RAD 354 Chapt. 8 X-ray emission X-ray output in AIR is measured in ROENTGENS and refers to x-ray QUANTITY 1 R = 2.58 X 10-4 C/kg

4 Factors affect the QUANTITY of RADIATION: mAs, kVp, distance & filtration mAs – DIRECTLY proportional to the x-ray quantity kVp – x-ray quantity varies proportional to the SQUARE of the RATIO of the kVp Distance – Inverse square law Filtration – Absorbs/Attenuates the LOW energy LONG wavelength photons – INCREASES average hardness of the beam

X-ray QUALITY = Penetrability INCREASED hardness = INCREASED penetration and DECREASED wavelength Measured via HALF VALUE LAYER (HVL = BEST measure of x-ray QUALITY) Penetrometer/step wedge Filtration – used to harden the beam and absorb the “useless, long wave photons” Inherent (.5 mm al) Added = 2 mm al (70-80 kVp)

“Special” Filters Trough – for CXR’s “Bow Tie” – for some generations of CT Wedge – for use with an AP foot, etc. Conic – for digital fluoro Don’t reduce patient dose, but improve the image