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RAD 122 Unit 3 Test
| Question | Answer |
|---|---|
| Why does an underexposure and overexposure still yield images? | - wide dynamic range, - automatic rescaling, normalization (displays values of interest to specific lvls, produces imgs w/ consistent brightness over a wide exposure range) -LUT (displays img w/ appropriate contrast) |
| Wide range of exposure from as low as ___ mR up to ____ mR | .01 mR to 100 mR |
| ____ exposure to receptor produces most acceptable images(approx. 200 speed class) in s# | 1mR (0.001 R) |
| advantages of digital over film-screen are? | preprocessing (ability to manipulate img before display) post-processing (ability to manipulate img after display) |
| Carestream, Every change of ____ EI represents a change in actual exposure by a factor of? | 300 EI, by a factor of 2 |
| Agfa, center of scale is ___ LgM. below ___ is considered underexposed while above ____ is overexposed. | center at 2.2 LgM. below 1.9 is underexposed and above 2.5 is overexposed. |
| Inverse proportional scales. Uses S#. | Fuji and Konica |
| detector elements in an active matrix array stop functioning, which means that no data from that area are included in the final img. appear as white specks mimicing pathologies, can be fixed w/ flat fielding. rough handling can cause this damage | Dropped pixels |
| processing error that can happen when switching from fluoro to regular exam on FPD. The old latent image is still on IR. | image lag |
| wireless DR IR's suffers from ____ _____ from devices that draw lrg amt of electronic power or from cell phones, laptops, and the like. | Electronic interference |
| digital system uses a preprocessing manipulation known as _____, which is a software correction to equalize the response of each pixel to make the image more uniform. | flat fielding |
| corrects defects by giving an average of surrouding pixel to correct defective pixels | signal interpolation |
| corrects defects by neutralizing any residue charges | offset voltage |
| ranges of values/receptor exposure intensities that can be displayed by the digital detector / imaging system | dynamic range |
| ellimates signals outside collimated margins. if margins not detected, extreneous data not included histogram | automatic exposure field edge detection |
| uses shape of image signal distribution to determine relevant information within the exposure field and exposure indicator value | histogram analysis |
| mapping grayscale "values of interest" to achieve specific display levels. provides images that have uniform display brightness over wide exposure range | automatic rescaling |
| system needs to see a defined collimated border of a minimum of 3 sides. this type of error is called | collimation error |
| each detector element has a certain amount of _________ associated with it | electronic noise |
| caused by the collection element not sufficiently sending all data to the computer for processing, resulting in incomplete image formation. | incomplete charge transfer |
| exposure are taken in too rapid a sequence, resulting in not enough time for each previous exposure to transfer the entire signal, creating an artifact known as "ghosting" | electronic memory artifact |
| in lrg detector arrays, several amplifiers are used that can vary in gain from one to the next. to correct in gain btwen detector elements (tiling), a process known as flat fielding is used. | Uneven amplification |
| happens through the back of the cassette that can either create noise in the image or may create an image of the internal circuitry found in the back of the cassette | Back scatter |
| Gross overexposure is when the mAs is ____% over the # suppose to use. this creates a lost of contrast too many photons. | 400% |
| increase in window width will ____ contrast | increase contrast |
| changes to window level will cause a change in ____ | brightness |
| we have no control over which source type of radiation? | Natural and internal |
| this source of radiation is emitted by the sun and stars | cosmic radiation |
| this source of radiation comes from naturally occurring radioactive materials that are located throughout the earth's crust. | terrestrial radiation |
| this source of radiation refers to the small amts of radioactive minerals normally found in the body, ingested from the small amount present in food and inhaled as air-borne particles | internal radiation |
| CR image plates contain a ___ and will therefore "store" a charge produced by background radiation. | storage phosphor |
| normal background radiation is anywhere from ____uR/day to 80uR/day or _____ to 3.5 mSv per year but can be more than 50 mSv/yr | 40uR/day to 80uR/day, 1.5mSv to 3.5mSv |
| CR imaging plates unused for more than ___ hours should be erased | 48 hours |
| are constantly refreshed and do not require erasure between long period without use. They do not storage phosphor like CR | FPD |
| _____ radiation is more intense than background radiation. this should be controlled for optimum image quality. | scatter radiation |
| T/F lead strips is like a shield and cause a histogram analysis error. | True |
| T/F using a grid decreases the amount of scatter and decreases patient dose. | False a grid has no affect on patient dose |
| T/F does not matter how big a part is needed between multiple field exposures. | False. the larger the part, the more spaces needed between multiple-field exposures. collimated border is needed for proper histogram analysis |
| over exposure causes more or less scatter production? thus increasing unwanted _____ and change of improper _______ | more scatter, increasing unwanted receptor exposure and chance of improper exposure field detection |
| is a double set of grid lines caused by the placement of a grid cassette in a bucky. this artifact also can occur in CR in the range of 85 to 100 lines per inch is used, and the rid lines are parallel to the CR reader scan lines. | Moire effect or zebra pattern artifact |
| _______ = approximately 1/2 the sampling frequency | Nyquist frequency. avoid using grid frequencies near nyquist to avoid moire/alaising |
| can occur if not enough samples are taken (less than twice per cycle), and the rep of the orginal signal will not be accurate after computer processing. Also can cause moire pattern artifact | Aliasing |
| T/F the number of conversions in CR creates a loss of information | True |
| T/F no light is lost during the light-to-digital conversion bc of the spreading out of light photons | False |
| bc there is a small distance between the _____ surface and the _______ of the photomultiplier, some light spreads out there as well, resulting in loss of information. | phosphor plate surface and the photosensitive diode of the photomultiplier |
| T/F the longer the electrons are stored, the more energy they lose | True |
| T/F if enough energy was lost, some lower-energy electrons are not stimulated enough to escape and information is lost | True |
| When laser stimulates electrons, some lower-energy electrons escape the ____ layer | active |
| T/F Indirect and direct radiography lose more signal to light spread than conventional radiography. | False they lose less signal to light spread than conventional radiography |
| intro in 1942, eliminated the need for the tech to set mAs bc this determines the exposure time and therefore total mAs. Tech still has to set kVp and correct chamber and density | AEC |
| With AEC, the only way to increase or decrease receptor exposure is to change the ______ | density selection |
| With AEC, if the body part is not centered over the selected chanbers then the image | could be under/over exposed, receptor exposure will be affected resulting in a repeat |
| With AEC, receptor exposure is affected by | - centering of the part - detector selection - density control setting |
| one of two types of AEC, where it measures quantity of radiation coming out of patient | photo timer behind receptor |
| one of two types of AEC, where it terminates exposure when IR has received required intensity | ionizing chambers |
| XR exit patient and interacts w/ flourescent screen which en converts xr to light, light photons enter photocathode where they are converted to electrons w/ same intensity as photons that created them | photodiode akaphototimer, or photomultiplier tube |
| T/F in AEC using ionization chambers, no phototube is needed bc it is replaced by a parallel plate ion chamber btwen the patient and the IR. | True |
| is the shortest exposure time the system can produce. hence why we dont use AEC w/ small anatomy | Minimum response time |
| is the maximum length of time the exposure continues using an AEC. | backup timer occurs at 5-6 seconds or at 600 mAs |
| adjustments allow the radiographer to adjust the amount of preset radiation detection sensitivity | density control |
| The standard configuration of detectors is a triad of rectangular shaped demarcated lines on the tabletop over vertical bucky. | detector configuration |
| T/F the presence of orthopedic metal prothesis, which cause radiopaque artifacts can cause an underexposed image | false it causes an overexposed image |
| In digital imaging display, which is the weakest link | the monitor bc the room is worth millions vs a $50 dollar screen |
| total intensity from the source. measured in lumens | luminous flux |
| intensity of light incident on a surface. unit is 1 foot candle, or 1 lumen per sq/m | illuminance |
| 1 foot candle = | 10.8 lux |
| property of source of light measured in lumens or candela | luminance intensity |
| similar to luminance intensity / another measure of brightness. measured in candela per sq/m or nit | luminance |
| the study of light | photometry |
| measures light | photometer |
| Primary display monitors should have a luminance greater than ____ nit (50 foot-lamberts) | 170 nit |
| Secondary display monitors should have a luminance greater than ____ nit (30 foot-lamberts) | 100 nit |
| light-emitting, curved face, scanned electron beam, veilling glare, spot pixels(phosphors) | CRT |
| light-modulating, flat face, active matrix address (TFT), pixel cross talk distortion, square pixel | LCD |
| refers to images displayed on computer monitor | soft copy |
| ration of width of display to the height of the display | aspect ratio |
| how many times each second the monitor rewrites the image on display | refresh rate |
| is an electronic vacuum tube used for displaying electrical data in the form of images or videos on the screen. it is used in electronic devices such as tvs, computer monitors, radar, and oscilloscope tubes. | Cathode ray tube (CRT) |
| a component of CRT, is used for generating, controlling and focusing the beam of electrons enclosed in a vacuum tube. internally consists of five components, heater, cathode, control grid, accelerating anode, and focusng anode | electron gun |
| a component of CRT, the horizontal deflection plates deflects the electrons horizontally | horizontal deflection plates |
| a component of CRT, deflects electrons vertically | vertical deflection plates |
| T/F both the horizontal and vertical deflection plates control the path of electron beam so that it can be directed towards a specified position on the phosphor coated screen | TRue |
| a component of CRT, is a transparent screen coated on one side with a phosphor that grows brightly when exposed to cathode rays | fluorescent screen |
| T/F to offset high noise levels, the CRT monitor must have a low SNR | False must have a high SNR |
| type of glare that occurs when ambient or room lighting reflects off of the surface of the monitor or display screen | reflective glare |
| CRT monitor screen have an internal glare called _____. electron backscatter, lateral leakage of light from the phosphor crystals within the phosphor layer. | veiling glare |
| T/F a disadvantage of LCD is that it becomes defocused over time bc electron beam is used to create the image | False, an advantage of LCD is that it does not defocus over time bc no electron beam is used to create the image. |
| T/F LCD has better grayscale definition than CRT | True |
| T/F LCD increases the effect of ambient light on image contrast (less contrast resolution) | False, LCD better reduce the effect of ambient light on image contrast (greater contrast resolution) |
| T/F LCD produces a higher lvl of luminance than CRT's (up to 700 nit) and less noise | TRue |
| T/F Disadvantages of LCD include greater viewing angle | False, usually 40 degrees either side of a line that is perpendicular to the center of the faceplate. |
| T/F an advantage of LCD is that it is not subjected to dead pixels | False, it is subjected to dead pixels. |
| a viewing condition, primary workstations are used for official interpretation of medical images and must follow established guidelines to include maximum lum lvls of at least ____ candelas per meter squared. | 171 candelas per meter squared |
| _____ workstations are used by technologist to view a digital image. workstation is often in a brightly lit work area while the radiologist high res monitors are in a dimly lit reading room. | secondary workstations |
| universal standard for exchaning medical imgs among modality, workstations and archives. contains pt name, iden info, date of procedure, ordering MD and location | digital imaging and communications in medicine DICOM |
| RIS is under | Epic |
| data base that handles the workflow of the system by moving images to storage for viewing at workstation then back to the archive | PACS image manager |
| T/F PACS image manager populates information to the electronic medical record (EMR) | TRue |
| Government standard where it uses 7 layers of encryption | Health Level 7 (HL7) |
| in a clinical setting EMR is | Epic |
| The displayed value on the processed digital image that indicates the level of exposure received on the IR. | exposure indicator value |
| The evidence of motion on a radiographic image is seen as: | Image blur |
| Increase grid ratio, AOFC, has what effect on the img? a. increase RE and increase img contrast b. increase RE and decrease img contrast c. decrease RE and increase img contrast d. decrease RE and decrease img contrast | C. decrease Receptor exposure and increase image contrast |
| Foreshortening occurs when | The part is angled in relationship to the IR |
| Elongation occurs when: a. The part is angled in relationship with the IR b. Tube is off-centered or angled c. IR is angled and not parallel with part d. Both b and c e. All of the above | D. both b and c |
| Defines differences in pixel brightness values between various areas of the image: | image contrast |
| Increasing tube filtration results in an x-ray beam with ____________ quantity and ______________ energy. | Less; higher |
| The anode heel effect: | due to x-ray absorption at the surface of the anode |
| All other factors remain constant, an increase in exposure time has what effect on receptor exposure? | increase receptor exposure |
| An advantage of PACS is that it allows images to be: | sent to several workstations and monitors simultaneously |
| Increasing the atomic number of tissue (Z#) has what effect on x-ray photon transmission? | decrease |
| on the flash light looking diagram, it points to the the end of the flighlight where light comes out. | Fluorescent screen |
| The set of computer standards used to permit a wide range of digital imaging systems to ensure that images taken at one facility are able to be viewed correctly at another facility is termed: | DICOM |
| Increasing the size of the pixel has what effect on spatial resolution? | decrease |
| This post processing feature allows the technologist to adjust the radiographic image brightness on the processed images. | window level |
| If the distance from the source is decreased by a factor of 2 (one half), the mAs must be ______to maintain the same receptor exposure. | decreased by a factor of 4 |
| When comparing viewing monitors, increased signal-to-noise ratios results in: | sharper images |
| The configuration formed by a scanning electron gun in a CRT is termed a/n: | raster pattern |
| In order to eliminate reflective glare when using an image viewing device, the technologist or radiologist should: | view the image at 90 degrees, rather than from an angle |
| T/F The technologist should manually adjust all radiographic images (window level/window center) at the QC station prior to sending to the radiologist for viewing. | False |
| The exposure rate of the x-ray beam is BEST controlled by: | milliamperage |
| The four steps of creating an image with computed radiography are: | exposure, stimulate, read, and erase |
| This grid error results when the central ray is not aligned from side to side with the center of the focused grid. | Off-center |
| The type of display monitor that contains an electron gun and accelerating grids: | cathode ray tube |
| Primary display monitors should have a luminance greater than: | 170 nit |
Created by:
Btran573