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Mod 1,2 4,6,9 videos
Imaging 2. Videos for midterm
Question | Answer |
---|---|
______ of a DR image is equal to the term "density" used to describe appearance of analog images. | brightness |
______ is a phosphor used for intensifying screens | calcium tungstate |
_______ measures amount of exposure needed to achieve a specific density | relative speed |
Decrease exposure level needed to achieve optical density reflects a/an ______ in receptor speed | increase |
Direct exposure film has a _____ silver content than film used with intensifying screens | higher |
Term to describe speed of a digital imaging system | speed class |
Accurately create output signal that matches the input is called | DQE |
Portion of TFT that collects individual electrons? | TFT |
Matrix is composed of _____ | dels |
# of electrons deposited in the DEL corresponds to the amount of .....? | radiation that strikes each area |
Gas filled CT detectors have a _____ acceptance angle than scintillator based detectors. | smaller |
Receptor with _____ DQE can produce optimal images with less radiation exposure | highest |
Increased absorption efficiency has what effect on the DQE of a receptor? | increases the DQE of the receptor |
Spatial resolution can be measured with _____/mm or ____/mm | cycles/mm or lp/mm |
Increasing sampling frequency means what | more samples are taken per given unit of measurement |
Greater the sampling frequency, the ____ info is extracted from the IR | more |
Dynamic range is the IR's ability.... | to respond to exposure |
Range of exposures that will produce an optimal image is termed | exposure latitude |
Area of geometric blur surrounding the edges of an object is | penumbra |
_____ phosphor gives off light photons that strike the photocathode, causing electrons to be _____. These electrons strike the ____ pohophor, causing _____ to be emitted. | input, released. Output, light photons emitted. |
Why do LCD monitors excel over cathode ray tube displays? | They consume less energy and have better spatial resolution |
Workstation LCD display have a much _____ luminance than traditional viewbow illuminators. | lower |
Contrast capability of a monitor controls the ability of users to see ____ and ____ in a display image | lines and fine structures |
Modality worklist should include what 3 things? | modality, exam, pt location |
Adding black borders to display is called | shuttering |
pixel value manipulation to change the visual appearance is called | edge enhancement |
___ is a conventional measurement unit for dose equivalent when measuring radiation | REM |
_______ attach to the collimator and cast a shadow on the patient over the area where no radiation will be directed. They dont need touch the patient | shadow shields |
PBL is what | positive beam limitation. auto collimation |
Adjusting the image data to match the acceptable display data for a particular anatomical structure is known as | automatic rescaling |
Using ____ to adjust for grid ratio increase in DR is a viable way to adjust technique without affecting image quality | kVp |
Image noise limits the ______ of operation | speed class |
speed class of operation for analog IR is ___. | fixed |
Increasing kVp has what effect on the number of x-rays that the tube emits? | increases the #. |
Primary reason for filtration? | decreasing patient dose |
doubling distance reduces exposure by how much? | 1/4 |
Why does beam loose intensity traveling to IR? | divergence (NOT attenuation!) |
Using tighter collimation will reduce "undercutting"? T or F | true |
Grids reduce the amount of scattered radiation produced. T or F? | False. They reduce the amount of scattered radiation reaching the IR, not the PRODUCTION of scatter |
Grids main purpose is | improve contrast |
Grids transmit 90% of primary beam. T or F? | False. 60% |
Gridlines are less of a problem in DR than in anolog. T or F | false |
Grid cut off _______ the amount of radiation reaching the IR. | decreases |
Moire pattern occurs more often when using ____ dimension grids than when using ____. | short, long |
____ side of tube is the more intense side. | cathode |
Compton scatter interactions take place between x-ray and _____ shell e-. | outer shell e- |