Many people can’t tell the difference between X-rays, CT, ultrasound, and MRI, which are commonly used imaging tests. Now, comparing the body to food, show you how these tests play different roles. X-rays: like flattening bread to see X-rays will pass through the body and encounter an obscured area that will not be exposed on the negative, and the area will be white after the film is washed. The biggest disadvantage of X-rays is that they are limited by the overlap and concealment of images of deep and shallow tissues, and sometimes require multiple X-ray shots from multiple angles. CT: like slicing bread CT examination principle is that the X-ray will be layered through the body, after the computer calculates the secondary imaging, like slicing a piece of bread to see. The advantage is that it can be viewed in layers, and after calculation, more tissue information can be displayed. Ultrasound: like picking a watermelon before knocking The principle of ultrasound is to use ultrasound to penetrate the body, when the sound waves encounter human tissue will produce reflected waves, through the calculation of reflected waves imaging. It is like picking a watermelon, knocking while looking at it to show the condition of the lesion. MRI: Shake it and see it again The principle of MRI (magnetic resonance imaging) development is described below. The MRI machine uses a stronger magnetic field to make the magnetic lines of force of all water molecules in the body in the same direction. At this time, the magnetic field of the MRI machine suddenly disappears, and the magnetic lines of force of the water molecules in the body suddenly return to the original randomly arranged state. Repeatedly apply the magnetic field and suddenly disappear, the MRI machine will get sufficient data and computing after imaging. Simply put, it is equivalent to shaking your hand to make the water molecules vibrate, then calm down and feel the vibration inside. Therefore, MRI is also jokingly referred to as a shake and see test. What kind of tests are used for each of the four imaging modalities? Doctors often order a variety of imaging tests: ultrasound, CT, and MRI. …… Many patients may question their doctor’s intention to order a high-cost test. In fact, doctors choose different imaging tests according to different conditions. 1, trauma bone – a rough look at the X-ray film, a closer look at CT, nuclear magnetic can not see a variety of trauma, if you suspect that the injury to the bone, the priority choice of X-ray photos, test results quickly and easily. If you want to further observation, you can choose CT. ultrasound, nuclear magnetic for the bone cortex medulla, etc. do not see very clear, generally do not choose. 2, cervical lumbar spine – the best choice of MRI, the second choice of CT cervical spondylosis, lumbar disc herniation and other intervertebral disc disease need to observe the disc and the corresponding nerve roots, to better observe these soft tissues, the best choice is the MRI. Similarly, for joint, muscle and fat tissue examination, MRI is also preferred. 3, chest – a cursory look at the X-ray film, a closer look at the CT, look at the lungs do not choose the MRI X-ray chest film can be a cursory examination of the heart, aorta, lungs, pleura, ribs, etc., can be checked for increased lung texture, lung calcification points, aortic node calcification, etc.. CT chest examination shows a clearer structure and is more sensitive than conventional X-ray chest film in detecting lesions in the chest and showing the accuracy of lesions, especially for early lung cancer diagnosis. However, the radiation dose of CT examination is higher than that of X-ray. The application of MRI for the diagnosis of lung diseases is very limited. 4.Abdominal pelvis – except for the intestines, general ultrasound can be investigated The abdominal organs are more affected by breathing, which in turn affects CT and MRI imaging, while ultrasound will not be affected by this. At the same time, ultrasound has a high diagnostic accuracy for liver, spleen, pancreas, kidney, pelvic organs, etc. However, ultrasound is greatly disturbed by gas, and the diagnostic accuracy of ultrasound will be reduced for organs containing more gas, such as the intestines. 5, heart – exclude coronary heart disease with CT, look at the heart function with ultrasound Conventional heart structure and function of the examination, the information provided by the heart ultrasound has been more adequate, and simple and easy. With CT can check the coronary arteries, but coronary CT examination radiation is large, not suitable as a routine physical examination. Although MRI is free of electromagnetic radiation, it is not as good as CT for coronary artery observation, and cardiac MRI is the “gold standard” for evaluating the structure and function of the heart.