Ch 15 Flashcards
Bistable
2 shades; black and white High Contrast
Gray Scale
Multiple levels of gray Low Contrast
Analog
“real world” numbers
unlimited # of choices
continuous values
Digital
“computer” numbers
limited choices
discrete values
Contrast
determines the range of brilliance within the displayed image
Brightness
determines the range of the displayed image
Scan convertor
translates the information from the spoke format into the video format
Spatial resolution
image detail
Disadvantages of analog scan convertors
image fade
image flicker
instability
deterioration
Advantages of digital scan convertors
Uniformity
Stability
Durability
Speed
Accuracy
Pixel
smallest building block of a digital picture
Pixel Density
Number of picture elements per inch
Low Pixel Density
pixels per inch
size of pixels
detail of image
spatial resolution
few pixels per inch
larger pixels
less detailed image
lower spatial resolution
High Pixel Density
pixels per inch
size of pixels
detail of image
spatial resolution
many pixels per inch
smaller pixels
more detailed image
higher spatial resolution
Bit
smallest amount of computer memory
Byte
group of eight bits of computer memory
Word
computer memory consists of two bytes or 16 bits
Contrast Resolution
gray shades
Fewer Bits per Pixel
shades of gray
contrast resolution
fewer shades of gray
degraded contrast resolution
More Bits per Pixel
shades of gray
contrast resolution
more shades of gray
improved contrast resolution
Calculating the shades of gray
2^ number of bits
Pixels vs Bits
Pixel
image element
image detail
spatial resolution
Pixels vs Bits
Bits
computer memory
gray shades
contrast resolution
Analog to digital converter
Analog -> analog to digital converter -> Digital memory -> digital to analog converter -> Analog
Preprocessing
manipulating before storage in the scan convertor
TGC , log Compression , write magnification, persistence, spatial compounding, edge enhancement, fill-in interpolation
Postprocessing
manipulating after storage in the scan convertor
any change after freeze frame, black/white inversion, read magnification, contrast variation, 3-D rendering
Read Magnification
uses old data
postprocessing
larger pixel size
same # of pixels as in the original ROI
unchanged spatial resolution
unchanged temporal resolution
Write Magnification
acquires new data
preprocessing
identical pixel size
more pixels that in the original ROI
improves spatial resolution
may improves temporal resolution
Coded Excitation
method of improving image quality
creates long sound pulses containing a wide range of frequencies
occurs in pulser
Advantages of Coded Excitation
higher signal to noise ratio
improved axial resolution
improved spatial resolution
improved contrast resolution
deeper penetration
Spatial Compounding
method of using different angles to produce a single image
reduce speckle and shadowing
used with electrical steering / phased array only
Frequency Compounding
reduce speckle and noise artifact
reflected sound wave is divided into subbands
Edge Enhancement
makes image look sharper
works by increasing image contrast
creates sublte bright and dark highlights around edges to make them look more defined
Temporal Compounding or Persistence
makes image smoother
“super impose”
Fill-in Interpolation
predicts what information lies between the gaps and improves spatial resolution
preprocessing
Elastography
measure how dense something is and have mechanical properties
PACS
Picture Archiving and Communications System
Stored digitally
DICOM
Digital Imaging and Computers in Medicine
set of rules, or protocols, that allows imaging system to share info on a network
assure’s communicatoin for future devices
Recording and Archiving Techniques: Paper Media Examples
charts from pen writers
Recording and Archiving Techniques: Paper Media Advantages
portability does not require a device to read
Recording and Archiving Techniques: Paper Media Disadvantages
bulky, hard to store difficult to make copies cant display dynamic images
Recording and Archiving Techniques: Magnetic Media Examples
computer discs computer memory magnetic tape video tape
Recording and Archiving Techniques: Magnetic Media Advantages
able to store large amounts of info efficiently can store and play dynamic can record color
Recording and Archiving Techniques: Magnetic Media Disadvantages
can be erased by strong magnetic fields
Recording and Archiving Techniques: Chemically Mediated Photographs Examples
photographs flat films multiformat camera film
Recording and Archiving Techniques: Chemically Mediated Photographs Advantages
High resolution accepted in the medical community can produce color images
Recording and Archiving Techniques: Chemically Mediated Photographs Disadvantages
bulky, difficult to store and retrieve requires chemical processing artifacts can arise from dirt pr chemical contamination
Recording and Archiving Techniques: Optical Media Examples
laser discs compact discs
Recording and Archiving Techniques: Optical Media Advantages
store huge amounts of data inexpensive not erased by exposure to magnetic field
Recording and Archiving Techniques: Optical Media Disadvantages
requires a display system no standardized format for image display and storage
