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RAD170 Chapter 40
Fluoro
Question | Answer |
---|---|
Where is the fluoro tube? The image intensifier? | tube under table, image intensifier above |
What are the components of the image intensifier? | input phosphor, photocathode, electrostatic focusing lenses, anode, output phosphor |
What is the input phosphor made of? | cesium iodide crystals |
What does the input phosphor do? | converts 1 x-ray photon to 300 light photons |
What is the photocathode made of? What is the charge? | cesium & antimony; negative |
What does the photocathode do? | converts 1 light photon to 1000 photoelectrons |
What are the charge & voltage of the electrostatic focusing lenses? | negative, 25-35 kVP |
What do the electrostatic focusing lenses do? | focus photoelectrons and accelerate them towards the anode |
What happens at the focal point? | the image is reversed |
What does the anode do? How? | attracts photoelectrons because of positive charge |
What is the output phosphor made of? | zinc cadmium sulfide |
What does the output phosphor do? | converts 1 photoelectron to 3000 light photons |
What is flux gain? How is it calculated? | increased brightness from photoelectron acceleration # of output photons/# of input photons |
What is minification gain? How is it calculated? | increased brightness from conentrating photons (input phosphor diameter)^2/(output phosphor diameter)^2 |
How do you calculate total brightness gain? | flux gain x minification gain |
What is ABC? | Automatic Brightness Control - maintains image brightness by adjusting technique automatically |
What are the 2 types of video camera tubes? What is their purpose? | vidicon & Plumbicon; convert light photons to electric signal for display on monitor |
What is a CCD? | charge-coupled device - semiconductor that stores the charge from light photons |