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RAD Final Exam

Terms in this set (100)

What interfaces with the RIS, HIS, and PACS?
Health Level 7
What is the best viewing conditions for a primary workstation?
Minimal levels of room light
What reduces the size of the image file and affects image quality?
Compression ratio
What occurs when there is lack of signal strength on a TV monitor?
Snow
What is the term used to describe the steady increase of exposure to patients because of the increased latitude for overexposure errors in digital imaging?
Dose creep
What is a compression type that is used when images are to be sent outside of the network where the images were originally acquired?
Lossy compression
T/F
The display screen can affect the size distortion and magnification of an image.
True
What does PACS stand for?
Picture Archiving and Communication System
T/F
With digital imaging, mAs only must be increased to prevent repeating exposures because of quantum mottle.
False
What is the result if the anatomical region is not represented accurately?
Shape distortion
What system has the highest detective quantum efficiency (DQE)?
Direct radiography (DR) systems
What does the capacitor do in the thin-film transistor (TFT) of an LCD monitor?
Maintains the brightness and continuity of each pixel
T/F
The EI value is representative of the patient dose.
False
T/F
Reduction in patient dose has occurred with computerization of radiography.
True
What is the purpose of a grid in digital imaging?
To improve signal-to-noise ratio
What is the main reason for using high kVp and low mAs with digital imaging systems?
Decrease patient exposure
What is the primary factor influencing contrast using digital radiography systems?
Look-up table (LUT)
What is the primary cause of scatter radiation?
Patient size
What is the result if the detective quantum efficiency (DQE) is too high?
Mottled appearance
What is graphed on a histogram?
Number of pixels of an image at a given density
A wide window width:
Produces a lower-contrast image
What is the dose-area product a measurement of?
Patient dose of the volume of tissue irradiated
Why is it important to demonstrate four-sided collimation on direct capture digital radiography?
So data outside of the x-ray field can be disallowed in construction of the image histogram
What is accompanied with low signal-to-noise ratio?
High noise
What is the Nyquist frequency?
The sampling frequency that the imaging plate is scanned by the laser beam
What indicator for exposure dose cassetteless digital systems use?
Dose -area product
What monitor is necessary for viewing by radiologists for interpretation?
2 megapixel
What term is used to describe any unwanted information of the radiographic image?
Artifacts
Higher detective quantum efficiency (DQE) will result in what?
Higher image quality and lower patient dose
What is a frame grabber?
Digital acquisition that digitizes an analog signal received from the image receptors
How much of the image plate should be exposed to decrease the possibility of exposure indicator errors?
30%
What digital imaging scale uses a calibration factor?
Proportional scale
T/F
CR and DR have greater exposure latitude than film-screen imaging.
True
T/F
The EI values in all digital imaging systems are uniform.
False
What will result if insufficient mAs is used for a projection?
Quantum mottle
What does an exposure index (EI) indicate?
Amount of radiation reaching the detector
T/F
Using optimal kVp, the AEC will receive the exposure to the detectors and stop the exposure when the correct amount of exposure is read.
True
What are the two domains used for processing a digital image?
Spatial and frequency
What is not considered a fundamental component of a PACS?
Reading room
What does the computer use to produce an "ideal" image output?
Look-up tables
What does the spiked portion or "tail" of a histogram represent?
The area outside of the anatomy within the collimated field
What is seen if the sampling rate in line pairs per millimeter is the same as the line resolution of the imaging plate?
Moire artifact
T/F
Technique corrections and mottle prevention should only be made by changing mAs.
False
Underexposure will result in what error?
Quantum noise
What kVp setting is discouraged when imaging extremities with digital radiography?
Less than 60 kVp
How much overexposure is required before a digital system becomes overwhelmed with data and reaches saturation levels?
8 to 10 times
T/F
Centering the anatomy correctly in the image receptor can be ignored when using digital.
False
All manipulation of the digital image after initial corrections are made is known as:
Postprocessing
Using an inversely proportional scale, with 200 being the ideal exposure, an S number of 400 would indicate:
The exposure was half the amount of the ideal exposure
What is the primary workstation?
Where the official interpretation of the digital image takes place
What is the term used to describe the amount of time it takes to reconstruct the next frame in a liquid crystal diode (LCD) display monitor?
Refresh time
What is signal-to-noise ratio?
Method used to express noise in comparison to signal strength
When reversing the blacks and whites in the image, it is known as:
Image inversion
What occurs when the Nyquist frequency closely matches that of the grid frequency?
Moire or aliasing artifact
T/F
It is best to annotate the right or left side after exposure.
False
T/F
An under exposure will not cause visible mottle in the image.
False
T/F
If the image has the correct appearance on the display monitor, the EI does not need to be reviewed.
False
When a digital image is excessively overexposed, what is the result?
Saturation
What is the name for the graphic representation of optimal densities within a collimated field known as:
Histogram
What is the exposure latitude for digital imaging?
-50% to +400%
Image analysis of digital imaging process consists of all but what?
High-pass filtering
The liquid crystal material used in liquid crystal diode (LCD) displays are linearly shaped and are electronically charged making them:
Nematic
What does the computer use to improve the contrast in the digital image?
Dynamic range compression
T/F
AEC does not need to be used correctly with DR.
False
When raw digital image data are corrected in the computer, it is known as:
Preprocessing
What does a mottled appearance on a radiograph indicate?
Not enough x-ray photons reaching the imaging plate
What is an effective way to manage the size of image files for transmission and storage of digital imaging?
Compress the digital image data
What can result if multiple fields are done on one computed radiography (CR) plate without an area of "blank white" between the images?
Histogram error
Why are barium fluorobromide, cesium iodide, and amorphous selenium used in digital imaging detectors?
They have high atomic numbers
What is the compression ratio of lossless compression?
2:1 to 3:1
T/F
In CR imaging the Moire artifact is caused by the Nyquist frequency.
True
What is the purpose of Digital Imaging and Communications in Medicine (DICOM)?
Specifies standards for how imaging information objects are searched, stored, and retrieved
What is the universally accepted standard for exchanging medical images among the modality, workstations, and archive?
DICOM
DICOM standards are used to:
Ensure that various digital imaging systems are compatible with each other
T/F
Because CR systems recognize exposure to the IR, the technologist can use higher kVp and lower mAs to produce a diagnostic image.
True
What is the result of insufficient kVp?
Under penetration
What property do the liquid crystal compounds have that allows them to flow?
Viscosity
What error does digital imaging have most latitude for?
Overexposure
What is the term used to describe the amount of time the pixel takes to change its brightness?
Response time
T/F
RAID systems protect archives of medical images from accidental loss.
True
What is the result of underpenetration?
Inadequate information
How is dose-area product determined?
Multiplying the field size by the dose
In digital imaging, what is density referred to as?
Window level
T/F
When the computer reads the data from the IR or IP, it will compensate for any scatter by using processing algorithims.
True
What is the term used to describe image receptor and central ray alignment?
Detent
Which of the following is not considered part of a patient's demographics?
Patient occupation
What is NOT a component of image enhancement?
Normalization
Where is all relevant information attached in digital imaging?
To the digital image and stored into PACS
What is another term for magnification in radiographic imaging?
Size distortion
T/F
To avoid image mottle, expose all digital images without a grid.
False
Where the rows and columns of the conductors of an liquid crystal diode (LCD) display intersect make up a:
Pixel
T/F
Scatter radiation resulting from the x-ray beam will always result in a darker image on CR or DR systems.
False
What was developed so that medical imaging display monitors were brighter, sharper, and have high-speed response times?
Active matrix liquid crystal display (AMLCD)
What is the purpose of high-pass filtering?
To sharpen a blurred input image in the spatial domain
What interfaces with the RIS, HIS, and PACS?
Image manager
What is the term used for adding text to an image after processing?
Annotating
What is the minimum frame rate the human eye requires so there is no appearance of flicker?
20 frames per second
A PACS system is responsible for __________ digital images.
Transmitting and storing
T/F
With digital imaging, the field size must be large enough so that at least 30% of the image receptor is exposed.
True
With digital imaging, the use of high kVp must be avoided because there will be a longer gray scale.
False
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