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