Digital Imaging processing & characteristics

with digital imaging, the analogue xray signal is sampled and converted to the

numbers

the exposure intensities that will be included in the image construction

value of interest (VOI)

what is the word used for a picture element

pixel

the smaller the _____ the better the image ______

pixel, resolution

what controls the number of shades of gray available to the image

bit depth

the number of shades of gray available to an image controls image 

contrast 

which bit depth offers more shade of gray

16

how many shades of gray are available to the image with a bit depth of 16 

65,536

the larger the matrix the ____ the spacial resolution

better

calculate the pixel size if the FOV is 40 cm and the matrix size is 512 

0.78 mm 

what is the pixel size with a FOV of 360 mm and a matrix of 1024.

0.35 mm

what term is used to describe the amount of exposure recieved by the image receptor

exposure indicators

when the fuji “S” number is high, the image is

underexposed

the mathematical formula used by the computer to perform functions

algorithms 

an image that is under exposed may exhibit an excessive amount of 

noise/mottle 

the tech can adjust image brightness using the _____ _____ controls 

window level 

the tech can adjust image contrast using the ____ ____ controls

window width

image resolution is very dependent on ___ size

pixel 

spatial resolution is a term that is used to describe image 

detail/sharpness 

a digital system ability to demonstrate subtle differences in shades of gray describes

contrast resolution

when sampling frequency is too low, this mirroring error occurs on the image 

aliasing

one of the greatest advantages of digital imaging is superior

contrast resolution

high pass filtering

edge enhancement

low pass filtering

smoothing

what term describes the ratio of recorded contrast to the real contrast of object 

MTF

the amount of signal vs noise in a digital image is expressed as 

signal to noise ratio 

the term used when not enough photons are available 

photon starvation/quantum mottle 

image _____ is caused by electronic interference

snow

define dynamic range

range of exposure intensities that IR can repsond to and use to acquire image data 

define exposure latitude 

range of exposure values an IR is able to produce 

the overall efficiency with which a detector converts incoming xray exposure to useful signal is the definition of what

detective quantum efficiency

graphic display of pixel intensities

histogram

contains the data that has the standard contrast, speed and latitude for a particular exam

look up table

when the computer adjusts the pixel intensities to more closely match those of the average histogram stored in the LUT this is 

rescaling 

spatial resolution is measured in 

lp/mm

the frequency with which the data is read out from the detector, defines

sampling frequency 

list 4 things that contribute to resolution with digital imaging 

• pixel size

• pixel pitch

• focal spot size

• sampling frequency

true or false: digital systems are less responsive to scatter than film/screen

false

true or false: overall, digital systems exhibit better spatial resolution than film/screen

false 

better spatial resolution HIGHER/LOWER sampling frequency, and LARGER/SMALLER pixels

higher and smaller

type of data drop that involves area/regions

detector saturation

the center of one pixel to the center of another is what

pixel pitch

the signal must be sampled a minimum of ____ times to create a quality image

2

which IR type has the highest DQE

indirect capture 

which IR type results in the lowest patient dose

indirect capture

the minimum resolution of a primary diagnostic reading monitor

2,000

digital systems have a ____ characteristic response to exposure

linear 

_____ ____ assumes images are taken in accordance with department protocols/procedures

diagnostic yielding

______ _____ assumes protocols/ standards are met, and the images are a true representation of patient and anatomy

diagnostic efficicay

true of false: the tech no longer has to use right and left markers because they can annotate post exposure

false