1, magnetic vibration and CT radiation problems
Today, I want to correct this view. The English word for magnetic resonance imaging is: magnetic resonance imaging, which is literally translated as magnetic resonance imaging, or MRI for short. There is no mention of "nuclear", but why is it called magnetic resonance imaging? Because the imaging principle of nuclear magnetic resonance (NMR) is to use magnetic field to discharge the nucleus of human body, and this process does not release huge energy like the nuclear reaction of nuclear weapons, so there is no electromagnetic radiation in NMR.
Computed tomography: Computed tomography. Because X-rays are used, CT has electromagnetic radiation. Generally, CT examination is not arranged for children and pregnant women.
2. Which is more accurate, magnetic vibration or CT examination?
The advantage of magnetic vibration is that it can distinguish soft tissue more clearly, especially some small lesions such as tumors, and it can be easier to determine whether it is cancer, but the disadvantages are also obvious: ① The examination is too slow, and the CT scan of the same part ends in less than one minute, while magnetic vibration takes half an hour, which is why magnetic vibration has to queue for a long time: too slow! Magnetic vibration is more clear for the examination of static parts, and the examination images of active parts will be pasted (just like moving when taking pictures), so magnetic vibration is more applied to relatively static parts, such as brain, spinal cord, liver, pancreas, pelvic cavity, urinary system, bones and joints, etc. , but rarely used in the lungs, gastrointestinal tract and other parts that are difficult to control their activities, and it is difficult to give children magnetic vibration. Secondly, there should be no metal on the subject, and patients with pacemakers, birth control rings and dentures can't do magnetic resonance examination, which not only interferes with the examination results, but also is very dangerous; ③ Expensive, which is related to equipment price, maintenance cost and inspection efficiency.
The advantage of CT is fast and accurate, even in the lungs and gastrointestinal tract, it can also have a clear imaging effect. Of course, it is best to hold your breath when doing CT. Emergency patients usually arrange CT, even for cerebral hemorrhage, because it is difficult for patients to stay inactive for a long time under very uncomfortable conditions. The disadvantage of CT is that the resolution of soft tissue is lower than that of magnetic vibration, especially for small lesions. Bone and metal will produce artifacts on CT to interfere with image clarity, so the advantages of magnetic vibration are more obvious in the head and spinal cord, which are wrapped by bones.
3. Why should rectal cancer do magnetic resonance and colon cancer not?
① For the reasons mentioned above, magnetic vibration is afraid of "moving". The rectum is adjacent to the anus, located in the pelvic cavity, surrounded by soft tissues and muscles, with low mobility, while the colon is in the abdominal cavity, with high mobility. In order to reduce intestinal peristalsis, anisodamine can be injected temporarily during rectal magnetic vibration, and the imaging effect is more satisfactory.
② The rectum is close to the anus, so the operation is difficult, which involves issues such as whether to keep the anus during the operation and the evaluation of anal function after the operation, and needs more detailed evaluation. For small tumors in the middle and lower rectum, it can also play the role of intracavitary ultrasound.
③ The proportion of liver and lung metastasis in advanced colorectal cancer is high. Therefore, for patients with rectal cancer, we make comprehensive use of the respective advantages of magnetic resonance imaging and CT, and choose the examination method of chest and abdomen CT+ pelvic magnetic resonance imaging. For colon cancer, we choose chest and abdomen CT examination.
Therefore, every technology is not perfect. What we doctors need to do is to fully understand the advantages and disadvantages of each examination and choose the examination that is most suitable for patients.