RADT 3000 Review for Quiz 3 PDF

Review for Quiz 3 Intensifying Screens Parts of the Intensifying Screen  Base-  Reflective Layer  Phosphor Layer  Protective Coat *_____33_____ % of photons that strike IR form _____99______% of the image. Types of Phosphors Light emitted  Gadolinium Oxysulfide (Rare earth)=fa...

Review for Quiz 3 Intensifying Screens Parts of the Intensifying Screen  Base-  Reflective Layer  Phosphor Layer  Protective Coat *_____33_____ % of photons that strike IR form _____99______% of the image. Types of Phosphors Light emitted  Gadolinium Oxysulfide (Rare earth)=fast speed screens and used in digital because  Lanthanum Oxybromide (Rare earth)= green fast  Zinc Sulphide = fast and yellow - green slow screen speed  Calcium Tungstate= blue violet slow screen speed Size of Phosphor and Phosphor Layer  How is size related to speed?  How is size related to resolution?  How is size related to patient dose?  How is size related to receptor exposure? Intensifying Screen Speed What happens when speed increases?  _______ Spatial resolution/detail  ____INCREASES___ Size of phosphor  ___THICKER____ Phosphor layer  ___INCREASE____ Intensification factor  ___INCREASE____ Conversion efficiency Characteristics of LARGE Phosphors  ___GREATER______ Absorption efficiency  ___GREATER______ Conversion efficiency  ___GREATER______ Emission efficiency  DIRECTLY RELATED  Terminology  Luminescence= EMISSION OF LIGHT  Fluorescence= INSTANANEOUS EMISSION OF LIGHT  Phosphorescence= DELYAED EMISSION OF LIGHT WHEN SOMETHING STOPS  Screen lag/After glow= NOT DESIRABLE, CONTINUES LIGHT FOR AN EXTENDED TIME  Quantum mottle= RANDOM DISTRIBUTION OF PHOSPHURS LIGHTING UP  Modulation Transfer Function (MTF) = MEASURES INFORMATION LOST BETWEEN PATIENT AND IR  Screen Speed When screen speed increases  __INCREASES____ Receptor exposure  __DECREASE____ mA OR  ___DECREASE___ time  ____DECREASE__ Patient dose  ____DECREASE__ Spatial resolution/detail Screen Care  Poor screen contact  Results- LESS DETAIL AND ITS BLURRY  Quantum mottle  ____INCREASE____ Speed = ___HIGHER CHANCE OF_____ Quantum mottle  ___DECREASE_____ mAs/TIME = ____INCRASE_____ Quantum mottle  ____INCREASE____ kV = ____INCRASE______ Quantum mottle Receptor Exposure/Density What happens? WHEN ALL INCREASE  mAs=INCREASE  kVp= INCREASE  Filtration= DECREASE  Collimation= DECREASE  Grids= DECREASES  Screens= INCREASES  Distance= DECREASE *Note: Receptor exposure and screen speed are __DIRECTLY____ proportional. *EI number ___INCREASE___ Contrast/Latitude What happens?  mAs= NO AFFECT  kVp= INCREASE  Wavelength= SHORTER  Filtration= DECREASE  Collimation= SMALL  Grids  Screens  Distance Patient Dose  mAs=INCREASE  kVp=  Wavelength=SHORTER  15% Rule=DECRASE MAS  Filtration= DECREASE SKIN DOSE  Collimation= DECREASE  Grids= INCREASE  Screens=DECREASE  Distance =DECREASE Spatial Resolution/Detail  mAs  kVp  Filtration  Collimation  Grids  Screens  Distance Problem What has the greatest receptor exposure? A. 50 mA 200 ms 60 kV 8:1 grid 200 speed screen B. 200 mA 125 ms 70 kV 6:1 grid 100 speed screen C. 150 mA 100 ms 60 kV 5:1 grid 100 speed screen D. 250 mA 60 ms 70 kV 12:1 grid 100 speed screen Problem 50 mA 100 mA 300 ms _____ ms 70 kV 60 kV 12:1 grid 8:1 grid 400 speed screen 100 speed screen 60” SID 40” SID