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Physics 2 Unit 4
Fluro
| Question | Answer |
|---|---|
| Name of the first image intensification screen | Patterson CB2 |
| Patterson CB2 screens were composed of: | zinc cadmium sulfide |
| Patterson CB2 screens emitted what kind of light? | low yellowish/green light |
| Reasons for improving the image intensification: | low bightness levels of the image low contrast of image only view one person at a time high radiation exposure to the PT dependence of rod vision work in total darkness |
| Light enters through which part of the eye? | lens |
| -membrane lining the inside surface of the eye | retina |
| two types of cells contained in the retina | rods, cones |
| Cones are used for what kind of vision? | day vision |
| rods are used for what kind of vision? | night vision |
| - ablility to discriminate small images | visual acuity |
| Cones discriminate btwn contrast levels as low as | 2% |
| - an electronic device which converts instantaneously, in several steps, an xray image pattern into a corresponding visible light pattern of significantly higher energy per sq cm of viewing screen | image intensification |
| Input screen takes _____ and emits _____ | xray photons ; light photons |
| What composes an input screen? | cesium iodide |
| Photocathode takes ____ and emits ____ | light photons ( from input) ; electrons |
| What is considered the most ineffecient part of the image intensifier unit? | the photocathe bc it takes alot of light photons to emit an electron |
| Output phosphor converts ____ to _____ | electrons ; visible light image |
| What surronds the output phosphor? | anode |
| What is the purpose of the electrostatic lens? | helps focus the electrons onto the output phosphor |
| Increase the kinetic energy = _____ image | brighter |
| How does image intensify? | electronic intensification, minification |
| - the term given to the intensity of light given off at the output phosphor in relation to the light given off by a Patterson CB-2 | image amplifier gain |
| - the measurement based on the comparison of light given off at the output phosphor in relation with the light given off by the input phosphor | brightness gain |
| - the random fluctuation of brightness over a given area caused by the number of light photons available at any given instant of time for that area | scintillation |
| - the ability of an amplifier to differentiate very small objects | resolution |
| - consists of one opaque bar and one equally wide opening on a test pattern | line pairs |
| - when electrons leave the photo emissive layer of the input phosphor and get pulled away from their path by outside magnetic forces | image rotation |
| - a metallic ring constructed of an alloy that has the same temp coeefficient as that of the glass envelope and is used as a cathode connection / helps keep the glass from breaking | covar ring |
| - the ability to differentiate borders | contrast |
| - the relationship btwn contrast and resolution | contrast sensitivity |
| - refers to focusing of the electrons leaving the photocathode | focusing |
| - photoelectrons from the photocathode meet in the center and ionize some gas molecules which causes an area on the output phosphor to be lacking electrons and shows up as bright spots | gas spots |
| - instruments used to remove the gas spots | gettering devices |
| - loss of light at the periphery of the image | vignitting |
| The smaller the field of view ( FOV) , the more ______ the image becomes | magnified |
| Increasing magnification, will have what effect on pt dose? | increases |
| - varies the exposure factors according to the changes in the part examined | Automatic brightness control |
| - varies the electronic signal as needed | automatic gain control |
| - compensates for part thickness changes as the pt is moved during the exam | automatic exposure control |
| Where is the brightness control knob located? | on the fluoro tower |
| kV rec: gallbladder | 65-75 |
| kV rec: nephrostogram | 70-80 |
| kV rec: myelogram | 70-80 |
| kV rec: BE/Air-contrast | 80-90 |
| kV rec: Upper GI | 100-110 |
| kV rec: Small Bowel | 110-120 |
| kV rec: Barium Enema | 110-120 |
| What should the fluoro timer be set for? | 5 min |
| Brightness is usually adjusted so that the darkest area on the monitor is ______ | black |
| When contrast is increased at the TV monitor, the amt of visible background noise on the monitor ______. | increases |
| Adjust _____ first, then _____ | contrast ; brightness |
| To reduce unwanted magnification, the fluoro tower should be? | kept as close to the pt as possible |
| What is the source-to-table distance | 38 cm on stationary 30 cm on mobile |
| Increasing the distance _____ pt dose | decreases |
| Filtration must be at least ____ mm AL | 2.5 |
| Bucky slot cover must be at least ____ Pb equ. | 0.25 |
| protective curtain must be at least ____pB equ. and must measure _______ cm | 0.25 ; 45 x 45 |
| At the table top, xray intensity should not exceed....... | 2.1 R / min for each mA operation at 80 kVp |
| What is the max intensity during fluoro? | 10 R / min |
| For every milliampere of fluoroscopic tech, one can assume a tabletop intensity of | 2 rad / min |
| What is the most commonly used camera tubes? | vidicon |
| in a TV camera, what serves as the cathode? | electron gun |
| in a TV camera, what serves as the anode? | target assembly |
| an electron beam forms a light image on the TV screen by producing a .... | raster pattern |
| the electron beam starts in the upper-left corner of the screen and moves to the upper right corner to produce | active trace |
| the electron beam is then blanked and returns to the left side of the screen.... | horizontal retrace |
| another term for turned off | blanked |
| Raster pattern, active trace, horizontal retrace all form the.... | television field |
| the elctron beam is turned off and forms a ______ at the top of the screen | vertical retrace |
| what is the most common used line system> | 525 |
| What is the weakest link in the image intensified fluoro.... | tv monitor |
Created by:
erikasmith28
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