In the medical imaging department, there are often some patients with MRI (MR) “emergency list” to do the examination, and say that they need to do it immediately. For this emergency, the imaging doctor often says, “Please make an appointment first”. What is the reason?
First, let’s look at the contraindications:
First,Absolute contraindications
1. Patients with cardiac pacemakers, neurostimulators, artificial metal heart valves, etc.;
2. With an aneurysm clip (except for paramagnetism, such as titanium alloy);
3. People with intraocular metal foreign bodies, inner ear implants, metal prosthesis, metal prostheses, metal joints, and ferromagnetic foreign bodies in the body;
4. Early pregnancy within three months of pregnancy;
5. Patients with severe high fever.
So, what is the reason why MRI does not carry metal?
First, there is a strong magnetic field in the MRI machine room, which can cause the metal shift and cause the metal objects to fly to the equipment center and cause harm to patients.
Second, the powerful MRI RF field can produce thermal effect, thus causing the heating of metal substances, MRI examination, too close to the magnetic field, or in the magnetic field can cause local tissue burns or even endanger the life of patients.
Third, only a stable and uniform magnetic field can obtain a clear image. When checked with metal substances, local artifacts can be produced in the metal site, which affects the uniformity of the magnetic field and cannot clearly display the signal contrast of surrounding normal tissues and abnormal tissues, which affects the diagnosis of disease.
Second,Relative contraindications
1. Patients with metal foreign bodies (metal implants, dentures, contraceptive rings), insulin pumps, etc., who must undergo MR Examination, should be careful or check after removal;
2. Critically ill patients requiring the use of life support systems;
3. Patients with epilepsy (MRI should be performed under the premise of full control of symptoms);
4. For claustrophobic patients, if MR Examination is necessary, it should be carried out after giving an appropriate amount of sedative;
5. Patients with difficulty in cooperation, such as children, should be given appropriate sedatives after;
6. Pregnant women and infants should be examined with the consent of the doctor, the patient and the family.
Third, what is the relationship between these taboos and not doing emergency nuclear magnetism?
First, emergency patients are in critical condition and will use ECG monitoring, respiratory monitoring and other instruments at any time, and most of these devices can not be brought into the magnetic resonance room, and forced inspection has huge risks in protecting the life safety of patients.
Second, compared with CT examination, MRI scan time is longer, the fastest skull examination also takes at least 10 minutes, other parts of the examination time is longer. Therefore, for critically ill patients with symptoms of unconsciousness, coma, lethargy, or agitation, it is difficult to complete MRI in this condition.
Third, MRI can be dangerous for patients who cannot accurately describe their previous surgery or other medical history.
Fourth, for emergency patients who encounter car accidents, smashing injuries, falls, etc., to minimize the movement of patients, in the absence of reliable inspection support, doctors can not determine whether the patient has fractures, internal organs rupture and bleeding, and can not confirm whether there are metal foreign bodies caused by trauma. CT examination is more appropriate for patients with this condition to help save patients in the first time.
Therefore, due to the particularity of MRI examination, emergency patients in critical condition must wait for stable condition and department evaluation before MRI examination, and it is also hoped that the majority of patients can give more understanding.
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Post time: Mar-11-2024
