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physic U4 fluro
physic U4
| Question | Answer |
|---|---|
| Who invented image intensification and when? | Thomas Edison ; 1896 |
| What was the first image intensification screen called? | Patterson CB2 screen |
| Early fluoroscopy required what for the eyes? What eyes could be worn? | Dark Adapt ion; Red goggles |
| The patterson CB2 were composed of what? | zinc cadmium sulfide |
| What did the patterson CB2 emitt? | yellowish/green light which is a very low light |
| When were advances made to image intensification and why? | in 1960s to improve the brightness levels |
| What things are read for improvement in image intensification? | low bightness levels, low contrast(of image) , image could only be viewed by one patient at a time, high radiation exposure to the patient, dependence on rod vision and work in total darkness |
| The light is reflected from an object and enters through what? | lens at the front of the eyes |
| Where is the light focused in the eye? | retina |
| What is the membrane lininig the inside surface of the eye? | retina |
| What are the two types of cells that the retina contains? | rods and cones |
| These are concentrated in a small spot in the center of the eye and are sensitive to light at ordinary brightness(used for daylight) | cones |
| These are cells distributed throughout the retina and are used at low brightness levels(darkness) | rods |
| This is the ability to discriminate small images? | visual acuity |
| Cones can descriminate between contrast levels as low as what? | 2% |
| rods can only discriminate between contrast levels that are at at least what? | 50% |
| How much time for darkness is needed to adapt for conventional fluoroscopy is required? | 20-30mins |
| What is an electronic device that converts instantaneously, in several steps, an x-ray image pattern into a cooresponding visible light pattern of significantly higher energy per square cm i=of viewing system | image intensification |
| radiation first passes through what at the front of the intensifier? | an aluminium dish |
| Radiation cause what to emitt when striking the input screen/phosphor? | light photons |
| One x-ray photon will produce how many light photons | 32,000 |
| What is the input screen/phosphor composed of | cesium iodide |
| the photocathode is seperated from the input phosphor by what | a thin sheet of glass |
| When light photons hit the photocathode what are emitted?This is called what because it takes a lot of light photons to emit an electron? | electrons; the most inefficient part of the unit |
| What is the photocathode composed of? | antimony potassium and sodium cesium |
| This is surrounded by an anode | output screen/phosphor |
| What does the output screen/phospher convert elctrons (electrostatic latent image into? | visible light image of much greater brightness |
| What is the output screen/phosphor composed of? | zinc sulfide |
| Where are the electrostatic lens/grids placed | between the photocathode(-) and the output phosphor(+) |
| What does the electrostatic lens/grids do? | Help to focus the electrons(electrostatic image) onto the output phosphor |
| A potential difference of___kVp between the - and + to increase what? | 25; kinetic energy of the electrons |
| what does all of these intensify? | electronic intensification and minification |
| The giving of the electronos kinetic energy is called? | electronic intensification |
| What does electronic intensification do? | increases the kinetic energy between the photcathode and the output phosphor will increase the brightness approximately 50 times |
| the light photons are forced into a smaller area on the output phosphor as compared to the input phosphor is called? | minification |
| give the order in which the energy is transfered in the input screen/phosphor? | radiation energy->light photon energy->electrons(electrostatic latent image->visible light image |
| give the order in which the energy is transferred in the output screen/phosphor | x-ray->light->electrons->light->electric signal->light |
| Electronic intensification will be responsible for about______ of the increase in brightness and minification about____ of the increase in brightness for and approximate increase of brightness of about_____ | 50 times: 80 times; and 400 times |
| This is the term given to the intensity of light at the output phosphor in relation to the light given off by a Patterson CB2 screen | Image Amplifier Gain |
| What is image amplifier controlled by | Electronic intensification (minification) |
| This is the measurement based on the comparision of light given off at the output phosphor in relation with light given off by the input phosphor | Brightness gain |
| This is the radom fluctuation of brightness over a given are caused by the number of light photons available at any given instant of time for that area | scintinllation |
| This is the ability of an amplifier to differentiate very small objects(detail) | resolution |
| What is resolution measure in | lines per inch using the line bar test tool |
| What are the factors that affect resolution? | geometric blurring due to focal spot size; geometric blurring due to phosphor graininess, and scintillation/quanyum noise caused by too low mA |
| One pair consists of one opaque bar and one equally wide opening on a test is called | line pairs |
| Line pairs are expressed in | per inch or millimeter |
| WThis is when electrons leave the photo emissive layer of the input phosphor and get pulled away from their path by outside magnetic forces | Image rotation |
| Sun spots can cause as much as ___ rotation | 14 degrees |
| This is a metallic ring constructed of an alloy that has the same tempature coefficient as that of the glass envelope and is used as a cathode connection | covar ring |
| The covar ring helps the glass from_____ | breaking |
| This is the ability to differentiate borders | contrast |
| This is the relationship between contrast and resolution | Contrast sensitivity |
| This refers to focusing the elctrons leaving the photocathode | Focusing |
| This is when photoelectrons from the photocathode meet in the center and ionize some gas molecules which causes an area on the output phosphor to be lackin electrons and shows up as bright spots | gas spots |
| These are instruments used to remove the gas spots and is done automatically | gettering devices |
| This is when brightness fall off; loss of light at the periphery of the image; pin cushion effect; and is due to the curvature of the photocathode | vignitting |
| Most intensifiers come from either 2 or 3 what | Fields of view(areas examined) |
| This is actually changing the size of the out put phosphor | Multifield Image intensifier |
| What are the most common types of multifiled image intensifiers | Dual mode at 25cm/17/cm and triple mode 25cm/17cm/12cm |
| When a smaller FOV is selected what happens | a higher voltage is placed on the electrostatic grid |
| If you increase the voltage you do what to the FOV | decrease it |
| The smaller the FOV is what happens to the image | the more magnified it is |
| Increasing the magnification does what to the patient | increases the dose |
| the magnification mode reduces the minification gain causing a | dimmer image/ to compensate for this the mA is automatically increased |
| The ABC varies the_____ accrouding to the changes in the part examined | exposure factors |
| Where is the detector(ABC) placed on the fluro tower | in the beam |
| AGC varies what | the electronic signal as needed |
| This compensates for part thickness changes as the patient is moved during an exam | brightness control |
| Where is the brightness control knob located | on the fluoro tower which can be adjusted by the operator as needed |
| The fluromA is usually between | 4-6mA |
| kV for each gallbladder; nephrostogram; myelogram; BE/Air contrast; Upper GI; small bowel; Barium enema | 65-75;70-80;70-80;80-90;100-110;110-120;110-120 |
| What should the fluoroscpic timer be set at the begining of every procedure | 5 minutes |
| When contrast is___ at the TV monitor, the amount of____on the monitor will___ also | increased;visible background noise; increased |
| The contrast knob should be _____ until the background noise is visibke then___ slightly to reduce the____ | turned up;turned down; noise effect |
| The ___ should be adjusted first then____ | Contrast; brightness |
| To help reduce unwanted magnification what should you do? | the fluoro tower should be kept as close to the patient as possible |
| The brake should be what for the patients safety | in place for the patients safety during myelgrams |
| What is the source to table top distance for stationary unit; mobile unit | 38cm stationary; 30cm for mobile units |
| What is the equivalence for filtration | at least2.5mm AL |
| What must the exposure switch be | a dead mans switch |
| What is the equivalence for the bucky slot holder | .25mm Pb |
| What is the equivelance for the protective curtain | .25mm Pb 45x45cm |
| What is the intensity for a table top; for fluoroscopy | should never exceed 2.1R/min for each mA of operation at 80kVp;10R/min should never be exceeded |
| for every____ of fluoroscopic technique one can assume a tabletop intensity of______ | milliampere;2rad/min |
| The image intensifier assembly serves as a primary protective barrier and must be at least____ | 2mm Pb equivalent |
| What is the most commonly used TV camera | Vidicon |
| What is the second most commonly used TV camera | Plumbicons |
| What are the components of a television camera and what do they serve as | Electron gun-cathode; target assembly-anode; electrostatic grids |
| What are the advantages and diadvantages of a fiber optic | A-small size,easly manipulated and can withstand rough handling D- can not accommodate other imaging devices and cassette loaded spot films asr necessary |
| this has a beam splitting mirror which reflects a predominate percentage of the light in one direction for stimulataneous viewing/recording | lens coupling |
| this accepts the light for the output phosphor and alignment of the lens is the most critical | objective lens |
| What are the methods of coupling of TV cameras | has a beam splitter and objective lens |
| What are the advantages and disadvantages to lens coupling | A-allows for multiple viewing systems D-large |
| An electron beam forms a light image on the TV screen by producing____ | raster pattern |
| The electron beam starts in the upper-left corner of the screen and moves to the upper right cornor to produce an______ | Active trace |
| The electron beam is blanked(turned off) and returns to the left side of the screen which is called | horizontal trace |
| The process continues all the way down the screen to form a____ | Television field |
| The electron beam is then turned off and forms a ______ up to the top of the screen | Verticle trace |
| The electron beam then forms another_______ with each active trace being formed between two adjacent active traces of the first field(____) | television field; interlace |
| Two interlaced field for what and each field has___ lines every____secs; this forms one_____ tv field every_____ sec; _____is teh most commonly used | one television frame; 262 lines;1/60;525 line;1/30; 525 line system |
| The television monitor is the____ link in the image intensified fluoroscopy | weakest |
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