Imaging Final 3
If the field of view is 500 mm and the matrix is 1024, what are the pixel dimensions?
0.49mm x 0.49mm
A method of describing the strength of the radiation exposure compared with the amount of noise apparent in the digital image is the:
signal-to-noise ratio
A 10-bit depth can display how many shades of gray?
1024
Which of the following is the sequence of events, from beginning to end, of what happens in the CR reader unit: 1) Analog electrical signal is sampled and digitized 2) Stored energy is released as visible light 3) PMT converts light energy to electrical signal
2,3,1
Which of the following is the sequence of events, from beginning to end, for production of a DR imaging using direct conversion detectors? 1) Image matrix is formed in computer 2) Charge is briefly stored in TFT array 3) Exit radiation is converted to electrical charge 4) Electronic signal goes to ADC
3,2,4,1
Diagnostic interpretation should be done at a high-resolution ___ display monitor.
5 megapixel
Digital imaging processing refers to:
A computer manipulations applied to digital images
Pixel bit depth is determined by the:
ADC
Soft copy viewing means that the image is being viewed:
At a computer
The monitor matrix size should be ___ the image matrix size.
At least as large as
Based on the histogram analysis, consistent image brightness is accomplished through:
Automatic rescaling
The communication standard for information sharing between PACS and imaging modalities is the:
DICOM
Increasing the number of line pairs per millimeter resolved in the imaging system results in:
Higher spatial frequency and increased spatial resolution
The number of bits that determines the amount of precision in digitizing the analog signal and the number of gray shades that can be displayed in the image is the:
Bit depth
The ___ provides a method of altering the image to change the display of the digital image.
Lookup table
An example of a scintillator used in an indirect conversion detector is:
Cesium iodide and gadolinium oxysulfide
A method of describing the contrast resolution compared with the amount of noise apparent in a digital image is the:
Contrast-to-noise ratio
The higher the DQE of a system, the radiation exposure required to produce a quality image is:
Decreased
Decreasing the window level will result in an image with:
Decreased brightness
With CR, a higher sampling frequency results in ____ pixel size and _____ spatial resolution.
Decreased; increased
The measurement of the efficiency of an image receptor in converting the x-ray exposure it receives to a quality radiographic image is the:
Detective quantum efficiency
Which of the following is not part of a CR reader unit? A) Optical system B) ADC C) Photodetector D) Developer tank
Developer tank
A value that reflects the difference between the desired or target exposure to the IR and the actual exposure to the IR is the:
Deviation index (DI)
The DICOM GSDF is used to evaluate the:
Display monitor
The ability of the detector to accurately capture the variety of photon intensities in the remnant radiation is:
Dynamic range
The post processing technique improve the visibility of small, high contrast structures.
Edge enhancement
Which of the following is not a component of the CR IP? A) emulsion layer B) support layer C) phosphor layer D) protective layer
Emulsion layer
In CR imaging, the ___ of the imaging plate is scanned.
Entire area
With CR, when the x-ray photons are absorbed by the phosphor, the ___ atoms become ionized.
Europium
The numerical value indicating the level of radiation exposure to the digital IR is the:
Exposure indicator
An image with high SNR will have decreased detail visibility: T/F
False
Because digital imaging has a large dynamic range, significantly lower than necessary x-ray exposure will still result in a quality image. T/F
False
Bit depth is determined by the matrix size. T/F
False
Both CR and DR are electronic detectors that combine image capture and image readout: T/F
False
Exit radiation is converted to visible light with the direct conversion detector. T/F
False
There is no light produced with CR when radiation interacts with the IP. T/F
False
The percentage of x-rays that have reached the detector and have been captured is the:
Fill factor
___ can be removed from the Bucky and is used on the tabletop or stretcher.
Flat-panel detector
The communications standard for medical information is:
HL7
A CRT type monitor:
Has a fluorescent screen, uses an electron gun, and scans in lines
The size of a pixel is measured in:
Inches
The histogram analysis represents the ___ for different exposure controls.
Incidence of pixels
A system that can digitize and display a greater number of shades of gray will have ___ contrast resolution.
Increased
Which of the following results in improved spatial resolution?
Increased pixel density and decreased pixel pitch
With CR, a higher sampling pitch results in _____ pixel size and _____ spatial resolution.
Increased; decreased
With CR, a higher sampling frequency results in ____ pixel density and _____ spatial resolution.
Increased; increased
A large bit depth:
Increases contrast resolution
A large bit depth:
Increases the number of shades of gray
___ the CNR increases the visibility of anatomic details.
Increasing
___ the SNR increases the visibility of anatomic details.
Increasing
Immediately before leaving the CR reader unit, the IP is exposed to:
Intense white light
With a fixed matrix CR reader system, changing to a larger IP, for the same FOV, will result in:
Larger pixels
LCD stands for:
Liquid Crystal Display
Which of the following passes light through liquid crystals to display the image on the glass faceplate?
Liquid crystal display monito
Increasing the window width will result in an image with:
Lower contrast
What is the term generally used to describe the emission of light from a substance as the result of stimulation by radiation?
Luminescence
Which of the following is not accomplished through the histogram analysis?
Manipulation of image contrast
The distracting area of increased brightness surrounding a collimated image can be removed from the displayed digital image by:
Masking, shuttering, electronic collimation
A combination of rows and columns (array) of pixels is called a:
Matrix
The greater the pixel bit depth, the ___ the digitization of the analog signal, and the ___ the number of shades of gray available for image display.
More precise; greater
All of the data from the entire IP (including scatter outside the exposed field) may be included in the histogram analysis if:
Only one edge of the collimated field is identified
The computer system designed to distribute, store, and display digital images is:
PACS
The ___ collects, amplifies, and converts visible light to an electronic signal.
PMT
Which of the following is not a component of a flat-panel detector?
Phosphor layer
The emission of light when stimulated by a high-intensity laser beam is:
Photostimulable luminescence
This material is composed of barium fluorohalide and makes up the primary component of the CR IP.
Photostimulable phosphor
The pixel spacing or distance measured from the center of a pixel to an adjacent pixel is called the:
Pixel pitch
With CR, trapped electrons are:
Proportional in number to the tissue's x-ray absorption and released during the readout stage
A high SNR means that the:
signal strength is high
Which of the following exposure indicators has an inverse relationship with exposure to the IP? A) EI (Carestream) B) IgM (Agfa) C) S number (Fuji) D) All have an inverse relationship
S number (Fuji)
Which of the following changes in the exposure indicator values does not represent a doubling of radiation exposure to the IR? A) S number (Fuji) changing from 200 to 400 B) S number (Fuji) changing from 400 to 200 C) EI (Carestream) changing from 1200 to 1500 D) EI (Carestream) changing from 1500 to 1800
S number (Fuji) changing from 200 to 400
The distance between the analog points being sampled is the:
Sampling pitch
The indirect conversion detector uses:
Scintillator and photodetector
This post processing technique reduces the visibility of image noise
Smoothing
DR imaging systems briefly store the electrical charge in the:
TFT
The ___ array is divided into square detector elements (DEL).
TFT
Overexposing a digital image receptor may result in a quality image, but:
The ALARA principle has not been followed
Which of the following is true concerning computed radiography imaging plates? A) The CR cassette houses the imaging plate B) The radiation exiting the patient interacts with the imaging plate C) The photon intensities are absorbed by the phosphor D) All of the above
The CR cassette houses the imaging plate, the radiation exiting the patient interacts with the imaging plate, and the photon intensities are absorbed by the phosphor
If the field of view is increased for a fixed matrix:
The pixel size is increased
Once the data is in digital format, there is not difference between image processing and display between CR and DR: T/F
True
The DQE is higher for DR when compared to CR. T/F
True
The DR system does not require a separate reader unit. T/F
True
The dynamic range of a digital imaging system is significantly larger than a film-screen system. T/F
True
The spatial resolution of flat-panel receptors is generally superior to that of CR. T/F
True
With an FPD, electrical charges from each DEL are read out separately: T/F
True
The range of the histogram data set that should be included in the displayed image is determined by the:
VOIs
The DR detector array is typically located:
Where you would normally find the Bucky tray
Because digital IRs have a linear exposure response and wide dynamic range, raw data images appear:
With low contrast
Which of the following is true about the indirect conversion DR systems?
X-rays are converted to light then converted to electrical charges
If the matrix is increased for a given FOV:
a. spatial resolution is increased
The CR phosphor layer is composed of:
barium fluorohalide with europium
The pixel bit depth determines the image's:
contrast resolution
Compared with film-screen detectors:
digital IRs have a much wider dynamic range.
The CR latent image consists of:
electrons trapped in the phosphor layer
In the CR reader unit, the IP is scanned with a(n):
helium-neon laser beam
Digital image quality is improved with:
larger size matrix and smaller size pixels
An MTF of 1.0 means:
maximum difference in brightness levels
The measure of the imaging system's ability to display the contrast of anatomic objects varying in size is the:
modulation transfer function
The number of pixels per unit area is called the:
pixel density
How often the analog signal is digitized is the:
sampling frequency