Display Imaging, 2D, and Real Time Imaging Flashcards
What is an array?
A modern transducer that contains multiple active elements
What makes a transducer linear?
If the active elements are arranged in a straight line
What makes a transducer curved?
If the active elements are arranged in an arched or bowed line
What is a sequential array?
When many large elements are arranged in a line side by side
What is a phased array?
When many smaller elements are electronically steered in different directions
What is the shape of an image produced by a linear sequential array?
A rectangular image
What is the shape of an image produced by a linear phased array?
A fan or sector shaped image
What adjustments to the sound beam are made possible with the phased array?
Adjustable focus
An electronic slope that steers the beam and an electronic curve that focuses the beam during transmission
What shape of image is created with a curved sequentual array?
A blunted sector image
What shape of image is created by a curved phased array?
A small footprint with more divergence in the far field
How are crystals arranged in an annular array?
In a disc like shape
How is a 2D image generated?
System sends a narrow pulse into the body. receives the reflections, and processes and stores the data
Another beam is sent in a slightly different direction, and the process continues
For mechanical scanning what number and shape of crystal is used?
One crystal in a circular disc-like shape
For mechanical scanning, how is the steering and focusing achieved?
Steering - by sound beams being emitted as the crystal is rotated with a motor
Fixed focal depth with internal or external focusing
What is an image shape created by mechanical scanning?
A fan or sector shape
What happens if there is a defective crystal?
The entire image is lost
What is a transducer array?
A collection of active elements in a signal transducer
What are the pieces of PZT in an array called?
Elements
What is a channel in an array transducer?
The combination of the active element, wire, and system electronics
What is a 3D or multidimensional array?
A volume image created by a 2D array with thousands of elements arranged in a checkerboard pattern
In A mode what is displayed on the x and y axes?
X axis is reflector depth
Y axis is reflection amplitude
What is B mode?
Brightness mode
Scans that are static images
Appears as a line of dots with varying brightness
The basis for gray-scale imaging
In B mode what is displayed with the x and z axes?
X axis is reflector depth
Z mode is amplitude info
What is M mode?
Motion mode
Indicates a reflector that is moving closer or farther away from the transducer
What do the x and y axes display in M mode?
X axis displays the time
Y axis displays the reflector depth
What is frame rate?
The number of frames created each second
What determines frame rate?
The sound’s speed in the medium
The depth of imaging
What units do we use for frame rate?
Images/second
What units are used to measure frame rate?
Hertz
What is temporal resolution?
The ability to precisely position moving structures from instant to instant
How is frame rate related to temporal resolution?
Directly
Temporal resolution is determined by frame rate
How are frame time and frame rate related?
Inversely and reciprocals
Frame Rate x Frame Time = 1
Which ultrasound system settings determine frame rate?
Imaging depth
Number of pulses per frame
How does imaging depth affect temporal resolution?
Inversely
A shallow depth has better temporal resolution
A deeper depth has worse temporal resolution
How is the number of pulses per image related to frame rate?
Inversely
The fewer pulses, the higher the frame rate
The more pulses, the lower the frame rate
What three factors affect the number of pulses per image?
Number of focal points
Sector size
Line density
What type of resolution is improved by using multiple focal zones?
Lateral resolution
What type of resolution is degraded when multiple focal zones are used?
Temporal resolution
How is sector width related to frame rate?
Narrow sector width has a higher frame rate
Wide sector width has a lower frame rate
How is line density related to frame rate?
Low line density has a higher frame rate
High line density has a lower frame rate
What is the benefit of scanning with high line density?
The gaps between lines are smaller, increasing the accuracy of each image
What kind of resolution is improved with high line density?
Spatial (detail) resolution
