Transducer Evolution

Question 1

mechanical transducers (thickness, shape, diameter)

Answer 1

thin
disk shaped
6-19mm diameter

Question 2

mechanical transducers had a ____ focal zone

Answer 2

fixed

Question 3

4 types of mechanical transducers

Answer 3

linear translation
wobbler
oscillating element
oscillating mirror

Question 4

linear translation

Answer 4

mechanical transducer

oldest
moved the crystal assembly along a track to “sweep” the tissue

Question 5

wobbler

Answer 5

mechanical transducer

motor rotated back and forth to obtain sector type image
fluid filled=risked bubble production

Question 6

oscillating element

Answer 6

mechanical transducer

crystals oscillate and mirror reflects to get linear FOV

Question 7

oscillating mirror

Answer 7

mechanical transducer

mirror moves with a stationary element to get a linear FOV

Question 8

rotating wheel probes

Answer 8

several crystals spin and only pulse when the element passes the FOV

Question 9

FOV

Answer 9

field of view

Question 10

annular array was important why (hat stayed the same and what changed)

Answer 10

probe still mechanically steered but the ability to dynamically change the focus was now possible

Question 11

the annular array uses what shape of crystal and what was the purpose of the shape

Answer 11

concentric discs ( one crystal cut into rings)
by changing the disc fired, you change the diameter= varies the focal depth

Question 12

the diameter of the crystal changes the ______

Answer 12

focal depth

Question 13

grating lobes (annular array)

Answer 13

low energy beams that radiate away from the main axis and contribute to artifacts in the image

Question 14

what is phasing

Answer 14

phasing uses nanosecond time delays to change when the voltage excites the crystal

Question 15

what is the purpose of phasing

Answer 15

to control the beam (Huygen’s principle) and allow for beam focusing and steering

Question 16

focusing and steering are accomplished with the _____ of the voltages to the crystal in the _____ probes

Answer 16

phasing
electronic array

Question 17

what is another term for describing steering the beam

Answer 17

Vector scanning

Question 18

_____ of waves hit with a voltage at different times causes steering of the beam

Answer 18

interferance

Question 19

the steered beam goes in the _______ (opposite or same) direction as the delay

Answer 19

opposite (hit right crystal first beam is steered to the left)

delay /
/
beam \
direction \

Question 20

sector phased array: all crystals are fired at ______ time to steer the beam across the face of the probe

Answer 20

nearly the same

Question 21

the sector FOV can be as large as ___ or as small as ___

Answer 21

90 degrees
30 degrees

Question 22

linear probes tend to have relatively _____ footprints with approximately ____elements arranged in a row

Answer 22

large
64-200

Question 23

The FOV of a linear probe is _______ shape but can be ______ if scanning in a ____ mode

Answer 23

rectangular
trapezoidal
vector

Question 24

what is scan line divergence

Answer 24

space between the lines

Question 25

is there scan line divergence in linear array probes

Answer 25

no

Question 26

firing a small single element will ______ divergence = ____ beam = ____ resolution and sensitivity

Answer 26

increase broad poor

Question 27

firing a single element takes away our ability to electronically ____ or ____ the beam

Answer 27

focus steer

Question 28

the larger the point source of sound, the ____ the divergence and the resolution and sensitivity would _____

Answer 28

smaller improve

Question 29

firing in ____ enables electronic transmit focusing and steering while decreasing the divergence

Answer 29

segments

Question 30

what is segmental sequencing and what does it help with

Answer 30

a group of crystals is fired to create a beam followed by a second group that is one crystal down in the row and it helps so that we don't sacrifice information in a linear/curved linear first group is crystal 1,2,3 second is crystal 2,3,4 third is 3,4,5 etc

Question 31

two advantages to curved linear probes

Answer 31

large footprint and FOV (possible to see well in near and far field)

Question 32

disadvantage to curved linear probes

Answer 32

resolution in the far field can be degraded as the distance between the beams is increased

Question 33

what is the process called that corrects grating lobes

Answer 33

apodization

Question 34

what is apodization and what does it help

Answer 34

voltages to the crystals are gradually weakened from the inside out helps prevent grading lobes

Question 35

2 ways to obtain 3D/4D images

Answer 35

freehand using traditional array probe Volumetric probe

Question 36

what is a volumetric probe (how does it create image)

Answer 36

beam is swept over are of interest (electronically or mechanically) to obtain info for 3D reconstruction

Question 37

pixels = voxel=

Answer 37

picture element volume of pixels

Question 38

3 spatial res types

Answer 38

axial: up/down lateral: R/L elevational: front/back (thickness)

Question 39

how is 4D different to 3D

Answer 39

it is 3D but at real time

Question 40

1.5 probes are different to 1 how

Answer 40

they have 1 interface plus Z axis focus at 2 levels (on either side of of crystals)

Question 41

how big are the Z axis focus levels on a 1.5 probe

Answer 41

1/2 thickness of og crystal

Question 42

intravascular probes

Answer 42

scan from within a vessel/lumen

Question 43

transesophageal echo probes

Answer 43

improve visualization of heart by swallowing probe and imaging from within the esophagus

Question 44

dedicated CW probes contain 2 crystals where one ___ and the other ____

Answer 44

transmits receives

Question 45

dedicated CW probes are ____ backed and have a continuos _______ voltage

Answer 45

air AC driving

Question 46

in vascular a CW probe is called

Answer 46

pencil probe

Question 47

in echo a CW probe is called

Answer 47

ped-off probe

Question 48

what are the four different ways to refer to the transducer Q factor

Answer 48

1. resonant f/bandwidth 2. mechanical coefficient 3. energy stored/energy lost 4. reciprocal of fractional bandwidth