ann review Flashcards
what measures tube current?
mA meter
what is surrounded by the negatively charged focusing cup?
filament
Which device reduces voltage and provides current to produce an electron cloud or space charge at the filament?
step down transformer
What type of x-ray machine uses a continually decreasing mA for the shortest times possible?
falling load generator
The speed of x-rays is based on:
The fact that they are a form of electromagnetic radiation
The test that measures the accuracy of adjacent mA stations is:
it must be accurate to within:
exposure linearity
10%
The test that measures the accuracy of successive exposures is:
it must be accurate to within:
Exposure reproducibility
5%
What device always delivers the shortest exposure time possible?
Falling load generator
What is the most commonly used AEC?
ionization chamber
The primary type of grid used in diagnostic imaging is:
focused
The primary purpose of filtration is:
RADIATION PROTECTION MOTHER F-ER!!!
The electricity provided to the radiology department operates at:
120 pulses per second
Resolution of the television system may be measured using the following tool(s):
Resolution test pattern
Fluoroscopy exposure rate may not exceed:
100 mGya per minute
what is electrostatics?
Electrostatics is the study of electric charges at rest
Electrostatic charges concentrate on a conductor in the ares of greatest curvature
____________________ is done during preprocessing to correct for an irregular pattern over the image.
flat fielding
__________________ is corrected by the application of an offset voltage.
image lag
The two principal characteristics of a medical image are __________.
spatial resolution and contrast resolution
The portion of useful image-forming x-rays is referred to as the ____________>
signal
The number of gray shades that an imaging system can reproduce is called its ______________.
dynamic range
The laser is one of the features of the computed radiography reader.
optical
The human visual system can distinguish _______ shades of gray.
30
The four steps of creating an image with computed radiography are .
metastable state, stimulate, read, and erase
The following computer component temporarily stores data for processing.
hard disk drive
he dynamic range determines the degree of in the image.
contrast resolution
The computed radiography image has:
narrow exposure latitude
improved contrast resolution
The ______________ digital imaging system uses the highest dynamic range.
mammography
patial frequency is used to describe the quality of spatial resolution in terms of _____________.
line pairs
Spatial resolutuion is determined by the ratio of ____ to ____
FOV
matrix size
In digital imaging, spatial resolution is ultimately limited by ______________.
pixel size
If there were such thing as a perfect imaging system, the MTF would be equal to __________.
1
If digital radiography imaging system has a spatial resolution of 10 lp/mm, what is the pixel size of that system?
.05mm
Europium is the of the photostimulable phosphor.
activator
Histogram selection is done __________________.
by the radiographer before each exam
If an image receptor has a high probability if interacting with the x-ray beam, then it has a high __________.
DQE
How can the radiographer tell if the automatic exposure control (AEC) is calibrated properly when using CR imaging plates?
The exposure indicator number is in the optimal range
Edge enhancement can be applied to a digital image to improve which of the following?
The contrast along the edges of a structure
extreme overexposure (at least 4X) will create “black holes” in the low density, tissue areas of a digital image. The proper term for this effect is:
saturation
What determines high contrast resolution in a digital image?
High exposure and low noise
If you are going to put more than one image on a CR cassette, which of the following it true?
- The unexposed areas must be covered with lead
2. Four collimated borders must be around each image
In digital radiography, Nyquist is referring to which of the following?
The sampling frequency of the digital data
Random background interference that is often referred to as “snow” on a television is called what?
noise
Smoothing can be applied to a digital image to mask which of the following?
noise
The photostimulable phosphor that is used in a CR’s imaging plate is a barium fluoride compound that is doped with:
europium
The quality of a digital image depends on which of the following?
- Spatial resolution
- Brightness
- Contrast
The size of the pixel produced when a CR imaging plate is read depends on which of the following?
- The speed of the imaging plate as it passes through the reader
- The frequency with which the data is sampled
- The dimensions of the laser beam
To prevent a moire pattern in your computed radiography (CR) digital image, it is best to have the grid lines running to the direction of the laser beam.
perpendicular
What is the technical name for a computed radiography imaging plate?
Photostimulable phosphor plate
Which of the following could cause a histogram analysis error?
- Improper collimation
- Off-focus/scatter radiation
- Grid cut-off
what is the distance measured from the center of a pixel to an adjacent pixel called?
pixel pitch
what is the measure of spatial resolution called?
spatial frequency.
line pairs per mm
what is the formula to determine pixel size?
fov / matrix size
the TFT array is divided into ______ which obtains electrical charges that are sent to the ADC for digitization
detector elements DEL
what is the percentage of X-ray capture called?
fill factor
what is an image displayed as rows and columns called?
matrix
what determines how often the analog signal is reproduced in its discrete digitized form?
sampling frequency
what is the ability to distinguish between small objects having similar subject contrast and number of shades of gray called?
contrast resolution
what determines the number of shades of gray that can be displayed?
bit depth
what is the mathematical procedure for measuring resolution?
modulation transfer function
high MTF=improved visibility
1 = maximum difference in brightness level
0= no difference in brightness level
what is the measurement of efficiency of an IR in converting X-ray exposure it receives to a quality image?
detective quantum efficiency DQE
what is the post processing function that compensates underexposed areas by making them darker and overexposed ?
equilization
following histogram analysis, _______ provides a method of altering image to change display of the digital image
look up table
_________ is required to reduce data file size and increase transmission time
image compression
what can lead to an exposure field recognition error?
when the X-ray field is not properly collimated, sized or positioned
this type of grid cut off causes significant underexposure to the lateral edges of the image:
upside down focused
this type of grid cut off from either the tube or IR being angled, and it causes a decrease in radiation exposure to the IR and is the most common type:
Off level
this type of grid cut off occurs when CR is not aligned from side to side w/ center of a focused grid and appears as an overall loss of exposure:
off center
this type of grid cut off occurs when using SID outside of recommended focal range and appears as a loss of exposure at the periphery of the image:
off focus
_______ is a program in radiology that addresses customer service, image interpretation, accuracy of diagnosis, and distribution of radiologists reports:
quality assurance
__________ is a program that specifically addresses safe and reliable operation of equipment:
quality control
CR perpendicularity cannot be misaligned by more than ______
1 degree
what is the TG18-QC test pattern used for?
tests display monitor
________ is the measurement of light intensity emitting from the surface of the monitor, expressed in units of candela per square meter.
luminance
the addition of a grid will ______receptor exposure, _______ density and _________ contrast.
decrease
decrease
increase
the _____ focal spot is where the electrons in the tube bombard the target and the ______ focal spot is the area that is viewed and measured directly below the target
actual
effective
an increase in angle of the tube will ______ receptor exposure, ______ spatial resolution and ______ distortion.
decrease
decrease
increase
this detector is made up of cesium iodide amorphous silicon:
indirect capture
this detector is made up of amorphous selenium:
direct capture
____ monitor includes an electron gun receiving the video signal that scans the phosphor layer inside the glass front
CRT
________ monitor contain several layers including liquid crystal layer sandwiched between polarizing layers
LCD
________ monitors consist of a thin layer of pixels that contain three neon and xenon gas filled cells
plasma
what are the 4 layers of the PSP CR imaging plate?
- support layer/base
- reflective layer
- phosphor layer
- protective layer
________ is a photosensitive receptor and electronics embedded into substrate material in a silicon chip, coupling devices that act as a camera
CCD charged coupled device
_________ is a special type of memory chip that uses a small rechargeable or lithium battery to retain info about a personal computers hardware while the computer is turned out
CMOS complementary metal oxide semiconductor
_________ maintains consistent image brightness despite over/underexposure
rescaling
________ is the process of assigning a value to a dead pixel based on recorded value of adjacent pixels
dead pixel correction
