Scatter and grids Flashcards
what is scatter
the scatter of xray beams
what are the problems with scatter
they increase patient dose and degrade image quality
what are the two types of scatter
coherent and compton scatter
what is coherent
this is when an incoming photon interacts with an atom causing it to become excited.
the photon is then absorbed and re-emitted in a different direction
what is compton scatter
this is when an incoming photon interacts with an atoms outer electron and kcocks it out of its outer shell and the photon donates some energy to the electron and it goes of and gets involved in different interactions
the photon which has a decreased amount of energy after donation deflects in a different direction and this is the an gle of scatter
how would you limit scatter
you could collimate effectively to ensure you dont use a bigger surface area than needed as a larger field size would increase scatter
you could also lower the kvp
what is the function of a scatter grid
the scatter grid is used to remove scatter in order to enhance contrast and image quality
it does this by absorbing scatter
why must the mAs be increased when using a grid
it is done in order to compensate for the absorption of some of the xray beam
