2 Ch 12: Two-Dimensional Imaging Flashcards
The mechanical transducer contains a ___ active element.
circular, disc-shaped
The mechanical transducer contains an active element that is phsically ___.
moved.
How many active elements does a mechnical transducer have?
one
What shape image is created by a mechanical transducer?
fan or sector-shaped
How is the beam steered with a mechanical transducer?
with a motor; mechanical steering
T/F? Mechanical transducers have a fixed focal depth.
true
Name two methods of fixed focusing.
internal - curved active element
external - curved acoustic element
What happens if the crystal gets damaged in a mechanical transducer?
The entire image is lost.
An ___ contains multiple active elements.
array
An array contains…
multiple active elements.
A ___ is the combination of the active element, wire and system electronics.
channel
A channel is the combination of…
the active element, wire, and system electronics.
How are the active element channels arranged in a linear phased array?
in a straight line
How are the active element channels arranged in an annular phased array?
as circular rings with a common center
How are the active element channels arranged in a convex phased array?
in a a bowed or arched line
How many active elements does a linear phased array have?
100-300
What shape image is created by a linear phased array transducer?
fan or sector-shaped
How is the beam steered with a linear phased array transducer?
a process called phasing; electronic steering
T/F? Linear phased array transducers have a fixed focal depth.
FALSE: The phased array system has controls that allow the sonographer to modify the depth and amount of focusing of the sound beam.
T/F? Phased array always means adjustable or multi-focus.
true
Modern phased array systems can transmit ___ beams down the ___ scan line, each with a ___ focal depth.
multiple, same, different
What happens if the crystal gets damaged in a phased array transducer?
inconsistent or erratic beam steering and focusing
How many elements in a phased array probe are used to create a single sound pulse?
ALL of them.
In a phased array system, how does the pattern of electrical spikes from the u/s system steer the sound beam in different directions?
The angle of the electrical spikes determines the angle of the beam.
The time differences between the electrical spikes firing are called…
phase delays.
The sound beam in a phased array tranducer is steered if…
the spike line has a slope.
When the spike line in a phased array tranducer is a straight line…
an unfocused sound beam is created.
The electronics within the u/s system that create electrical spike patterns is called…
the beam former.
How does the pattern of electrical spikes from the beam former focus the sound beam during transmission?
It fires the outer crystals before the inner crystals to create a curved pattern.
When the spike line in a phased array transducer is a curved line…
a focused sound beam is created.