EXAM #6 Tutor Questions Flashcards
• Overall resolution for imaging is measured as physicists as
MTF
• If in the remnant beam signal, what can reduce subject contrast and gray scale
Scatter
• How do you measure spatial frequencies
LP/mm
• Mathematically, the ratio of an images recorded contrast to the real subject contrast defines what
o MTF, closest to one as possible
• Which of the following is NOT a variable affecting sub contrast in remnant beam
o Focal spot
• For the computer to process an image, analog to digital is composed by a device called
o Analog to digital converter
• In general, digital imaging terms, brightness is what?
o Window level
• 1000x1000 matrix? How many pixels?
o 1mil pixels
• Compared to Work station, display stations can typically have
o Less resolution
• The selection of a narrow window width
o Increase contrast
• Dead pixels in the image is caused by failure of dead DELS
o Interpolation
• Flat field uniform corrections because of all the following except for what?
o Data clipping
• List of pixel values that make up a histogram, it’s called a permanent what?
o LUT
• A sub matrix that is passed over the original, executing a mathematical function is called what?
o Kernel
• Pattern recognition software is used for what?
o Segmentation
• Normalization is best described as the computer attempt to
o Make digital image look like a film image prior to any post processing
• Which of the following can a comp processing not do?
o Cannot change the pixel count
• Histogram correction errors are
o Not necessarily related to the radiographic technique used
• Histogram analysis failure is less common with DR, than CR, because DR algos include what
o Only the exposed DELS
• Histogram is the result when a digital image is sorted by
o Values contained by pixel
• Low freqs represent what?
o Large objects
• If you have dual energy subtraction, you either have variable filters or variable kVp
o High and low energy images (1 for bone and 1 for soft tissue)
• For all digital image systems, a restriction for lower limit for exposure
o Mottle
• Just as in conventional radiography, the what must have a high SNR
o Remnant beam
• In CR, substantial fog densities between 2 projections on the same plate can cause what
o Segmentation failure
• In any CR system, underexposure causes visible what?
o Mottle
• In the digital age, the main role of radiographic technique is what?
o Ensure proper SNR
• Which of the following is digital processing least capable of correction
o Pre-fogging on the CR plate
• Digital imaging system cannot compensate what
o Too low kVp
• Misunderstandings about radiographic technique, combined with broad exposure latitude in digital imaging systems
o Dose creep
• On a DR system. The field size for each image is what
o Adjusted by radiographer
• The weakest link in a radiographic imaging system chain
o Image display system
• How do you distinguish adjacent details from each other
o Visibility AND geometric
• What is not a form of image noise
o Signal
• What size is the smallest object that can be resolved by 2.5LP/mm
o Object
• As line pairs of a resolution template become smaller and closer together the overlapping of their penumbra causes loss of
o Contrast
• When the pixels of a digital imaging systems are small than the object in the focal spot, what’s the limiting factor for spatial resolution
o Focal spot size
• Which is the following is not a variable affecting noise
o Exposure time
• For radiography the brightness of a certain pixel within the image matrix of a digital image is related to what
o Attenuation
• In general, digital imaging terms, the range of gray scale is what?
o Window width
• If you have a 12 bit, ADC each pixel will have what?
o 2^12
• The larger the number of pixels in a matrix, what?
o Resolution
• As a displayed FoV is increased in size, spatial resolution or sharpness does what?
o Decreases
• The increased contrast res of digital imaging systems, allows demonstration of tissues with inherent subject contrast as low as what?
o 1%
• Which of the following would result in a displayed image that would be brighter?
o Decreased window level
• The general term for brightness and contrast is what?
o Windowing
• The term pre-processing is for the computer algos which represent what?
o Correct for image flaws in image acquisition
• In the active matrix array of a DR receptor plate, variations in alignment for multiple electronic amps and differences in resistance for varying lengths of wires coming from the hundreds of DELS
o Gain offsets
• Which of the following flaws are unique by CR but not DR
o Light guide variations
• Background exposure to a CR cassette and small amount of electronic current flowing through a DR system when no exposure is being taken
o Dark noise
• In a digital histogram graph, the vertical height along the plotted curve is against the y-axis, what?
o Number of pixels per value
• Which of the following systems req the greatest amount of preprocessing?
o DR
• On an image histogram, an unusual spike to left is what?
o Metallic objects
• In an algo designed to accentuate soft tissue densities will locate the VOI on a histogram
o Father to the right
• Comp distinguishes anatomy of interest from background from what
o Auto field recognition
• Segmentation failure is what?
o Partition pattern recognition
• For a large abdomen which completely covers the image plate, the histogram will appear how?
o No spikes
• Exposure field recog is normally done as what
o Histogram analysis
• The steeper the S-curve, the what?
o Higher image contrast
• The bins of data from the acquired image to be used for rescaling
o S-values
• Because the range of the Q scale, is outside the range of the discernment of the human eye this allows for what of the image
o Windowing
• Rescaling the image is primary the process of ____ which is the acquired data set
o Algebraically relabeling it
• Histogram analysis can fail to ID key landmarks when a bizarre data set results in an unexpected what?
o Histogram shape
• All of the following are general domains except what?
o Amplitude
• Sorting an image by the location of its pixels results in a _____
o Matrix
• Point area in global operations are all sub-cats for what domain
o Spatial
• An example of an area of operation would be what?
o Zoom
• Whenever a displayed image is windowed, which of the following default processes is reapplied
o Graduation processing
• In dynamic range of the processing system is too limited, it is possible for what to occur when the displayed image is later windowed?
o Clipping
• From selective midpoint in various gray levels, lighter areas in the image are progressively darkened while darker areas are progressively lightened, this describes what?
o Dynamic range compression
• For the graduation processing curves developed by Fuji, the shape of a particular which a particular algebraic formula generates, is represented as the perimeter what?
o GT
• Noise in the image caused by electronic malfunctions is normally periodic, occurring at regular intervals across the image, rather than random, such as quantum mottle. It’s best eliminated using what?
o Processing in a frequency domain
• A small core matrix of mathematical values which is passed through the image matrix, multiplying the value of each pixel sequentially by the numbers in it
o Kernel
• High-pass filtering only allows what to pass through?
o High frequency objects, small objects
• The math method by which the complex wave representing one line of digital image can be broken down into a set, the individual wavelengths that make it up is known as the what?
o Fourier method
• Dual energy subtraction takes average of what differences between soft tissues and bones
o Photoelectric
• What across the board adj. in radiographic techniques is suggested to allow for CR operation at a 400 speed class, reduced pt exposure, avoid mottle
o Increase 15% kVp
• If a dept. chooses to operate their CR/DR system at a 200 speed class, what general adj. in tech should be made form a 400 speed
o Double the technique
• How much overexposure is required before oversaturation occurs?
o 8-10 times more
- Which of the following states is true regarding CR
* Which is false?
TRUE = Digital processing is able to compensate for scatter
FALSE = Scatter always results in dark images
o For CR, as a general rule of thumb, what % of the receptor plat needs to be exposed to prevent errors
o At least thirty percent needs to exposure
o Which of the following has the least amount of effect on scatter?
o kVp
o Which of the following affects displayed image contrast?
o Windowing, gradation processing, rescaling
o The increased exposure latitude includes all of the following options except?
o Using low kVp
