Physics Ch. 15 & 16 Flashcards
Composed of 2 shades, black and white
bistable images
Gray scale displays multiple
levels of brightness: white, black and gray
What are the two display user controls for video monitors
contrast, brightness
Determines range of brilliancies within displayed image
contrast
Bistable images are _____ contrast
high
Gray scale images are _____ contrast
low
Determines brilliance of the displayed image
brightness
Store information and display it
scan converter
Used in early days of two-dimensional imaging
analog scan converter
Used in modern day A-D imaging
digital scan converter
Can have an unlimited and continuous range of values
analog numbers
Discrete values
Digital numbers
Spatial resolution (imaging detail) of an analog scan converter is
excellent
Limitation of analog scan converter
image fade, image flicker, instability, deterioration
Use computer technology to convert images into numbers
digitizing (1s and 0s)
Advantages of digital scan converters
uniformity, stability, durability, speed, accuracy
Two important elements of digital scan converters
pixel, bit
Picture element, smallest building block of a digital picture
pixel
Number of pixels per inch
pixel density
Higher pixel density is achieved with
smaller pixels (more pixels per inch)
What improves with high pixel density and creates an image with greater detail
spatial resolution
Binary digit, smallest amount of computer memory, bistable
bit
Group of bits and a series of 0s and 1s, digital
binary number
A group of 8 bits of computer memory
byte
Computer memory that consists of 2 bytes
word
Many shades of gray have better
contrast resolution
How many shades of gray are displayed with 5 bits of memory
32
Converting information from analog to digital is advantageous because
digital information is far less susceptible to contamination
What is the 5 step process from analog to digital
- A-to-D converter, 2. preprocessing, 3. post processing, 4. D-to-A converter, 5. Analog form is displayed
Manipulation of image data BEFORE storage in the scan converter
pre processing
Can preprocessing be reversed
no
Manipulation of image data AFTER storage in the scan converter
post processing
Can post processing be reversed
yes
Sonographer can improve visualization of anatomic detail by enlarging a portion of an image to fill the enter screen
magnification/zoom
What are the 2 types of magnification
read, write
Which magnification occurs in postprocessing? Preprocessing?
read, write
In read, the number of pixels in the magnified image is _____ as the original
the same
In read, spatial resolution _______ because the number of pixels are _______
does not change, unchanged
In write, the number of pixels in the magnified image is ______ that that of the ______
greater than, original
In write, spatial resolution is ______ as there is an _____ number of pixels
improved, increased
Method of improving image quality. Developed within context of bioeffects
coded excitation
Creates very long pulses containing a wide range of frequencies
coded excitation
Coded excitation occurs in the
pulser
Advantages of coded excitation
- higher signal to noise ratio, 2. improved axial res, 3. improved spatial res, 4. improved contrast res, 5. deeper penetration
Method of using sonographic information from different imaging angles to produce a single image
spatial compounding
Is spatial compounding pre or post processing
pre
Reduces speckle and minimizes shadowing artifact
compound images
Do compound images improve spatial resolution? Temporal resolution?
yes, no
______ steering of the sound beam is used in compound imaging
electronic
Advanced technique that reduces speckle artifact and noise in the ultrasound images
frequency compounding
Preprocessing method that makes pictures look sharper
edge enhancement
Occurs in preprocessing, commonly known as persistence, processing technique that continues to display information from older images
temporal compounding, persistence, temporal averaging
Temporal compounding/persistence creates a _____ image with ______ noise, ______ signal to noise ratio and _____ image quality. It ______ temporal resolution
smoother, reduced, higher, improved, reduces
With sector shaped images, the scan lines separate at increasing depths. Gaps or missing information exists between the scan lines and this interprets it
fill-in interpolation
Fill-in interpolation ______ spatial resolution and is a form of _________
improves, pre processing
Images are related to mechanical properties of the tissue, will deform differently following the application of a force, stiffness data
elastography
Elastography ________ spatial resolution
does not improve
What does PACS stand for
picture archiving and communications system
Describes the digital ultrasound lab in which images and additional medical information are digitized and stored on a larger computer network
PACS
What does DICOM stand for
Digital Imaging and Computers in Medicine
Set of rules and protocols that allows imaging systems to share information on a network
DICOM
Method of describing the extent to which a signal can ary and still maintain accuracy
dynamic range
Units of dynamic range
dB
Comparison ratio between the largest and smallest signal that are measured accurately
dynamic range
As a general rule, the dynamic range of information _____ the more it is processed
decreases
Eliminates the potential errors when moving from on component to another
compression of dynamic range
If an image has high contrast, it has ____ shades of gray
few
Represents the level below which information will not be displayed
threshold
A _____ pixel density improves spatial resolution
high
Are the following procedures usually pre or post processing? Modifying a frozen image, read zoom, write zoom, adjusting brightness on the monitor, increasing the receiver gain
post, post, pre, post, pre
With frequency compounding, how many pulses are transmitted down each scan line
1
An uncompressed image signal within the receiver of an ultrasound system has a dynamic range of 110dB. The signal undergoes 40dB of compression. What is the dynamic range of the compressed signal?
70dB
An uncompressed signal has a dynamic range of 85dB. The signal undergoes 30dB of compression. What is the dynamic range of the compressed signal
55dB
After compression, a signal within the ultrasound system has a dynamic range of 70dB. The original signal was compressed by 40dB. What is the dynamic range of the original, uncompressed signal
110dB
A signal within a system’s receiver has a dynamic range of 60dB after compression. The original signal was compressed by 50dB. What is the dynamic range of the original, uncompressed signal
110dB
Narrow dynamic range has ____ contrast
high
Wide dynamic range has _____ contrast
low