Chapter 12 Flashcards
Mechanical Transducer
Not in use today
Contains a single, circular, disc shaped element
image is sector (fan or pie) shaped
small footprint
Focusing was mechanical
Crystal damage lost entire image
Footprint
face of probe that comes into contact with the skin
a channel
Each element is connected by a wire to its own electronic circuitry
Arrays
contain multiple active elements
A single slab of PZT is cut into many pieces or elements
Array Transducers
Linear: Active elements are arranged in a straight line
Annular: Elements are arranged as circular rings of PZT
Convex, Curved or Curvilinear: Elements are arranged in a curved, bowed, or arched line
Linear Phased Array Transducer (cardiac sector probes)
Compact with small (~1 cm) rectangular footprint;
Elements are very thin
100-300 narrow rectangular elements
beam is focused electronically
phasing
All crystals are stimulated to create each beam
Linear Phased Array and Multi-focusing
To create an image with multiple foci at different depths, the system must send multiple sound beams down each scan line
Dynamic Receive Focusing
A more accurate image can be created when the ultrasound receiver introduces time delays to some of the electrical signals during reception
(performed automatically)
Annular Phased Array Transducer
Elements are rings of PZT
Mechanical steering
Small footprint
Fan or pie shaped
Electronic focusing
Horizontal band of dropout
Linear Sequential Array Transducer
Large footprint
rectangular image
Used in vascular imaging
120-250 strips of PZT
Electronic steering
vertical band of dropout
sequencing
Elements are stimulated in groups simultaneously to send the pulse straight ahead
Then the next group of crystals is stimulated to direct the next sound beam straight ahead
Convex, Curved, or Curvilinear Sequential Array Transducers
120-250 strips of PZT
used for Abdominal or OBGYn
Large footprint
beams steered electronically with sequencing
top of sector wide as footprint
electronically focused
vertical band of dropout
Vector Array Transducers
120-250 strips of PZT
medium footprint
beam steering electronically sequenced
electronic focusing
vertical band of dropout
trapezoid image
vascular and cardiac image
Image resolution
Shallow to deep = longitudinal resolution
Side to side = lateral resolution
Top to bottom (height) of the imaging plane = slice thickness/elevational resolution
