Ch. 12 Physics: 2 dimensional Imaging Flashcards
what are the two characteristics of sound that make 2D imaging challenging?
Sound travels in a straight line.
Sound beams must be narrow to optimize lateral resolution.
How do you overcome both of the difficulties in 2D imaging?
Sending multiple pulses to create a 2D image
What does the initial pulse do?
Narrow pulses are sent into the body
Receives reflections
Processes and stores data
What does the second pulse do?
Sent in a slightly different direction than the first
Processes data
What does the third pulse do?
Sent again, slightly different direction
What kind of transducer contains a single, circular, disc-shaped active element that is physically moved.
Mechanical transducer
What kind of image shape is created with a mechanical transducer?
fan or sector-shaped
How is fixed focus achieved?
Internal fixed focusing
External fixed focusing
In a mechanical transducer, what happens to when the active element is damaged?
Loss of the whole image
What are modern transducers called?
Arrays
Do arrays contain single or multiple active elements?
Multiple
the combination of the active element, wire, and system electronics
Channel
True or false:
Each single crystal or groups of crystals can be excited separately during transmission.
True
True or false:
Each element is connected by a wire to a group of electronic circuitry.
False
Each element is connected by a wire to its own electronic circuitry
What type of transducer arrays have the active elements arranged in a straight line?
Linear
What type of transducer arrays have the elements arranged as circular rings with a common center?
Annular
What type of transducer arrays have the elements arranged in a bowed or arched line? Also called a curved, or a curvilinear array.
Convex
How is a linear phased array steered focused?
Electronically
In a linear phased array, all elements are fired to create each sound pulse. Since all are fired at once, what is the degree angle?
90 degrees
10-nanosecond time differences between many wavelets to create a single unified sound beam that is directed to the side.
Phased delay
What does sloped mean?
Steered
the electronics within the system that create these patterns.
Beam former
the internal component within the system that determines the firing delay patterns for phased array systems.
Beam former
What determines the direction of the sound beam?
The slope of the electrical spike
the electrical signal creates a straight line
unfocused beam
the electrical signals create curved lines
focused beam
created by altering how curved the electricity signals are produced
Shallow vs deep focus
What does it mean when the sound beam is curved?
It’s focused
To create an image with multiple foci at different depths, the system must send _________ _________ _________down each scan line
Multiple sound beams
For 3 focal points, each scan line must have ___ separate pulses, one for each focal zone.
3
True or false:
All pulses will have different curvatures to their path.
True
The greatest curvature creates the beam with the most ________ focus.
Shallow
The beam with the least curved pattern, will create the _______ focus.
Deepest
What kind of beams outer spikes are fired first, creating the concave curved appearance?
focused beams
What kind of beam center spike is fired first, creating a D-shaped, convex appearance?
unfocused beams
Which beam shape has no clinical significance or application?
focused
unfocused
unfocused
What kind of focusing occurs during reception?
Dynamic Receive Focusing
This automatic focusing is performed by the system and cannot be adjusted by the sonographer.
Dynamic receive focusing
During __________, when reflected sound arrives at the transducer, multiple neighboring elements in the probe are excited.
Reception
The ________ ________ used during receive focusing depend on the depth at which the reflection was created.
optimal delays
True or false:
Dynamic receive focusing is applied to all depths along the scan line
true
Which phased array active elements appear disc-like?
Annular phased array
True or false:
in annular phased array transducers, the disc has multiple ring-shaped elements with a common center.
true
True or false:
in annular phased array, beam steering is available.
False
Mechanical steering creates the two-dimensional image as sound beams are transmitted in different directions by a motor that physically moves the ringed-element
a crystals diameter is _______ related to its focus depth.
directly
in annular phased array, The inner crystal (the smallest) will create the _________ focus.
shallowest
in annular phased array, The focus depths will continue to _________ as the crystal’s diameter increases from the center.
deepen
When one ring of an annular array transducer malfunctions, what happens to the image?
Only a portion of the image is lost
Linear Sequential arrays have a much larger footprint and create _______ images.
rectangular images
How many rectangular-shaped strips of PZT material arranged side by side in linear sequential arrays?
120- 250
In linear sequential array, damaged crystals create a loss of image in a _______ line.
vertical
True or false:
The rectangular shaped image is never wider than the footprint of the transducer
True
A rectangular grey
scale image is produced
with a ___________
linear sequential
array transducer.
True or false:
curved transducers are very similar to linear array transducers.
True
In a convex array, the pulses travel ……
in different directions as they radiate out
for this transducer the image is described as a blunted sector-shaped.
convex
In a convex transducer, damaged crystals create a __________ loss of image in the line where the damaged crystal is defective.
vertical
Combines linear sequential and linear phased array technologies
Vector arrays
Image shape is trapezoid for this transducer array.
Vector arrays
