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Fixed spatial resolution characteristic of direct digital systems is determined by
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What is foreshortening?
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RADT465 operation
operation, QA, acquisition, and evaulation
| Question | Answer |
|---|---|
| Fixed spatial resolution characteristic of direct digital systems is determined by | TFT DEL size |
| What is foreshortening? | an object is placed at an angle on the detector (object not flat) |
| grid absorption of useful beam | grid cutoff |
| what is bit depth | number of bits per pixel which has an effect on the gray scale |
| a technique of 85kV and 10mAs with no grid. what mAs is needed with a 8:1 grid | 40 mAs |
| what gird ratio is similar to the air gap technique | 6:1 ratio |
| formula for magnification | SID/SOD |
| formula for heat units | # of exposures*kVp*mA*seconds*generator |
| multiplier for a three phase 6 pulse generator | 1.35 |
| multiplier for three phase 12 pulse | 1.41 |
| find the new intensity for an AP chest x-ray at 55 inches, with an intensity of 50mR. The new distance is 72 inches. | 29.2 |
| old mAs is 10 with a 6:1 grid. find new mAs with a 16:1 grid | 20 mAs |
| purpose of fuses on the xray circuit | safety to protect equipment. will stop exposure if there is too much voltage |
| what is an autotransformer | single coil transformer, operates on self induction, minor adjustments in kVp |
| anode is positive or negative | positive |
| cathode is positive or negative | negative |
| kvp is quality or quantity | quantity |
| mAs is quality or quantity | quality |
| what type of histogram is used for extremities | type 1 |
| what histogram is used for KUB's | type 2 |
| what histrogram type is used for contrasted exams | type 3 |
| primary coil of the high voltage transformer receives what current | AC |
| energy needed to eject k-shell electrons from a tungsten atom | 70 kVp |
| three causes for tube failure | 1. vaporized tungsten 2. pitted anode 3. cracked anode |
| the x-ray tube is a | vaccuum |
| what is needed to find the total filtration | additive and inherent filtration |
| less than 1% of the energy from electrons are turned into this | x-rays |
| what relationship does the line focus principle show | actual and effective focal spot |
| characteristics of tungsten include | 1. heat dissipation 2. high melting point 3. high atomic number |
| what is thermionic emission | electron cloud within the x-ray tube is the product |
| what is aec used for | ensure reproducible radiographs regardless of tissue differences |
| circuit device that permits electrons to flow in one direction | resistors |
| what voltage must the primary side of the x-ray circuit be at | 220 volts |
| what percent of voltage ripple happens in a 3 phase 12 pulse have | 4% |
| how much voltage ripple occurs in a high frequency generator | less than 1% |
| 3 parts of the x-ray circuit | primary, secondary, and filament circuit |
| what is located between the secondary coil of the high voltage transformer and the x-ray tube | filament circuit |
| how is pixel size determined | dividing FOV by matrix |
| interrogation time is | the time needed for the x-ray tube to turn off |
| what are the two types of AEC | ionizing chamber and phototimer |
| what does bit depth identify | gray scale values |
| what effects spatial resolution | OID, SID, focal spot size, and motion |
| magification is effected by | OID and SID |
| elongation and foreshortening are effected by | tube alignment of x-ray tube, anatomic part, and IR |
| visibility factors are | brightness, contrast, and noise |
| what describes DQE | percentage of detected incoming x-ray photons |
| terms used to describe distortion | magnification, elongation, and foreshortening |
| percent of incoming x-ray photons that are identified and absorbed by the detector describes | DQE |
| focal spot blur is greatest | toward the cathode end of the x-ray beam |
| true or false: SID has no effect on contrast | true |
Created by:
smshelton2
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