Unit 1
When were XRs discovered?
Nov. 8 1895
A combination of rows and columns of small pixels are called what?
Matrix
What primary factor is directly proportional to the quantity of XRs produced?
mAs
What do you lose control of when using AEC?
Time (seconds)
What uses a continuous beam of XRs to create images of movement of anatomy?
Fluoroscopy
What is the relationship between wavelength and frequency?
Inverse
More shades of grey digitized & displayed is called what?
Contrast Resolution
What technical factor alters the amount and penetrating ability of the beam?
kVp
What shows the exact amount of mAs used for exposure during AEC?
mAs readout
What is the first step in the II tube?
Input Phosphor; XRs absorbed & changes to light.
What % of the XR beam will be characteristic interactions with a 90kVp?
15%
What is the distance from the center of one pixel to the center of the next?
Pitch
What does changing OID affect on an image?
Distortion, Spatial Resolution, Contrast & IR Exposure
What is used to prevent excessive exposure to patients?
Back Up Time
150% of expected mAs
What is the equation for brightness gain?
minification gain X flux gain
2.5mm
What is the efficiency of the IRs ability to convert XR exposure to a quality image?
Detective Quantum Efficiency (DQE)
The intensity of the XR beam is inversely proportional to the square of the distance from the source- what is this called?
Inverse Square Law
With a variable kVp technique chart, you change the kVp for every X cm increase in thickness?
1cm.
What reduces overall patient dose and image noise by averaging multiple image frames?
Frame Averaging
What electron is removed during the Compton effect?
Outer shell electron
What is the graphic representation of the range & # of pixel values?
Histogram
What type of grid cutoff can happen with both focused and parallel grids?
Off-level cutoff
What type of technique chart has a standardized subject contrast?
Fixed kVp
What type of mA is used in digital fluoro? Why?
High mA- shorter time w/ a pulsed beam