When a patient goes to the hospital to see a doctor, the doctor usually first asks about his medical history, conducts a physical examination, measures his body temperature, respiration, heart rate, blood pressure, and tests his blood. Some diseases can be diagnosed from the appearance on the body surface, but the diseases in the body cannot be directly "seen" outside the body. For the internal conditions of the body, doctors use various medical instruments to diagnose and determine whether there is any disease in the organs in the body. In this regard, doctors most commonly use medical imaging technology, that is, using medical imaging equipment to "take pictures" of the internal conditions of the patient's body, and diagnose diseases in the body based on the images obtained by "taking pictures". Most of these instruments perform diagnosis outside the body and are not harmful to the human body.
Therefore, the role of medical imaging is to image the internal structure and function of the human body with or without damage, and to provide three-dimensional, static or dynamic images of the internal body, thereby diagnosing the internal health of the human body. situation. The internal structure and functions of the human body are very complex. It is not easy to image the internal conditions of the human body without damage. This specialized subject is called medical imaging. The expertise in this area is called medical imaging technology. This is a type of high technology that is developing rapidly and is closely related to protecting the health of the people.
The scope of modern imaging includes: conventional X-ray diagnosis, X-ray angiography, DSA digital subtraction angiography, CT (X-ray computed tomography); ultrasound imaging includes B-ultrasound; MRI magnetic** *Vibration imaging; nuclear medicine including ECT.
Principle of X-ray imaging:
X-rays are high-energy light that can penetrate many materials, including human tissue. When X-rays pass through the human body, they interact with the materials inside the body, causing part of the X-rays to be scattered or absorbed, and the remaining X-rays can pass through the body, and the intensity of the X-rays passing through the human body is weakened. It is precisely because the penetration intensity of X-rays when passing through different parts of the human body is different. On the X-ray film that records the penetrated X-rays outside the body, there are different exposures. The "projection" image recorded on the film will show Images of different shades. In this way, using X-rays to see through the human body or "take pictures" of the human body can also diagnose lesions within the human body. Doctors use the above characteristics of X-rays to understand the internal structure of the human body.
DSA digital subtraction angiography is a new technology that combines electronic computer and conventional X-ray cardiovascular angiography. X-ray CT means X-ray computed tomography. When performing an X-ray CT scan, X-rays are used outside the human body to illuminate and scan the human body at different angles. Multiple projection images are obtained, and computer processing methods are used to form a three-dimensional image.
Ultrasound imaging
Uses the physical properties of ultrasound to interact with the acoustic properties of human tissues and organs to generate information, which is collected and processed to form images. Ultrasound diagnosis has good intuitive performance, high detection rate, simple operation, rapid diagnosis, especially high sensitivity for the diagnosis of congenital malformations, so it is very popular. It is widely used in clinical obstetrics and gynecology. Pregnant women are generally between 20 and 22 months pregnant. Ultrasound examination is done every 1 week. At this time, the whole fetus and internal structure can be displayed, and fetal malformations can be diagnosed. Color B-ultrasound can also diagnose heart and large blood vessel malformations.
Principles of medical MRI imaging
Different from X-ray photography and CT, it uses hydrogen protons (H) in water present in large amounts in the human body to perform imaging. A single proton is positively charged and can rotate around its own axis, which is called spin. To facilitate understanding, the rotation of the proton is often compared to the top that many people played with as children. When it is in a vertical state when rotating at high speed, if you whip it gently with a whip, it will deviate from the axis, and then gradually return to the upright rotating state.
There are countless hydrogen protons in the human body. Due to their chaotic directions, the mutual magnetic fields cancel each other and do not show any magnetic field to the outside world. It is like a group of naughty children making noisy and running around on the playground. Now the teacher needs to arrange them into team, so how to queue hydrogen protons? If the human body is placed in a strong magnetic field, the situation will change dramatically. At this time, the protons that make up the human body, like small magnetic rods, will temporarily follow the direction of the magnetic field. Arranged to form a large magnetic rod. By arranging the protons into a queue, the signal emitted is large enough to be detected by the instrument, which is then processed by a computer to produce an image of the human body.
Nuclear medicine imaging:
It is based on the ingestion of radioactive substances (imaging agents) through the organs. Due to the differences between normal tissues and lesions between target organs and non-target organs, There are differences in tissue distribution. Selective uptake by target organs, selective uptake by diseased tissue cells, or non-uptake due to lack of normal functions will lead to significant differences in the distribution of imaging agents. First, radioactive drugs are injected intravenously, and then an instrument is used to collect nuclear ray information emitted from inside the target organ, and a computer is used to form an image based on the density of the rays emitted from each part. This image directly reflects the functions of cells in each part of the organ, so it is called " "Functional Imaging"
The general public is concerned about the cost of the examination, the rationality of the examination, and the damage and consequences to the human body. This involves many factors: such as the doctor-patient relationship, hospital level, the diagnostic skill level of the attending physician, the patient's income level, etc. For professional radiologists it involves ‘comparative imaging’. It is necessary for both doctors and patients to understand the selection principles of comprehensive imaging. Sometimes patients do not understand and think that the doctor is abusing the examination. This requires a communication issue. The doctor should explain the imaging lesions to the patient or family to gain their understanding. This also involves the issue of the patient's right to know. .