Transducers part 2

Linear Switched or sequential arrays # of crystals and shape

BIG transducers with approx 200 rectangular shaped elements arranged in a line

how many elements fire

a few elements (3-10) but not all fire at the SAME time to create a narrow directional beam. IMPROVES LATERAL RESOLUTION

Steering with linear switched

NO steering, pulses sent down parallel lines, scan lines are parallel and remain equally spaced at all depths

what type of focusing for sequential

fixed focusing- lens (external) or curved crystal (internal)

image shape of sequential

rectangular image shape no wider than the transducer

defective crystal with sequential

dropout extending from superficial to deep (creates a line dropout from top top to bottom)

phased arrays

adjustable focus or multi focus achieved electronically

#of crystals and shape for phased

approx 200 rectangular shaped elements arranged in a line

steering and focusing for phased

a collection of electric pulses delivered to ALL the transducer’s elements in various patterns for each pulse. Focusing and steering are ELECTRONIC

electronic signals excite what

all of the transducer elements to create each sound pulse

when does the phasing patterns focus and steer the sound beam

during transmission

image shape of phased array

fan or sector-shaped

size of phased array transducer

SMALL

defective crystals in phased array

if one element malfunctions, the steering and focusing become erratic

electronic slope creates what

beam steering

electronic curvature creates what

beam transmit focusing

beam former

system creating these electronic patterns (slopes, and curves) delays are approx 10nanoseconds

dynamic receive focusing

phased delays during RECEPTION providing focusing at MANY DEPTHS during reception (focusing typically occurs during transmission)

Annular phased array

concentric rings cut from the same circular slap of PZT. (bulls eye)

crystals for annular & #

small number of ring-shaped (donut) elements. concentric circles, 5

strategy for annular

selected focal zones, use INNER crystals for SHALLOW regions and OUTER crystals for DEEP regions.

smaller vs larger diameter

small diameter rings=shallow focus but diverge rapidly

large diameter rings=deep focal length

Image shape of annular and what resolution does it degrade

fan or sector shaped, degrades temporal resolution (lower frame rate)

Focusing for annular phased

FIXED achieved electronically. (unlike other phased array)multi-focusing provides electronic focusing in all planes at all depths, a core sample, OPTIMAL LATERAL RESOLUTION

annular phased arrays steering

is performed mechanically (UNLIKE other PHASED array transducers) CARDIAC

defective crystal for annular phased arrays

causes a horizontal (side to side) band of dropout

convex or curved arrays

PZT crystals arranged in a curve to provide a NATURAL sector. can be sequential or phased array (like a linear arrray)

crystals and # for convex

approx 200 (100-500) rectangular shaped elements.

Image shape of convex

blunted sector, fan shaped (bit taken out of the top)

Large transducer

convex sequential arrays place a large acoustic footprint on the patient.

small transducer

typically a convex phased array

multidimensional arrays

2-D arrays create 3D or 4D (real time 3D). Measures volumes of structures such as CYSTS.

**Use electrical delays to optimize focus in the LATERAL and ELEVATIONAL plane

2D arrays number of elements

same number of elements in the up and down and side to side directions (thousands of elements)

vector arrays

trapezoidal imaging- combine linear sequential and linear phased array technologies.

Image shape of vector arrays

trapezoidal, basically a sector with a flat top that does NOT come to a point

focal points for vector

multiple focal points appear in the image, produced by a phased array transducer

what is 4D imaging

a 3D imaging captured in real time

voxels

volume elements (makes up 3D imaging)

pedof transducer imaging shape, crystal shape & #

no image created, semi circle, 2

damaged PZT of pedof

no signal can be sent or received

steering, focus and common uses for pedof

manual, fixed (external or internal), vascular

what describes a hockey stick transducer

has a small footprint and is used for high frequency imaging superificial structures USED IN MSK, for nerves