POI P3

24問 • 1年前

通報

問題一覧

exposure without screens over exposure with screens

Intensifying Factors

amount of light emitted by screen for given amount of exposure

Screen Speed

2 Types of Screen Speed

2 Types of Screen Speed * FAST - creates an increased amount of light compared with slow * SLOW

should be used to reduce patient exposure

high kVp & lower mAs

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

kVp

needed to achieve a desired exposure to the IR

Less Radiation

2 principal factors that affect amount of scattered radiation KI

Kilovoltage, Irradiated Materials

scattering of incident photons onto an outer shell electron of atom

Compton Scattering

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

Photoelectric Absorption

photon energy is converted to positron and electron

Pair Production

transfers negligible energy to atom

Coherent Scattering

related to contributions of scattered photons at calibration

Correction Factor in Radiology

ratio of true dose rate to instrument’s response rate

Correction Factor in Radiation

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

Pediatric patients

eliminate possibility of using automatic exposure control (AEC)

Fast exposure time

higher risk for children than adults

Thyroid & Skin Cancer

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

decrease kVp by 15% to compensate

When lacking bone density

2 FACTORS THAT CAN CAUSE MAGNIFICATION DP

- distance from plate - printing or monitoring radiographs

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

25.4mm 0.3mm

can be produced with materials that attenuate x-rays

Casts/Splints

made of fiberglass or plaster

Casts

MATERIALS THAT REQUIRE NO INCREASE IN EXPOSURE FA

Fiberglass Air

MATERIALS THAT REQUIRE AN INCREASE IN EXPOSURE WASP

Wood Aluminum Solid Plastic Splints Plaster

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