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RT 20 Digital
physics digital test
| Question | Answer |
|---|---|
| _____is the ability to image two separate objects visually detect one from the other | resolution |
| the science of______ is the study of the response of the human eye to light | photometry |
| radiographic_____ is the random fluctuation of the optical density of the radiograph | Noise |
| in Digital radiography, the latent image is formed on | the radiation detector |
| switching from screen film imaging to computer radiography can____ patient dose | reduce |
| what is the basic photometric unit | lumen |
| spatial resolution improves with decreased _____blur | geometric, screen, and motion |
| in digital radiograghy the brightness of the image is determined by | pixel values |
| computed radiograghy screens respond to radiation with | photostimuable luminescence |
| scanned projected radiography was developed as a complement to | computerized tomography |
| preprocessing the digital image is done | automatically |
| postprocessing the digital image is done | manually |
| the slope of the ____ portion of the charactaristic curve shows the film contrast | straight line |
| computed radiograghy imaging produces____ gray levels | 10,000 |
| in digital radiography, spatial resolution is improved with increased______ | matrix size |
| during preprocessing, the digital output of the image receptor may need to be manipulated to correct | dead pixels |
| an image receptor with _____ can be used over a greater range of exposeures | wide latitude |
| the computed radiographt cassette is called | an imaging plate |
| computed radiography uses_____ for latent image formation | photostimulable phosphor |
| is done during preprocessing to correct for an irregular pattern of the image | flatfielding |
| the primary geometric factors affecting image quality are | magnification, distortion, and focal spot blur |
| the photostimuable phosphor screen is handled in a | reader |
| conventional x ray tubes and cassettes are used with_____ radiography systems | computed |
| what is the formula for the magnification factor | MF=SID/SOD |
| backscatter radiation artifacts can occur more readily in digital imaging because of the | highly sensitive receptors |
| four steps of creating an image with computed rediography are | metastable state, stimulate, read, and erase |
| in digital, each matrix pixel represents | atomic number and mass density |
| the best way to minimize magnification is to use | long SID and small OID |
| europium is the_____ of the photostimuable phosphor | activator |
| a graph of the frequency of occurances versus digital value intervals is called______ | histogram |
| spatial frequency is used to describe the quality of spatial resolution in terms of | line pairs |
| focal spot blur can be reduced by usin | a smaller focal spot |
| t/f....the digital imaging plate can sit for sometime after the erase cycle | false |
| in digital imaging, spatial resolution is ultimately limited by | pixel size |
| subject contrast is affected by | patient thickness |
| each anatomical part has an image histogram with____shape | characteristic |
| the human visual system can distinguish______shades of gray | 30 |
| histogram selection is done____ | by the radiographer before each exam |
| computed radiography and screen film imaging both have an____ | latent image |
| the number of gray shades that an imaging system can reproduce is called its | dynamic range |
| between the abdomen, chest, skull, and pelvis, which part has the highest subject contrast | chest |
| the principal source of noise in computed radiography is | scatter radiation |
| the_______ digital imaging system uses the highet dynamic range | mammography |
| radiographic image quality is improved when the______is increased | source image distance |
| creating distinctly collimated margins on all 4 sides of the DR image is important in preventing_______ errors | histogram analysis |
| image detail is also called | spatial resolution |
| patient thickness affects image quality by affecting_______ | magnification, focal spot blur, and radiographic contrast |
| the computed radiograghy image has | wide exposure latitude and improved contrast resolution. |
| with digital imaging patient dose can be reduced by using higher_____technique | kVp |
| the technologist primarily controls radiogrphic contrast by varying the | Kilovoltage |
| a ghost image can occur in digital imaging because of | an image is not fully erased |
| the software correction that equalizes the response of each pixel to uniform exposure is | flatfielding |
| DQE is an acronym for | Dective Quantum Exposure |
| Improves as screen blur decreases, motion blur decreases, and geometric blur decreases | Spatial resolution |
| the use of high mass, low kvp, and slower image receptors reduces | quantum mottle |
| latitude and contrast are_______ proportional | inversly |
| unequal maginification of different portions of the same object is callled | Distortion |
| the most important factor for determining spatial resolution | focal spot size |
| 3 thing to reduce motion blur | Decrease Exposure time, give instructions, use immobilizers |
| In the CR reader the latent image is made visible bt realeasing the_____________with stimulating laser light beam | metastable electrons |
| spatial resolution in DR is | pixel limited |
| IP | Imaging plate |
| PD | photodiode |
| PMT | Photomultiplier tube |
| PSL | photostimuable luminescence |
| PSP | Photostimulable phosphor |
| SP | storage phosphor |
| SPS | Storage phosphor screen. |
| as matrix size increases the pixel size_____ and the resolution______ | decreases, increases. |
| _____are the light detectors of choice for CR | photodiodes |
| the first of the sequence of events that result in an xray induced image forming signal | Expose |
| results from the interaction of an infrared laser beam with photostimulable phosper | stimulate |
| the light signal emitted after stimulation is detected and measured | Read |
| before reuse, an residual electrons are moved to ground state by an intense light | Erase |
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