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25 Cards in this Set
- Front
- Back
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Echo Ranging Principle
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-1-D
-Uses reflection to determine object distance from the transducer. -Assumes velocity is constant and the path of reflected sound is direct. |
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Limitations of Linear Imaging
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Hard to visualize and interpret, everything looks similar, artifacts are common
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Most common artifacts of Linear Imaging
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Attenuation
Axial Resolution Beam width, focusing Speed Error (diff. than assumed) |
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Static
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Not moving, statue like
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Dynamic
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Actively moving
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How A-Mode is presented
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Echoes are presented as a static image on a static line (Absolutely static)
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Brightness of the B-Mode dot is related to....
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the amplitude of the reflected signal from the line of sight interrogated
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Height of an A-mode spike is related to.....
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the reflectivity of the interface
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The time delay between transmission and reception in A-mode denotes....
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depth of the interface
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Bi-Stable Image
(first B-mode pictures were recorded w/ CRT's that had an on/off mode) |
Strong signal=phosphorescent light it up
Weak echo=no signal *Recorded zero internal echoes |
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Position of a dot in B-Mode is related to....
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time delay between the transmission and reception, also denotes depth
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Analog Scan Converters
(early 70's) |
-New storage/display technology that had better detail.
-Introduced grey scale imaging. -Instable: changes due to weather/humidity -still use today to print pictures |
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Digital Scan Converters
(late 70's) |
-Inexpensive, reliable
-Used today to create and store images on hard drives |
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B-Mode Gated Mode
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2-D static B-Mode imaging
-useful for stationary images -requires "registration arm" |
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Registration Arm
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B-Mode transducer is mounted, position sensors provide the signals for the position of the generator
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Transmission Mode
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When you have two transducers, one sending and one receiving
*Only mode that detects a transmitted beam through a patient |
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A mode
B mode |
static graphical data
static gray scale |
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A and B mode overview
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Best for stationary images
Cannot use to produce an image for dynamic interfaces |
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Sonographic Interrogation
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The returning echo and processed signal shows every changing position of the interface
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M-Mode
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Creates an everchanging image from a line of sight
-First motion detection in DMS -Characterizes the movement of interfaces -First use was the mitral valve in cardiac US |
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M-Mode Limitations
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Must keep transducer moving.
The data set created is seperated in time, and you can't combine the sets because of differences in depth. Blurry picture is due to poor temporal resolution |
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M-Mode Benefits
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Simple
High axial resolution -motion in the lateral direction isn't shown -technique only samples line of sight -superior temporal resolution -real time imaging |
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Principles of real time 2-D imaging
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Real time images consists of multiple lines of sight by sweeping the beam in many directions
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Temporal Resolution
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Ability to resolve objects that are moving over time. A picture that doesn't blur has good....
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Spacial Resolution
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Combination of axial and lateral resolution. How well we can resolve a picture of a 2-D space.
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