Digital Imaging Review Flashcards
What term describes the smallest unit of info within a digital image?
picture element (Pixel)
What term describes the component of digital radiography receptors responsible for capturing the radiation signal transmitted through the patient
Detector Element (DEL)
What term describes the light-emitting components within display monitors
picture element (pixel)
When the matrix size of a digital image increases, the size of the individual pixels (increases/decreases)
decreases
When the matrix size of a digital image increases, the size of the pixels within the image (increase/decrease)
decrease
As the matrix size of a digital image increases, the pixel size (increases/decreases)
decreases
When the matrix size of a digital image decreases, the size of the pixels within the image (increase/decrease)
increases
How does increased matrix size affect the spatial resolution of a digital image?
increases spatial resolution
How does decreased matrix size affect the spatial resolution of a digital image?
decreases spatial resolution
Which would be the matrix size associated with the highest spatial resolution?
256x256
1024x1024
2048x2048
2048 x 2048
What makes up the digital matrix of the image file?
pixels
Within digital radiography image matrix, 1024 x 1024 refers to what?
number of pixels in the matrix
matrix size
What radiographic matrix would create an image with the smallest pixels?
512x512
1024x1024
2048x2048
2048 x 2048
What variables of a matrix affect spatial resolution?
pixel size
matrix size
A larger matrix size would create a more (clear/pixelated) image
clear
Which spatial frequency would produce the greatest spatial resolution?
1.12 lp/mm
4.15 lp/mm
6.30 lp/mm
6.30 lp/mm
How to calculate pixel size…
pixel size = FOV / Matrix size
FOV (field of view)
How to calculate spatial frequency?
SF = 1 / (2 x pixel size)
Define dynamic range in radiography?
range of exposures that can be captured by an image receptor (IR)
Exposure latitude is defined as…
range of exposure that produces quality images at an appropriate patient dose
The specifications for an xray imaging system indicate that the detector can capture exposure values from 0.1 microgray to 1000 microgray. This quality of the system is called…
dynamic range
Consider an xray exposure that results in a receptor exposure of 0.001 microgray, the resulting image is expected to display what? and why?
quantum mottle
detector has not received enough information to create a quality image
An xray exposure above the highest level of the exposure latitude may result in an image error called…
saturation artifact
Define exposure latitude
ability to produce radiographs at a wide range of technical factors
A radiographer acquires an optimal image of the wrist using 60 kvp and 2.5 mAs. Acquiring the same projection of 72 kvp and 5 mAs will result in what?
excessive patient dose
Consider this scenario: One radiographer acquires an image of the chest using 100 kvp and 2 mAs. A different tech acquires an image of the chest of the same patient using 120 kvp and 2.5 mas. Both exposures result in EI that were acceptable. This is an example of…
exposure latitude
What characteristics are present on an xray that was taken using a too low exposure setting?
quantum mottle
grainy
Define bit depth
total number of brightness levels that can be produced by the digital system
How many shades of gray can be displayed on a 8-bit digital radiography system?
256 shades
Calculate shades of gray from bit depth
2^n
where n = bit depth
Higher bit depth allows for (greater/less) amount of anatomic information on an image
greater
quantization is a digital radiography process through which receptor reading are…
converted to specific digital values
Higher contrast resolution means (more/less) shades of gray
more
during digital image formation and processing, quantization takes place where
analog to digital converter (ADC)
What is the smallest exposure diference that can be detected and displayed by the imaging system?
contrast resolution
What factor influence the grayscale of a digital radiograph
bit depth
As window level increases, brightness _______
increases
The range of exposures a digital system can retain and use to create the image is the _________
dynamic range
Quantum mottle on a digital image is caused by insufficient ___ ____
photon quantity
T/F If a digital image is overexposed it must always be repeated.
false
As you narrow the window width, you will create a _____ (longer/shorter) scale of contrast.
shorter
Grayscale on a digital system is another way of describing the ____
scale of contrast
number of pixels to create an image is the _____
matrix size
T/F The use of a digital imaging system affects the process that creates size and shape distortion.
False
T/F The digital imaging system is more sensitive to artifact material.
True
A larger matrix will have ____ (smaller/larger) pixels, meaning the pixel pitch is (smaller, larger)
smaller, smaller
A wide window width on an image will make it look more black/white or gray/white
black/white
The ratio of radiation exposure to noise captured on an image is _____
signal to noise ratio
T/F Monitor quality will affect spatial resolution of an image
true
The relationship between spatial frequency and modulation transfer function is (indirect/direct)
indirect
The ____ determines the amount of gray shades the system is able to display on the digital image
bit depth
Pixel pitch, pixel size, and pixel density all have an affect on _______
spatial resolution
What is “signal” referring to or describing?
useful information captured from the remnant beam
Patient’s actual anatomy
Blotchy appearance caused by insufficient number of photons reaching the image receptor is known as ….. (3)
quantum noise
quantum mottle
photon starvation
What would reduce system noise?
proper upkeep/maintenance of equipment
What type of noise cannot be reduced and is always present/constant?
ambient noise
Increasing the kvp would (increase/decrease) the signal and (increase/decrease) the scatter reaching the IR.
increase, increase
Photons that add information but do not represent the anatomic structures are considered….
scatter radiation
When using a grid is it preferred to increase kvp or mas
mas
