EXAM #6 Tutor Questions Flashcards by Casey Myles Jones

• Overall resolution for imaging is measured as physicists as

MTF

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• If in the remnant beam signal, what can reduce subject contrast and gray scale

Scatter

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• How do you measure spatial frequencies

LP/mm

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• Mathematically, the ratio of an images recorded contrast to the real subject contrast defines what

o MTF, closest to one as possible

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• Which of the following is NOT a variable affecting sub contrast in remnant beam

o Focal spot

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• For the computer to process an image, analog to digital is composed by a device called

o Analog to digital converter

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• In general, digital imaging terms, brightness is what?

o Window level

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• 1000x1000 matrix? How many pixels?

o 1mil pixels

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• Compared to Work station, display stations can typically have

o Less resolution

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• The selection of a narrow window width

o Increase contrast

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• Dead pixels in the image is caused by failure of dead DELS

o Interpolation

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• Flat field uniform corrections because of all the following except for what?

o Data clipping

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• List of pixel values that make up a histogram, it’s called a permanent what?

o LUT

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• A sub matrix that is passed over the original, executing a mathematical function is called what?

o Kernel

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• Pattern recognition software is used for what?

o Segmentation

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• Normalization is best described as the computer attempt to

o Make digital image look like a film image prior to any post processing

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• Which of the following can a comp processing not do?

o Cannot change the pixel count

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• Histogram correction errors are

o Not necessarily related to the radiographic technique used

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• Histogram analysis failure is less common with DR, than CR, because DR algos include what

o Only the exposed DELS

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• Histogram is the result when a digital image is sorted by

o Values contained by pixel

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• Low freqs represent what?

o Large objects

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• 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)

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• For all digital image systems, a restriction for lower limit for exposure

o Mottle

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• Just as in conventional radiography, the what must have a high SNR

o Remnant beam

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• 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