinal continuity of the image and the higher the longitudinal spatial resolution. However, this does not mean that the finer the scanning fault, the better. This mainly depends on the examination site and the nature of the lesion, because if the fault is too thin, the detector will receive fewer X-ray photons, thus reducing the resolution. The fault thickness is usually set between a few tenths of a millimeter and a few millimeters. The smaller the scanning organ, the smaller the slice thickness; On the contrary, the larger the scanned organ, the greater the layer thickness.
Readers can imagine that although CT is a tomographic scan, if these tomographic images are superimposed in turn, a three-dimensional image can be obtained, which is the so-called "volume scan". With volume scanning, analog imaging can be realized, that is, the internal situation of human organs can be clearly observed through CT without endoscope.
7.CT examination has certain risks.
The harm of CT examination to patients mainly comes from X-rays, which can cause cancer, and CT examination is the largest dose of X-rays in all kinds of imaging examinations. The X-ray dose of standard mode CT scan is 700 times that of chest film, which is equivalent to the sum of X-ray dose absorbed by people in natural environment for two years. The more frequent CT examination, the greater the possibility of cancer.
2065438+In March 2003, the website of Harvard Medical College published a document, saying that there are 70 million CT clinical examinations in the United States every year, many of which are unnecessary. The article advises patients to avoid CT examination as much as possible and choose alternative examination methods if possible.
The American Radiological Society suggests that the dose of X-ray medical examination received by a person in his life should not exceed 100 millisieverts, which is roughly equivalent to 25 standard mode CT examinations. When conducting examinations such as cancer treatment, the X-ray dose of a CT examination will exceed 100 millisieverts, which means that while trying to treat existing cancers, it is also inducing the formation of new cancers.
Of course, because it takes a certain period to get cancer after X-ray irradiation, the younger you are, the greater the possibility of getting cancer after CT examination. People over 65 years old are unlikely to get cancer after CT examination, because it takes about 20 years for X-rays to induce cancer. If they don't have a CT examination until they are 65, they will have to wait 20 years to get cancer. By this time, they were 85 years old and probably died before they got cancer.
X-ray dose is directly proportional to image quality, which requires a compromise between X-ray dose and image quality. We should not blindly pursue image quality and increase X-ray dose, which will cause unnecessary harm to patients' health.
Attention should also be paid to the protection of gonads, thyroid gland and eyes during CT examination, and pregnant women and babies should not receive CT examination.
In addition, when enhanced CT scanning, some patients will have allergic reaction to the contrast agent, and at the same time, the contrast agent will also cause damage to the kidney.
In view of the certain risks of CT examination, the public should understand these common sense, and doctors have the responsibility to explain the advantages and disadvantages of CT examination to patients, avoid abusing CT examination, and reduce the economic burden and health risks of patients.
Text, part of a picture/width