The doctor opens an image examination. Why is it so open?

Who will not go to the hospital for a lifetime? When going to the hospital, doctors will often give you all kinds of imaging examinations, such as ultrasound, CT, MRI, etc. You may be puzzled in your heart. Why did you choose this kind of examination for me for so many kinds of examinations? Is it just that the more expensive the better? It is precisely because many people may have such doubts that the common sense I am talking about here is expected to be helpful to you.

First, how to choose for imaging examination, here is a concise version, not to reason in detail, but to be practical:

Traumatic bone: rough X-ray film, closer CT, MRI can’t see clearly;

Cervical spine and lumbar spine: the best MRI and the second CT;

Brain and spinal cord: MRI is seen for cerebral infarction, CT is seen for hemorrhage, and MRI is the best for most of the rest, including brain tumors.

Chest: roughly understand the X-ray film, carefully analyze and select CT, generally do not choose MRI when looking at the lung, and only say below the heart;

Abdomen and pelvic cavity: except intestinal tract, viscera can be generally ultrasound, CT and MRI have their own advantages;

Heart: CT can be selected for patients with high-risk chest pain to exclude coronary heart disease. Ultrasound can be used to see the heart itself, and MRI is better.

After reading these lines of words, I believe you can answer all the doubts you may have when you see a doctor. Below, if you are interested, let’s have a detailed chat together.

Second, what are these inspections

Common X-ray films, commonly known as [X-ray], are images obtained by penetrating human body with X-ray. They are widely used in routine examination of bones, chest and cervical vertebrae and lumbar vertebrae. The advantages are fast examination and low price. The disadvantage is that the diagnosis has limitations due to overlapping plane imaging of human tissues.

Barium meal: i.e. Gastrointestinal X-ray examination. Through the introduction of barium, doctors complete the examination of common gastrointestinal diseases under fluoroscopy and spot films.

CT (computed tomography): means X-ray computed tomography, which is to use X-ray to scan a certain part of the human body to obtain the cross-section of the examined part of the human body, or to generate stereoscopic images after processing. Through various technologies, CT examination can provide clearer and multi-faceted image information to the human body structure, including widely used CT angiography, etc. CT examination is fast and accurate, but the radiation is large.

Ultrasound: Diagnosis of the principle of echo generated by ultrasound. The most common of them is B-ultrasound examination. B-ultrasound is 2-dimensional information. Form a plane figure to reflect the structure of the human body. Color Doppler ultrasound, which uses Doppler ultrasound technology, provides rich information on hemodynamics in blood vessels. Ultrasound examination is radiation-free, very safe, and even suitable for prenatal examination of pregnant women. However, ultrasound penetration is weak and has limitations on some pathological changes.

MRI (magnetic resonance imaging): MRI has the advantages of no radiation, high tissue resolution and multiplanar imaging. MRI is especially accurate in the diagnosis of brain, spinal cord, pelvic organs, cardiac macroangiopathy and myocardial infarction. However, MRI is strictly forbidden for patients with metal implants (such as cardiac pacemakers, mechanical cardiac valves, aneurysm clips, vascular stents, artificial joints, and metal internal fixation). Unless the material specification specifically indicates that MRI examination is acceptable. In addition to the high price, the disadvantages include long examination time, loud noise and small space. MRI examination is not recommended for patients who cannot cooperate (such as children, delirious and claustrophobic patients).

PET/CT: It is a new technology that combines positron emission tomography with conventional CT. At the same time of examining the structure, it also evaluates the metabolic function of cells. Combining the evaluation of structure and function, it is of great significance in evaluating myocardial survival and localization of brain epilepsy foci. In recent years, it has been widely used, especially for tumor screening and localization. The disadvantage is that the equipment and isotopes are expensive and have radiation.

Three, common diseases will probably do what tests?

All kinds of trauma, suspected injury to bones, X-ray film is fast and easy to obtain, should be the first choice; For further and more detailed observation, CT can be selected. Ultrasound and MRI cannot clearly see bone, cortex and medulla, and the effect is far less than that of X-ray-based X-ray films and CT.

For disc diseases (cervical spondylosis, lumbar disc herniation, etc.), CT is the fastest and most convenient examination method. If we need to better observe these soft tissues such as spinal cord nerves, the best choice is naturally MRI. Similarly, MRI is also the first choice for the examination of joints, muscles and adipose tissues.

For brain and spinal cord diseases, MRI has the strongest soft tissue resolution, Clear 3D images can be obtained directly, Different sequences are used to obtain more comprehensive diagnostic information. However, for hemorrhagic stroke (such as [cerebral hemorrhage]), CT examination under emergency conditions can find abnormalities at the earliest and get diagnosis at the early stage. However, MRI can find abnormalities earlier than CT for ischemic stroke (cerebral infarction), so it is often impossible to exclude cerebral infarction if only CT is performed at the early stage without finding abnormalities.

X-ray chest films can roughly examine the heart, aorta, lung, pleura, ribs, etc. As can be seen, Cardiac shadow increased, lung texture increased, lung calcification points, aortic nodal calcification, etc. Compared with X-ray, Chest CT examination showed clearer structure, The sensitivity and accuracy of detecting chest lesions are better than those of conventional X-ray chest films. In particular, it is of decisive significance for the diagnosis of early lung cancer. High-resolution CT further increases the resolution of lung observation and is of great significance for some diseases (such as pulmonary interstitial diseases). However, the radiation dose of CT examination is significantly higher than that of X-ray. MRI has very limited application in the diagnosis of lung diseases.

The diagnosis of gallbladder disease relies heavily on ultrasound, It is superior to CT and MRI. This is mainly because, Abdominal organs are affected by respiration, Exercise is large, which affects CT and MRI imaging, but ultrasound will not be affected. At the same time, ultrasound has high diagnostic accuracy for liver, spleen, pancreas, kidney, pelvic organs, etc. Under the examination of experienced ultrasound doctors, the accuracy is no less than CT and MRI. However, ultrasound is greatly interfered by gas, so for intestinal tract and other areas with more gas, ultrasound diagnostic accuracy is greatly reduced.

Imaging examination of the heart is mainly to examine coronary artery, myocardium, pericardium and other structures.

Coronary artery stenosis reaches a certain limit, What we usually call coronary heart disease. Examining coronary arteries, The best [gold standard] is actually coronary angiography performed after hospitalization. However, hospitalization is required. It also requires contrast agents in the arteries, There is a risk of inverted contrast agent nephropathy, Therefore, sometimes CT can be used instead for high-risk patients. CT is used to examine coronary arteries. If stenosis is not found, coronary heart disease can be well excluded. However, it is more disturbed (such as calcification), Especially for elderly patients, The calcification of coronary arteries was more severe, Therefore, the observed stenosis cannot be directly understood as the existence of stenosis and needs further evaluation. In a word, CT is more accurate for exclusion, and doctors themselves dare not be 100% for diagnosis. Finally, it should be mentioned that coronary artery CT examination has a large amount of radiation and is not suitable for general routine physical examination. Although MRI has no electromagnetic radiation, the observation of coronary artery is far less than CT.

Cardiac MRI is the [gold standard] for evaluating the structure and function of the heart. However, as a routine examination of the structure and function of the heart, the information provided by cardiac color Doppler ultrasound is relatively sufficient, simple and easy to implement, and is a more commonly used method.

IV. Summary

After talking so much, I hope to make two things clear:

A. Different parts and different observation emphases have different imaging examination methods. B. It is not that the more expensive the examination, the more suitable it is for you. C. Each examination method has its advantages and disadvantages. Doctors will choose one or more optimal examination methods according to your specific condition to achieve the purpose of accurate diagnosis.

This article is reproduced under the authorization of Dr. Zhai Guangyao of Beijing Anzhen Hospital Cardiology Center.