2 Types of Screen Speed

MATERIALS THAT REQUIRE AN INCREASE IN EXPOSURE WASP

exposure without screens over exposure with screens

- technical challenge for radiographers because of small size, require lower kVp & mAs - requires technologist to choose fast exposure

- can increase beam penetration when high, - affects exposure to IR, - can cause larger potential difference when increased

needed to achieve a desired exposure to the IR

higher risk for children than adults

scattering of incident photons onto an outer shell electron of atom

decrease kVp by 15% to compensate

2 FACTORS THAT CAN CAUSE MAGNIFICATION DP

Exposure factors for adult skulls can be used for pedia patients _ years older

energy of incident photon is totally absorbed by inner shell electron which is ejected (Photoelectron) with kinetic energy

can be produced with materials that attenuate x-rays

2 principal factors that affect amount of scattered radiation KI

eliminate possibility of using automatic exposure control (AEC)

Steel balls ___mm, difference in size between center less than ___mm

related to contributions of scattered photons at calibration

ratio of true dose rate to instrument’s response rate

transfers negligible energy to atom

should be used to reduce patient exposure

photon energy is converted to positron and electron

amount of light emitted by screen for given amount of exposure

made of fiberglass or plaster

MATERIALS THAT REQUIRE NO INCREASE IN EXPOSURE FA