Let you know about MRI

Author: Li Danfei Song Jian Sichuan Academy of Medical Sciences Sichuan Provincial People's Hospital

Reviewer: Dong Xiaoqiu, Professor of the Fourth Affiliated Hospital of Harbin Medical University

When ordinary people go to the hospital for treatment, they often need to undergo many imaging examinations, such as CT, MRI, etc. Many ordinary people only know about "taking X-rays" and don't know what CT and MRI are. Here is an introduction to MRI.

What is MRI?

MRI, the full name of which is magnetic resonance imaging, is an examination technology that uses the magnetic resonance phenomenon to obtain electromagnetic signals from the human body and reconstruct human body information. The entire MRI process does not involve X-rays, so there is no radiation risk, and patients who are worried about radiation can use it with confidence. In addition, MRI also has the characteristics of multi-directional, multi-parameter, and multi-sequence imaging, and has high resolution. It is currently widely used in clinical examinations.

Figure 1~Figure 2 Copyright images, no permission to reprint

How does MRI diagnose disease?

The tissue structure of the human body is different, so the information obtained by the magnetic resonance imaging machine is also different. MRI images are mainly divided into T1 and T2 signals. The higher the T1 signal and the whiter the T1 image, the more fat and protein the lesion contains; the higher the T2 signal and the whiter the T2 image, the more water the lesion contains. Because the composition of the lesion is usually complex, it shows a variety of complex signals. When different signals appear in a normal image, it may mean that there is a lesion in the organ and further examination or treatment is needed.

What are the indications for MRI?

The indications of MRI include lesions of the nervous system, cardiovascular system, abdominal organs, pelvic organs, and bone and joints. Because MRI is widely used in lesions of the nervous system, it is significantly better than CT in the diagnosis of hyperacute cerebral infarction. MRI can find lesions within 2 hours, while CT at this time often does not show any abnormal findings. Therefore, it is believed that MRI has won precious time for the rescue of cerebral infarction.

What are the special projects of MRI?

MRI's featured items include DWI (diffusion-weighted imaging), MRA (magnetic resonance angiography), MRV (magnetic resonance venography), SWI (susceptibility-weighted imaging), PWI (perfusion-weighted imaging), MRS (magnetic resonance spectroscopy), DTI (diffusion tensor imaging), MRTA (neurovascular imaging) and MRCP (magnetic resonance pancreaticocholangiography), etc. DWI is mainly used for the diagnosis of cerebral infarction, MRA is mainly used for the diagnosis of vascular blockage, MRV is mainly used for the diagnosis of venous thrombosis, SWI is mainly used for the diagnosis of microbleeding in the brain, PWI is mainly used for the diagnosis of cerebral infarction and brain tumors, MRS and DTI are mainly used for the diagnosis of brain tumors, MRTA is mainly used for the diagnosis of trigeminal neuralgia and hemifacial spasm, and MRCP is mainly used for the diagnosis of bile duct stones.

MRA

Figures 3 to 9 are copyrighted images and are not reproduced without permission.

What are the precautions for MRI?

Precautions for MRI include: ① The examiner and the accompanying personnel cannot enter the examination room or accompany the examination if they have the following conditions: pacemakers, insulin pumps, endotracheal intubation, artificial heart valves, intravascular metal stents, aneurysm clips (non-paramagnetic, such as titanium alloys), metal stents after vascular surgery, artificial corneas, metal prostheses and other paramagnetic materials, as well as women in early pregnancy. ② Children, unconscious and other uncooperative patients need to use sedatives and be accompanied by healthy family members. Critically ill patients need to be accompanied by clinical doctors. Patients who are agitated and unable to cooperate need to be treated by the clinical department before the examination. ③ Patients undergoing abdominal MRI should not undergo gastrointestinal barium meal examination one week before the examination and fast for 4 hours before MRI; patients undergoing pelvic MRI should fast for 4 hours before the examination and retain urine for 2 hours before the examination. ④ Patients with severe renal insufficiency should not undergo enhanced examination.

MRI is a common examination for ordinary people. The above is a brief introduction to it. I hope it will be helpful to you. Good health is what people want. Health examination can prevent diseases before they happen. It can treat and adjust the disease before it develops to a point where there is no cure. I hope MRI can really help you.