What is the essential difference between CT and X-ray? Can CT replace X-ray?

Essential difference: X-ray plain film is an image of three-dimensional volume overlapping on two-dimensional plane, while CT is a tomographic image. The reason is that CT is tomography, reconstruction (iterative method, back projection method, etc. ) according to the attenuation law of X-rays after scanning the human body once. X-ray plain film is an image that directly outputs X-rays and falls on the detector after being attenuated by human body.

In the short term, because of the difference in price and dose, CT will not completely replace X-ray, but it is possible in the future. But at this stage, if the plain film is completely enough for diagnosis and the operation is simple, taking plain film is the first choice.

Now many hospitals no longer take plain films of sinuses and inner ears, but use CT. Five years ago, many hospitals also took these two positions with plain films.