Anyone who has ever been to a hospital knows that doctors need to have patients undergo a series of tests before diagnosing a disease. The more common tests are X-rays, CT, ultrasound, MRI, etc. Most non-medical people can’t tell what they do? And what is the difference between them? Today we have to popularize it, so that we are clear, these checkups, are checking what, why and check. When it comes to CT, we have to talk about X-ray, X-ray film is what we usually call “filming”, X-ray film has a very strong penetrating ability, the examination is like a plane image of the body’s internal photographs, X-ray examination of the human body is like a whole person squashed like the three-dimensional three-dimensional person squashed in the plane, a variety of structures are reunited. Although the name of CT is different from that of X-ray, CT uses X-ray to irradiate the human body, except that ordinary X-ray only takes a flat picture, while CT takes a section picture. the scope of CT examination is much larger than that of X-ray, not only can it examine the bones, but also some substantial organs, such as the liver, kidneys, brain, etc. MRI utilizes the power of a powerful magnetic resonance imaging (MRI) system to examine the human body. MRI uses a powerful magnetic field to vibrate the water in the body, using the difference in vibration of the water in different tissues to form an image, which can be used to distinguish between normal and diseased tissues. This is why MRI is also jokingly referred to as a “shaking test”. MRI can be performed at any angle and is radiation-free. MRI soft tissues are more clearly structured. It also shows better anatomy and lesions in the cranium, crest and medulla oblongata than CT. Ultrasound is the use of ultrasound to penetrate the human body, sound waves encountered in human tissues will produce reflected waves, the reflected echo is ultrasound image. ultrasound is known for its low intensity, high frequency, no damage to the human body, no pain, and a variety of display methods. In particular, it is unique in the detection of human soft tissue and the observation of blood flow in blood vessels. In modern medical imaging, ultrasound, CT, X-ray and MRI go hand in hand and complement each other. These several checkup programs can not completely replace each other, the specific need to take which way to check, according to the physical condition, listen to the doctor’s advice to determine.