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X-RAY EMISSION SPECTRUM

X-RAY EMISSION SPECTRUM. X-RAY PRODUCTION. BREMSTRAHLUNG RADIATION CHARACTERISTIC RADIATION. BREMS. BREMS EMISSION-CONTINUOUS. CHARACTERISTIC EMISSION-DISCRETE (EACH). GREATEST # OF PHOTONS IS EMITTED WITH ENERGY:. APPROX. 1/3 OF MAX PHOTON ENERGY.

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X-RAY EMISSION SPECTRUM

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  1. X-RAY EMISSION SPECTRUM

  2. X-RAY PRODUCTION • BREMSTRAHLUNG RADIATION • CHARACTERISTIC RADIATION

  3. BREMS

  4. BREMS EMISSION-CONTINUOUS

  5. CHARACTERISTIC EMISSION-DISCRETE (EACH)

  6. GREATEST # OF PHOTONS IS EMITTED WITH ENERGY: APPROX. 1/3 OF MAX PHOTON ENERGY

  7. 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

  8. FACTORS AFFECTING THE X-RAY EMISSION SPECTRUM • TUBE CURRENT • TUBE VOLTAGE • ADDED FILTRATION • TARGET MATERIAL • VOLTAGE WAVEFORM

  9. CURRENT CHANGE INTENSITY ENERGY – NO CHANGE CURRENT 2 * mA = 2 * number of photons 4 * mA = 4 * number of photons

  10. mAs DOES NOT AFFECT • ENERGY OF THE X-RAYS • PENETRATING POWER OF THE X-RAY BEAM • SPEED OF THE X-RAY PHOTONS!!!!

  11. Why changing mA or time • Avoiding motion – mA time • Pediatric technique modification • Reducing noise - mAs MOTION NOISE

  12. Tube voltage (kVp) CHANGE INTENSITY - ENERGY– kVp 15% INCREASE OF KVP = 2 * mAs

  13. kVp AFFECTS: • ENERGY OF THE X-RAYS • PENETRATING POWER OF THE X-RAY BEAM • INTENSITY ( NUMBER) OF X-RAY PHOTONS • IT DOES NOT CHANGE THE SPEED OF THE X-RAY PHOTONS!!!!

  14. kVp IN CT • 80-140 • TOO LOW – NOISE (NOT ENOUGH PENETRATION OF THE PATIENT ) PHOTON STARVATION!!!!!

  15. FILTRATION CHANGE INTENSITY ENERGY – FILTRATION

  16. FILTRATION AFFECTS: • AVERAGE ENERGY OF THE X-RAY BEAM • PENETRATING POWER OF THE X-RAY BEAM • INTENSITY ( NUMBER) OF X-RAY PHOTONS • IT DOES NOT CHANGE THE SPEED OF THE X-RAY PHOTONS!!!!

  17. FILTRATION MATERIAL • ALUMINIUM ( SPECIAL FILTER IN CT) BOWTIE TO MAKE THE BEAM HARDER AND MORE MONOENERGETIC

  18. TARGET CHANGE INTENSITY ENERGY CHARACTERISTIC RADIATION CHANGE TARGET MATERIAL Z #

  19. TARGET MATERIAL COMPOSITION IN CT • TUNGSTEN + RHENIUM

  20. VOLTAGE WAVEFORM CHANGE INTENSITY ENERGY VOLTAGE WAVEFORM OPERATION ON 3-PHASE EQUIPMENT = 12% * SINGLE PHASE

  21. PATIENT DOSE SINGLE PHASE > THREE PHASE

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