Digital radiography and PACs (ch. 3)
Questions with Correct Answers
Aliasing - ANSWERSEffect caused by a fluctuating signal
Automatic rescaling - ANSWERSprocess by which images are produced with uniform
brightness and contrast, regardless of the amount of exposure
contrast manipulation - ANSWERSconversion of the digital image using contrast
enhancement parameters
critical frequency - ANSWERSthe frequency of a signal that exactly matches the
Nyquist frequency, resulting in a zero-amplitude signal caused by phase shifts
dose creep - ANSWERSIncreasing exposure factors to insure a quality radiograph
regardless of the excessive exposure to the patient
Histogram - ANSWERSGraphic representation of the signals from a X-ray exposure
Image sampling - ANSWERSamount of information gathered from pixel storage
Moire effect - ANSWERSImage noise pattern
Nyquist Theorem - ANSWERSa sampling law dictating that the data sampling frequency
must be at least twice the object's spatial frequency.
Postprocessing - ANSWERSManipulation of medical images after they have been
acquired through x-ray exposure, to improve image quality and diagnostic yield
Preprocessing - ANSWERSTakes place in the computer where the algorithms
determine the image histogram
Spatial frequency resolution - ANSWERSamount of detail or sharpness in a digital
image
What happens if the system fails to recognize the collimated edges of an image? -
ANSWERSHistogram analysis error
Horizontal axis of a histogram - ANSWERSPixel values
Vertical axis of a histogram - ANSWERSNumber of pixels
Questions with Correct Answers
Aliasing - ANSWERSEffect caused by a fluctuating signal
Automatic rescaling - ANSWERSprocess by which images are produced with uniform
brightness and contrast, regardless of the amount of exposure
contrast manipulation - ANSWERSconversion of the digital image using contrast
enhancement parameters
critical frequency - ANSWERSthe frequency of a signal that exactly matches the
Nyquist frequency, resulting in a zero-amplitude signal caused by phase shifts
dose creep - ANSWERSIncreasing exposure factors to insure a quality radiograph
regardless of the excessive exposure to the patient
Histogram - ANSWERSGraphic representation of the signals from a X-ray exposure
Image sampling - ANSWERSamount of information gathered from pixel storage
Moire effect - ANSWERSImage noise pattern
Nyquist Theorem - ANSWERSa sampling law dictating that the data sampling frequency
must be at least twice the object's spatial frequency.
Postprocessing - ANSWERSManipulation of medical images after they have been
acquired through x-ray exposure, to improve image quality and diagnostic yield
Preprocessing - ANSWERSTakes place in the computer where the algorithms
determine the image histogram
Spatial frequency resolution - ANSWERSamount of detail or sharpness in a digital
image
What happens if the system fails to recognize the collimated edges of an image? -
ANSWERSHistogram analysis error
Horizontal axis of a histogram - ANSWERSPixel values
Vertical axis of a histogram - ANSWERSNumber of pixels
