Four seas network: we always like to say that mobile phones, microwave ovens, electromagnetic ovens, electric blankets, and even routers have radiation. In fact, the radiation of these substances refers to the electromagnetic radiation. The harm of electromagnetic radiation to human body is very limited. So, what kind of radiation can cause serious harm to human body? That's ionizing radiation.
The damage of medical X-ray radiation to human body is within the controllable range. What about MRI? Let's listen to "nuclear"!!! Is nuclear radiation more dangerous! Yes! Nuclear radiation is more dangerous than medical X-ray and more serious to human body! However, there is no nuclear radiation in NMR. Although there is a 'nucleus', this' nucleus' is an atomic nucleus (hydrogen proton nucleus), and there is no ionizing radiation.
So what is the basic principle or mechanism of NMR?
Simply speaking, it is to use the RF pulse to excite the low-energy hydrogen protons to obtain energy transition to the high-energy level. The high-energy hydrogen protons release energy unsteadily back to the low-energy level. Collecting this part of the released energy is the signal! This signal is processed to be a magnetic resonance image. It can be seen from the above expression that the only external factor is RF pulse. Is RF pulse harmful?
The essence of RF pulse is electromagnetic wave. In the process of MRI image acquisition, the transmitted RF pulse is electromagnetic wave with different frequency. Maybe someone has to say that electromagnetic wave must also be harmful! You are right, but not right either! In fact, electromagnetic waves are all around us all the time. The most common is the transmission and reception of mobile phone signals, which are all transmitted by electromagnetic waves. Do you think he has any harm? There must be. Compared with the 24-hour mobile phone around you, the electromagnetic radiation of MRI can be ignored!
Therefore, MRI can be used for fetal examination just like B ultrasound.
The electromagnetic wave of RF pulse is harmless in a certain range. Everything has a degree. The damage of medical X-ray to human body is controllable, which is a degree. If it exceeds this degree, the damage of medical X-ray to human body is very obvious! If you have to give an example, let's give an example of eating. It's OK to eat properly. If you eat too much and eat too much, it must be bad for your health! But we can't say that eating is harmful to our health!
In the actual examination, there are also the following situations that may cause potential harm to human body:
1. There is also a 'noise' hazard, which will cause some damage to the hearing. Of course, this damage is caused without any protective measures. In the work of the examination, the earplugs and earphones of the examinee will be given double protection, and the examinee's hearing can be completely protected!
2. Fever: because the RF pulse acts on the human body, the human body will deposit heat. The higher the field strength is, the more obvious the effect is. So people with fever can't do 3.0T MRI.
3. Metal foreign bodies, whether in vivo or in vitro, can be avoided as long as they abide by the rules.
In short, the main harm of MRI to the body is the harm of electromagnetic wave, heat deposition and noise (negligible), and there is no so-called nuclear radiation or X-ray radiation!