During the epidemic period, we can often see the airport, railway station staff using thermal imager screening fever. In fact, the thermal imager can also be used for the diagnosis of some other diseases. Besides thermal imager, X-ray, CT and MRI are also common medical imaging technologies. There are some interesting stories behind the invention of these technologies. Let’s take a look at them.

Infrared imaging technology appeared in the 1930s. People use alkali metal or semiconductor cathode in high vacuum to convert infrared radiation into electronic radiation, and then convert electronic image into optical image that can be seen by human eyes through fluorescent screen. This technology was mainly used to equip the army in the early days. At the end of World War II, German and American troops were equipped with infrared night vision devices. After decades of development, thermal imaging equipment has been widely used in construction, fire protection, medicine, industrial production and many other fields.

The application of thermal imager in medicine can be traced back to 1956. Through thermal imager, British doctor Lawson found that the temperature of breast skin with breast cancer was higher than that of normal skin; he also found that the temperature of tumor blood vessels was higher than that of normal blood vessels. Since the 1970s, thermal imaging technology has become a conventional diagnostic technology, which is an important means of examination for tumor, acute and chronic inflammation, and limb blood supply. In the field of prevention, the thermal imager can be used for rapid body temperature screening of a large range of people. For example, in the process of epidemic prevention and control, the thermal imager shows its skills.

In fact, these thermal imagers equipped in public places do not belong to medical instruments. Generally, there is a temperature measurement error of ± 0.5 ℃. Therefore, the suspected fever patients screened out need to use a thermometer to further measure their body temperature. Even so, the thermal imager has greatly improved the efficiency of prevention and control work. X-ray imaging technology was used in medical practice almost at the same time when it was invented. At that time, people did not know the harm of radiation, so there were no protective measures.

What are X-ray, CT, MRI and thermal imager? The story of medical imaging technology

In addition to the general perspective diagnosis, people have also developed a variety of uses, such as pain relief, beauty, abstinence addiction, and even just as a commercial gimmick to attract curious consumers. The abuse of X-ray did not gradually disappear until after the 1950s. Today, X-ray diagnosis process has been very standardized. As long as long as long-term exposure is avoided, X-ray examination is relatively safe. X-ray is still a commonly used imaging method, with its unique advantages: convenient, cheap, suitable for disease screening, bone and joint diseases and foreign body obstruction examination, etc.

With X-ray examination, people can finally check the internal structure of the body noninvasively. However, X-ray has an obvious disadvantage: the image of the lesion is easily interfered by the image of the adjacent normal tissue, and the image of the body organ overlaps, so it is difficult to distinguish.

After more than ten years of research, Cormac found out a practical mathematical method of image reconstruction. Since 1967, hunsfeld, a British computer expert, has gradually put the theory into practice. He tried to take X-rays from different directions and integrate the data through a computer. After several years of optimization and improvement, the world’s first CT instrument was born in 1972. CT is the abbreviation of computed tomography.

With the emergence of CT technology, medicine has ushered in a new era. Cormac and hunsfield won the 1979 Nobel Prize in physiology and medicine. Nowadays, CT has been used in the diagnosis of various system diseases of the human body, playing a very important role.

MRI (magnetic resonance imaging) is not only magnetic resonance imaging. It uses a special magnetic field to excite the resonance effect of hydrogen nuclei in human tissues. The process of hydrogen nucleus transition from resonance state to natural state (also known as relaxation process) will release energy. After the detector receives this part of energy signal, the computer will reconstruct the image according to a certain algorithm.

Later, British scientist Peter Mansfield used gradient magnetic field to convert resonance signals into images more quickly and accurately. More than half of the body’s components are water, and people immediately realized that this technology could be used to detect the structure of the human body. In the early 1980s, with the gradual improvement of resolution, MRI began to be used in clinical practice. In 2003, Paul lauterberg and Peter Mansfield won the Nobel Prize in physiology and medicine.

CT and MRI are often compared together. In fact, they have their own advantages. CT has the advantages of high speed, low price and good imaging effect on bone, but it has radiation and poor imaging effect on muscle, ligament and other soft tissues. MRI is safe and radiation-free, and has good imaging effect on soft tissue; however, MRI detection is time-consuming and expensive, and it is not suitable for patients with implanted metal (such as cardiac pacemaker). In general, the choice of CT or MRI is still to listen to the advice of professional doctors.

With the rapid development of medical imaging technology, in addition to the above, ultrasound medicine, nuclear medicine, interventional medicine and so on are our weapons to fight diseases and “insight” to know ourselves. I believe that with the continuous development of science and technology, we will see more and more advanced technology for medical diagnosis and treatment.


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