LESSON 2.2 Flashcards
A digital image is made up of a two-dimensional array of numbers
consists of columns (M) and rows (N) that define small square regions called picture elements or pixels
MATRIX
The amount of body part or patient included in the image.
The larger the FOV, the more area is imaged
Field of View (FOV)
Is the smallest element in a digital image.
Pixel, or picture element
The size of the pixel is directly related to the amount of spatial resolution or detail in the image
PIXEL SIZE
The number of bits within a pixel
Most digital imaging systems have bit depths of 10 to 16, resulting in more shades of gray
Pixel Bit Depth
Refers to its appearance on the display monitor of the computer and is a function of the monitor’s ability to emit light through the surface of the display.
Brightness
The ability of the digital system to display subtle changes in the shade of gray.
Contrast Resolution
The ability of the imaging system to demonstrate small details of an object
Spatial Resolution
Image noise contributes no useful diagnostic information and serves only to detract from the quality of the image.
visible as brightness or density fluctuations on the image.
Quantum Noise
Ability to respond to varying levels of exposure, more tissue densities on the digital image are seen, giving the appearance of more detail.
Dynamic Range
The purpose of this class of processing is to generate an image that is more pleasing to the observer
Image Enhancement
The range of exposure diagnostic image values the image detector is able to produce.
Dependent on the image detector—the higher the dynamic range of the detector, the more values can be detected
Exposure Latitude
These processing operations “create images from other images or non-image data.
Image Synthesis
The purpose of image restoration is to improve the quality of images that have distortions or degradations
Image Restoration
When the frequencies of areas of interest are known, those frequencies can be amplified and other frequencies suppressed.
Also known as high-pass filtering and increases contrast and edge enhancement.
Edge enhancement
The purpose of image compression of digital images is to reduce the size of the image in order to decrease transmission time and reduce storage space.
Image Compression
Also known as low-pass filtering
Occurs by averaging each pixel’s frequency with surrounding pixel values to remove high-frequency noise.
The result is a reduction of noise and contrast.
Smoothing
The process of adding text to an image
Annotation
controls how bright or dark the screen image
window level
controls the ratio of black and white, or contrast
window width
Blacken out the white collimation borders, effectively eliminating veil glare
Background Removal or Shuttering
Results in a black appearance of bone and a white appearance of soft tissue
Image Inversion
Technique that can remove superimposed structures so that the anatomic area of interest becomes more visible.
Digital Subtraction
When anatomy or the area of interest is too large to fit on one cassette, multiple images can be “stitched” together using specialized software programs
Image Stitching
One of the most commonly used three-dimensional (3D) rendering techniques.
When doing a CT scan of a patient, thin axial slices can be acquired of a volume of tissue.
The slices can then be loaded into the MPR software, and a reconstruction in another plane can be produced
Multiplanar Reconstruction (MPR)
Used to visualize vessels
Maximum Intensity Projection (MIP)
used to visualize air-filled structures
Minimum Intensity Projection
Using a threshold of pixel intensity values, everything below the threshold will be removed, and everything above will be assigned a color and shown as a 3D object
Shaded Surface Display (SSD)
Similar to MIP but allows the user to assign colors based on the intensity of the tissue so that bone, contrast agent, and organs can be seen in different colors.
The technique uses a histogram-type graph to differentiate the various structures
Volume Rendering Technique (VRT)
