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diagnostic systems
| Question | Answer |
|---|---|
| what are the layers of the IP in CR | *backing *base *anti halo/reflective *phosphor *protective |
| what is the purpose of the backing | *mounted to the back of cassette *prevents handling artifacts *contains barcode *prevents static energy |
| what is the purpose of the base layer | support |
| what is the purpose of the anti halo/reflective layer | *prevents laser light from bouncing back and causing fog or noise *allows reflected light to be emitted to phosphor *anti-halo is blue *reflective is white |
| what is the purpose of the phosphor layer | *acquires latent image *site of f centers |
| what is the purpose of the protective layer | *tubeside *prevents handling artifacts *allows cleaning |
| what is S:N ratio | the ratio of useful informatin vs noise or unuseful information |
| what is contrast | density differences |
| what is the relationship between S:N ratio and contrast | direct |
| window level | controls brightness -direct relationship |
| window width | contrast(gray scale)(visibility of detail) -inverse relationship |
| what determines the maximum spatial resolution for a given sampling frequency by IRD | nyquest frequency |
| spatial resolution | the sharpness of structural edges recorded in the image |
| exposure latitude | range of exposures which produces optimal image with appropriate dose *since range is wider with digital radiography this can lead to dose creep |
| dynamic range | range of exposures that may be captured by a detector |
| bit depth | controls number of shades of gray that can be visualized -formula=2 to the nth(n=number of bits) |
| equalization | software function designed to even the brightness (density). light areas are made darker and dark areas lighter *good for tube placement in chest imaging |
| edge enhancement | *artificial increase in contrast at edge of structures *diamond view is the siemens term *also called high pass filtering(convolution) |
| smoothing | *software function to reduce the appearance of noise but causes loss of fine detail *also call low pass filtering(convolution) |
| stitching | *software that allows RT to place images together if too long for IR *scoliosis pt's *long bone measurement |
| what types of DR scintilators can we use today | *cesium iodide(indirect)(CCD) *godolinium oxysulfide(indirect)(CCD or TFT) |
| minimum response time | length of exposure required to produce an image |
| variable resistor(mA selector) | rheostat |
| measures electric potential(parallel circuit) | voltmeter |
| measures electric current(series circuit) | ammeter |
| transformer | increases or decreases voltage by fixed amount (AC only) |
| deadman switch | shuts off as let as you let off switch |
| anything that a radiographer will be touching is on the _____________ side of the circuit | primary(low voltage) |
| select mAs, unit starts at highest mA and shortest time. mA drops off during exposure with appropriate time changes. Used to get shortes time for mAs | falling load |
| kVp selector | autotransformer |
| conversion of AC to DC to apply to tube | rectification |
| where are rectifiers found | between secondary coil of step up transformer and tube so that current will flow in one direction from filament to anode |
Created by:
bigad1982
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