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X-RAY EMISSION SPECTRUM. X-RAY PRODUCTION. BREMSTRAHLUNG RADIATION CHARACTERISTIC RADIATION. BREMS. BREMS EMISSION-CONTINUOUS. Characteristic Radiation. CHARACTERISTIC EMISSION- LESS POLYENERGETIC. X-RAY EMISSION SPECTRUM. BREMS. INTENSITY. X-RAY ENERGY. X-RAY EMISSION SPECTRUM.
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X-RAY PRODUCTION • BREMSTRAHLUNG RADIATION • CHARACTERISTIC RADIATION
X-RAY EMISSION SPECTRUM BREMS INTENSITY X-RAY ENERGY
X-RAY EMISSION SPECTRUM L-CHARACTERISTIC K-CHARACTERISTIC BREMS INTENSITY X-RAY ENERGY
X-RAY EMISSION SPECTRUM CHARACTERISTIC BREMS
MAXIMUM ENERGY OF AN X-RAY IN THE BEAM = kVp OF OPERATION kVpeak
GREATEST # OF PHOTONS IS EMITTED WITH ENERGY: APPROX. 1/3 OF MAX PHOTON ENERGY
FOUR PRINCIPAL FACTORS INFLUENCING THE SHAPE OF AN X-RAY EMISSION SPECTRUM: • ELCTRONS TRAVELING FROM CATHODE TO ANODE HAVE DIFFERENT ENERGIES– NOT JUST PEAK ENERGY • THE TARGETIS RELATIVELY THICK– CAUSING MULTIPLE INTERACTIONS. • LOW ENERGY X-RAYS ARE MORE LIKELY ABSORBED IN THE TARGET • EXTERNAL FILTRATION REMOVES LOW ENERGY PHOTONS
FACTORS AFFECTING THE X-RAY EMISSION SPECTRUM • TUBE CURRENT • TUBE VOLTAGE • ADDED FILTRATION • TARGET MATERIAL • VOLTAGE WAVEFORM
CURRENT CHANGE INTENSITY AVG. ENERGY – NO CHANGE CURRENT 2 * mA = 2 * number of photons 4 * mA = 4 * number of photons
Tube voltage (kVp) CHANGE INTENSITY AVG. ENERGY – kVp 15% INCREASE OF KVP = 2 * mAs
FILTRATION CHANGE 2.5 mm 4 mm
FILTRATION CHANGE INTENSITY AVG. ENERGY – FILTRATION
TARGET MATERIAL CHANGE TUNGSTEN MOLYBDENUM 70
74 W 57981.77(14) 59318.847(50) 75 Re 59718.57(43) 61141.00(89) 76 Os 61487.27(90) 63001.07(95) 77 Ir 63287.29(96) 64896.2(10) 78 Pt 65123.3(20) 66832.9(21) 79 Au 66990.73(22) 68804.50(18) 80 Hg 68895.1(17) 70819.5(18) 81 Tl 70832.5(12) 72872.5(13) 82 Pb 72805.42(24) 74970.11(17) 83 Bi-209 74816.21(92) 77109.2(22) K-CHARACTERISTIC ENERGY FOR DIFFERENT TARGETS
TARGET CHANGE INTENSITY AVG. ENERGY CHARACTERISTIC RADIATION CHANGE TARGET MATERIAL Z #
VOLTAGE-WAVEFORM CHANGE 3-PHASE 1-PHASE
VOLTAGE WAVEFORM CHANGE INTENSITY AVG. ENERGY VOLTAGE WAVEFORM
PATIENT DOSE SINGLE PHASE > THREE PHASE