Methods of Image Formation and Laws of Projection

Abstract

The most important property of X-rays, without which they could not be put to diagnostic use, is their ability to penetrate matter to a greater or lesser extent. All degrees of transmission are possible, ranging from complete transmission of the radiation to complete impenetrability. It is due to this penetrating power of X-rays that we are able to use them to gain a visual impression of the internal constitution of the human body, in as much as the parts of the body differ in the amount of radiation they absorb. The laws that govern the attenuation of X-rays in matter have already been discussed. Differences in degree of attenuation are thus obviously to be expected in the human body, owing to differences in the density and atomic composition of the various tissues as well as in the thickness of the layers which have to be passed through.