CT is a fixed layer-by-layer scan． It's like sectioning and analyzing. Like a hundred pieces of A4 paper together, each on a different word, scanning is the paper does not move the machine to move layer after layer of scanning to synthesize an internal structure of the graphic to know what is written on each piece of paper. 3D printing is to do so. Layer by layer, the final copy of the internal structure of the final completion of the print scanning and printing is the same thing imaging and printing methods. MRI is dynamic, which is what we usually see when we take an X-ray, and CT is also static layer by layer.
Through the nuclear magnetic can see the dynamic internal state. For example, the blood circulation of the flow of these conditions, in the body surface with the naked eye we can not see the blood flow in the body. Through the X-ray and layer-by-layer fixed scanning can be seen in the body but is fixed. Can not see the dynamic cycle of change in the state, and nuclear magnetic can see the inner can also see the dynamic state, equivalent to countless fixed X-ray to see the synthesis of the flow of movement after the animation of a state. The still picture into a dynamic flow of the picture of a state.
These are commonly used examination equipment, each with its own advantages, such as ultrasound is the most simple, but also cheap. CT is very sensitive to density, to see the advantages of calcification, but also very quickly, but only the radiation of X-rays, need to pay attention to. MRI, on the other hand, picks up the richest signals and, for most areas, is the best for clarity.
B ultrasound is a sonar feedback imaging with ultrasound. Instead of rays, sound waves are used, and all three are designed to see places in the body that are invisible to the naked eye． The method is to use different substances and principles, such as ultrasound imaging. Magnetic dynamic imaging, CT layer-by-layer imaging of these scientific methods. The solution to the human five senses can not reach the state.
The human eye are extended places. Because each has its own advantages and disadvantages, so the application is different. For example, ultrasound can be used to see the fetus. Other damage to the big do not use, but also but out of metal objects or there will be an electromagnetic reaction will be hot, such as microwave ovens, but also movement, such as electromagnetic artillery. So before checking the state should be clear check the purpose and reason of the state.