Ch.12 Two-Dimensional Imaging Flashcards
Mechanical Transducer
contains a single, circular, disc-shaped active element that is physically moved. This movement creates a scan plane
Mechanical Transducer
Crystals: # and shape
can have only 1 active element ; coin shape
What image shape do mechanical transducers make?
fan or sector shaped; crystal is physically moved. (Car wind shield wiper sweep)
Mechanical Transducer:
Beam steering
Beam focusing
Mechanical steering
-2D image is built up by rotating the crystal with a motor.
Fixed focal depth called:
conventional, mechanical, or fixed focusing
What are the two methods of fixed focusing?
Internal focusing: the use of a curved active element.
External focusing: the use of an acoustic lens.
Focusing occurs in what planes?
Both the horizontal and vertical planes bc of the hour glass shape of the sound beam.
Whenever the crystal in any single crystal transducer breaks, the ______ image is ______ .
entire
lost
Transducer Arrays
contain multiple active elements.
-comprise a single slab of PZT cut into a collection of separate pieces called elements
Each active element is connected by a _____ to its own _______ _______ in the ultrasound system.
wire
electric circuitry
Channel
is the combination of the active element, wire, and system electronics
Each element has its own electric connection, the system can excite a ______ or _______ _________ in various ways during ___________ .
single or multiple elements
transmission
During reception, each individual crystal produces a ________ ________ ________ that returns to the system’s receiver.
small electronic signal
What are the types of array transducers?
Linear
Annular
Convex
Linear transducer arrangement
active elements are arranged in a straight line
Annular transducer arrangement
elements are arranged as circular rings with a common center
Convex transducer arrangement
Active elements are arranged in a bowed or arched line. The transducer may also be called a curved, or curvilinear array.
Phasing
is when the beam is steered and focused using an electrical technique
Linear Phased Array Transducers is a
small square or rectangular transducer about 1 cm on each side that has no moving parts. (carotid one)
Linear Phased Array:
Crystal # & Shape
as many as 100 to 300 elements arranged along the face of the probe.
Placed side by side, each element is rectangular and narrow with a width of 1/4th to 1/2 of the sound’s wavelength.
Linear Phased Array:
image shape
fan or sector-shaped similar to mechanical transducer
Linear Phased Array:
Beam Steering
2D image is built up with an electronic steering process called phasing ; no moving parts
(wind shield wiper sweep motion)
Phased array ALWAYS means:
adjustable or multi-focus
Linear Phased Array:
Beam Focusing
focused electronically
Unlike mechanical transducers with a single fixed focus, the phased array system has controls that allow the sonographer to ______ the ______ and amount of ________ of the sound beam.
modify
depth
focusing