UNIT 3 REVIEW ASSIGNMENT AND EXAM Flashcards
A QC test performed by Radiographers in order to assess for detector malfunctions and flaws in the acquisition process
A. Flat Field Uniformity tests
B. Exposure field recognition
C. Partitioned pattern separation
D. Windowing
A. Flat Field Uniformity tests
Flat field uniformity , gain or off set gain corrections attempt to even out the signal across the area of the image field. The variance of the signal can be caused by dead or malfunctioning pixels, rows or columns; image lag , anode heel effect or calibration errors.
Exposure field recognition separates areas of the image by scatter noise, raw exposure and midrange gray levels for histogram analysis.
Partitioned Pattern Separation or segmentation is used in CR to separate multiple exposures taken on a single IP.
Irrelevant contrast that exists in an image is termed _________ and is measured by _____________
A. Contrast noise; CNR
B. Signal noise; SNR
C. Region of interest; area in mm
D. Standard deviation; mean
A. Contrast noise; CNR
Irrelevant contrast that exists in an image is contrast noise; measured by the contrast to noise ratio (CNR). SNR is the measure of the ratio of noise to the signal in a system. The mean is the average of the pixel values in a region of interest measurement (ROI). ROI’s are used by radiologists to help identify the size and consistency of tissue within a specified region. The CNR can be calculated by region of interest measurements (ROI) usually by the medical physicist.
Which type of detail processing is better suited to remove random noise such as quantum mottle?
A. High-pass filters
B. Intensity processing
C. Frequency processing
D. Kernels
D. Kernels
Kernels in the spatial domain are better suited to reduce random noise such as quantum mottle. Low-pass filters in the frequency domain are better suited for removing periodic noise, such as electronic noise or aliasing.
The type of algorithms used to take input digital data and produce output analog data in the form of an image are known as:
A. Image to information transformations
B. Image to image transformations
C. Information to image transformations
C. Information to image transformations
Identify the labeled areas of the histogram in the image below:
Smin
Smax
Tail
Threshold
Value of interest
A. Threshold
B. Smin
C. Value of interest
D. Smax
E. Tail
Which of the following is/are test pattern(s) that could be used to assess the characteristics of a medical image viewing monitor?
SMPTE
ADC
DICOM
TG-18
SMPTE
TG-18
In digital imaging, image contrast is primarily controlled by
A. LUT
B. TFT
C. kVp
D. DAC
A. LUT
Which of the following are considered operator adjustments that can be made to a processed image? (select all that apply)
Flat fielding or gain corrections
Histogram analysis
Partition pattern separation (segmenting)
Image zoom
Image invert
Image flip or rotate
Annotation
Image zoom
Image invert
Image flip or rotate
Annotation
A function that estimates an unknown value from two or more known values by taking an average of the values surrounding it is called
A. Fourier Transform
B. Histogram
C. Interpolation
D. Convolution
C. Interpolation
A term used to describe the application of the LUT is
A. Post-processing
B. Gradient processing
C. Brightness processing
D. Frequency processing
B. Gradient processing
Gradient processing can be applied on two occasions: first, during default preprocessing when the anatomic LUTs are applied; then again anytime the displayed image is windowed by the operator
The function of the TFT panel in the LCD monitor is to:
A. Turn the backlight on and off
B. Improve spatial resolution
C. Apply current to liquid crystal
D. Convert the light to electrons
C. Apply current to liquid crystal
Edge enhacements are made in the spatial domain using:
A. Flatfield Corrections
B. The LUT
C. The Fourier Transform
D. Kernels
D. Kernels
Which of the following are considered hard copies of images? (select all that apply)
Displayed on a monitor
Paper
Film
Paper
Film
A region of interest (ROI) is used in digital imaging to:
A. Provide appropriate contrast to the image
B. Rescale the histogram
C. Measure the Contrast to Noise Ratio (CNR)
D. Determine the total SNR
C. Measure the Contrast to Noise Ratio (CNR)
Match the following histogram analyses with their definitions.
Type 1 Histogram
Type 2 Histogram
Type 3 Histogram
-Histogram has a spike in the white side and sometimes a tail. Used for contrast studies such as SBS and BE.
-Histogram has a tail. Used for images with large areas of direct exposure.
-Histogram has no spike in the white or the black region. Used for images in which anatomy fills the entire field.
-Type 1: Histogram has a tail. Used for images with large areas of direct exposure.
-Type 2: Histogram has no spike in the white or the black region. Used for images in which anatomy fills the entire field.
-Type 3: Histogram has a spike in the white side and sometimes a tail. Used for contrast studies such as SBS and BE.
A method for scoliosis imaging that involves three images that are taken and patched together is referred to as:
A. Dual energy subtraction
B. Unsharp masking
C. Digital Subtraction Angiography
D. Image stitching
D. Image stitching
In CR three IPs are aligned with a special mesh grid to ensure registration between images. These are usually taken with one exposure. This is a disadvantage with the central ray not centered over the extreme ends of the body part. In DR the same detector is used, moved from one location to the next, requiring only two exposures. See the posted manufactures brochures on Image Stitching for more information on how the major manufactures achieve this
What is the difference between masking or cropping and exposure field recognition (EDR/EFR)?
A. EDR /EFR is a preprocessing function that separates exposure areas assisting with accurate histogram analysis, while masking is a post processing function that does not improve histogram analysis.
B. Masking is a post processing function that is used to take the place of collimation and improves patient dose, while EDR/EFR does not improve patient dose.
C. There is no difference. They are the same thing.
D. EDR/EFR and masking are both preprocessing operations that improve the contrast in the image, but masking does it better
A. EDR /EFR is a preprocessing function that separates exposure areas assisting with accurate histogram analysis, while masking is a post processing function that does not improve histogram analysis.
EDR /EFR is a preprocessing function that separates exposure areas assisting with accurate histogram analysis, while masking is a post processing function that does not improve histogram analysis.
Masking does not take the place of proper collimation and should only be done to reduce the effects of veil glare on the image.
In digital radiography, the latent image is acquired in _____________ form on the _______________
A. digital; monitor
B. digital; image receptor
C. analog; image receptor
D. analog; monitor
C. analog; image receptor
If a radiographer applied the ankle LUT to a chest radiograph, the image would likely demonstrate:
A. Extremely low resolution
B. Low contrast
C. High contrast
D. A loss of contrast
C. High contrast
A chest image processed with an ankle LUT would demonstrate high contrast. This is because the reference ankle LUT, associated with the procedure algorithm for an ankle, is designed to display appropriate high contrast for an extremity image. The computer software will rescale or modify the brightness and contrast to match the selected procedure algorithm regardless of the actual input. However, the radiographer can correct for improper histogram selection prior to sending the image to PACS.
A histogram is:
A. A post processing technique
B. A table of numbers that represents a “normal” image for the selected procedure
C. A graph that plots the number of pixels assigned to each code value in the digital image
D. Created using a frequency processing technique
C. A graph that plots the number of pixels assigned to each code value in the digital image
Smoothing filters remove: (select all that apply)
Details
Fine edges
Noise
Large structures
Details
Fine edges
Noise
Smoothing filters remove the fine edges of structures, removes noise and removes details. This are typically referred to as low pass filters because, small objects with high frequency are filtered out and large low frequency objects are allow to pass. Smoothing filters are used to remove noise in an image.
High pass filters do the opposite, they filter low frequency objects such as low contrast objects and leave high frequency objects or fine details. These algorithms are used to sharped fine structural lines, but introduce more noise in in the image
A special type of imaging that produces soft tissue only and bone only images simultaneously:
A. Digital tomography
B. Digital Subtraction Angiography
C. Dual Energy Subtraction
D. Double Exposure Radiography
C. Dual Energy Subtraction
Dual energy subtraction uses a high energy and a low energy images to produce separate image of bones and soft tissues. There are two methods: In the first method, two separate images are produced at different kVp levels and the tissues of interest are subtracted out. The advantage of this method is that the tissue selected images have better signal. The disadvantages are that the patient dose is higher and there may be mis-registration b/t images due to patient motion. 2. In the second method, one image is produced with a special filtered cassette for high and low energies and the tissues of interest are subtracted. The disadvantage of this method is the the tissue selected images have more noise which may lead to obscuring of detail.
Sources of noise in an imaging system include: (select all that apply)
Dark current
High SNR
Dark noise
Appropriate shielding
Low signal
Light scatter in indirect capture DR systems
Dark current
Dark noise
Low signal
Light scatter in indirect capture DR systems
The bit capacity of the quantizer in the ADC represents the:
A. The pixel bit depth of the system
B. The dynamic range of the system
C. Number of gray levels the system can render
D. All of these
D. All of these