x-rays interaction with matter

of the 5 ways x-rays interact with tissue, which two are important in Radiology?

Compton scatter and photoelectric effect

What is more important to use than compton scatter and photoelectric effect?

The x-rays transmitted through the body without interacting, puts a dot on the IR

Differential absorption

the difference between x-rays absorbed photoelectrically in the patient and those transmitted to the IR

What is one big factor in differential absorption?

Greatly depends on the atomic number of tissues, the higher the atomic number the higher probability absorption will happen

Radiopaque structures

do not reach the IR, represent anatomic structures with high x-ray absorption characteristic like high mass density or high atomic number

Radiolucent structures

x-rays that penetrate the body and are transmitted to the image receptor with no interaction (produces dark areas of an x-ray like air in lungs)

to image small differences in soft tissues, one must…

use low kVp to get maximum differential absorption (hence why KUB requires a low kVp, only need to image tissue and organs, not bones)

Two important factors in an x-ray image

x-ray emission spectrum and mass density of patient tissues

absorption

all or none condition for x-ray interaction (photoelectric)

Attenuation

reduction in the number of x-rays remaining in an x-ray beam after penetration through a given thickness of tissues