digital quality worksheet

digital images have ______ spatial resolution and ______ contrast resolution

inferior

superior

what type of error occurs when the computer cannot detect the borders of the IR exposed

histogram error

small pixels result in ________ spatial resolution

increased

a low exposure to the IR will result in what type of digital artifact

quantum mottle

this controls the number of shades of gray available to a digital imaging system

bit depth

a system that displays a greater number of shades of gray has better ______ resolution

contrast

window width controls

contrast or gray scale

window level controls

brightness

digital receptors are more/less sensitive to scatter

more

the adjusting of the image by the computer program to present an image with predetermined brightness is called

automatic rescaling

an expression of how well the signal of a digital system is preserved in animage compared to the amount of noise present

signal to noise ratio

how well subject contrast of a body part is represented in the image

MTF

how efficiently a system converts x-ray input into a useful output signal (speed class)

DQE

what type of error most commonly results in the need to repeat an image with digital

positioning errors

measure of luminance of a soft copy monitor expressed in candela per sq meter

brightness

the measurement from the center of one pixel to the center of the next determines

pixel pitch

this states the scan frequency must be 2x the bandwidth for a quality image

Nyquist theorem

picture element is a

pixel

how often data is aquire3d from the detector

sampling frequency

T or F: kVp is no longer important in determining beam quality with full field digital systems

false

cassette-less digital systems use _______ as an indicator of exposure to measure actual energy absorbed vs radiation exposure

DAP

the sampling frequency of a digital system with 500 pixels should be

1,000 lp/mm

how many shades of gray are available using a system with a bit depth of 14

2¹⁴ = 16,384

an extremely overexposed IR will display poor

contrast

the higher the sampling frequency the __________ the spatial resolution

better

what is the pixel size with a matrix of 1024 and a FOV of 24cm

240mm / 1024 = 0.23 mm

with digital imaging what has the greatest control over image contrast

the look up table

a digital system’s response to exposure is

linear

what type of grid frequency is recommended for use with digital systems

high

T or F: mAs no longer controls beam quantity with digital imaging

false

this determines the exposure indicator value

histogram analysis