physics exam 3

x, y, and z axis of a mode

x is depth, y is amplitude, no z

a mode is accurate in determining what

depth reflectors or transducer to reflector distance measurements

x, y, and z axis of b mode

x is depth, no y, z is amplitude

what was the first form of grayscale imaging

b mode

x, y, and z axis of m mode

x is time, y is depth, no z

m mode is aka (2)

tm (time-motion) mode, pm (position-motion) mode

transducer types (7)

-mechanical

-electronic transducers

-linear arrays

-convex linear array

-phased array

-vector array

-annular array

mechanical transducers use a _ crystal

single disc shaped

mechanical transducers can only look _

straight ahead

what do mechanical transducers use to generate the scan

moving parts

steering is performed _ in mechanical transducers

mechanically

can the focus of mechanical transducers be changed

no, they are fixed

shape of mechanical transducers images

fan or sector shaped

how will a crystal defect of mechanical transducers affect the image

destroys the whole image

an array consists of

a group of closely spaced piezoelectric elements each with its own electrical connection to the US instrument

an array enables elements to be _

excited individually or in groups to produce a beam

todays transducers are arrays and are _ element

multi

mechanical annular array transducers have _ concentric rings piezoelectric elements

5-10

elements of mechanical annular array transducers are excited sequentially from _, resulting in circular symmetry of beam

inside to out

is electronic steering possible with mechanical annular array transducers

no

primary advantage of annular arrays

multiple transmit focal zones

mechanical annular array transducers use inner crystals for _ and outer crystals for _ regions

shallow, deep

if there is a crystal defect in mechanical annular array transducers, how will it affect image

horizontal band of drop out

disadvantages of mechanical transducers (6)

-parts wear out

-parts break

-motion artifacts

-limited temporal resolution

-excessive grating lobes

-more expensive electronics necessary

linear switched array is a group of elements that can be _

turned on or off (through electronic switches)

most linear switched arrays have over _ elements

200

could linear switched arrays be steered

no

early vascular imaging was produced by

linear switched arrays

linear switched arrays have wide _ images

rectangular

can you change the focus on early sequential array (linear switched array)

no, its fixed

early sequential arrays with crystal defects will have what effect on image

drop out from superficial to deep

linear sequential array has _ rectangular shape strips of piezoelectric material

120-250

how are linear sequential array piezoelectric materials arranged

side by side in a line

sequencing refers to

exciting groups of elements in a specific pattern to linearly scan a region

sequencing is commonly used w/

large linear and curved linear arrays

do sequenced linear arrays have steering

no

how are modern linear sequential arrays focussed

electronically

modern sequential arrays perform both _ focusing using _

transmit and receive, electronic phase delays

focusing of a modern sequential array is achieved with a _ excitation pattern of the elements, and are outer or inner crystals fired earlier

curved, outer

color doppler in a modern sequential array is parallelogram shaped bc _

electrical spike patterns creating the doppler sound beam are sloped

can focusing occur during reception

yes

more accurate images can be created when receiver introduces _ to some of the electrical signals during _

time delays, reception

optimal time delays depend on what

depth

a channel is the combination of (3)

active element, wire, system electronics

is receive focusing controlled by operator

no

how is receive focusing done

dynamically

dynamic receive focusing is applied at what depths

all

does dynamic receive focusing slow down frame rate

no

dynamic receive focusing is aka (3)

-aperature focusing

-dynamic aperature

-beam aperature focusing

are more or fewer elements used for shallow echoes

fewer

changing the active number of pzt crystals keeps the beam _ to optimize _ resolution

narrow, lateral

todays transducers are called _ and contain _ elements

arrays, multiple

types of array transducers (4)

-linear phased array

-convex array

-phased array

-vector array

two advantage software arrays

enable electronic beam steering and electronic focusing

phase difference is

amount of time shift necessary to make two waves align

steering for each beam is achieved by introducing _

nano-second time delays

_ between excitation pulses drive the elements of a phased array transducer

phase delays

2d image is _ with electronic steering or phasing

built up

transmit electronic steering pulses are directed in a pattern similar to a

windshield wiper sweeping

phased delays are also used to _

focus transmit and receive beams

arrays allow selection of the _ by the sonographer

transmit focus distance

whenever you see a straight line in an image of wavelets, its an _ beam

unfocused

activating multiple focus zones increases the number of _ required to make an image

pulses

having multiple focal zones _ the frame rate

lowers

disadvantage of multiple focus zones

diminishes temporal resolution

advantage of multiple focal zones

better lateral resolution

the beam former is the component of the us system that creates _ during

electronic patterns (delays), transmission and reception

beam former corrdinates the _ sent to each active element (during transmission)

electrical signals

beam former also adjusts electrical spike voltages to reduce _

lobe artifacts (apodization)

beam former coordinates _ sent to each active element thereby optimizing the

electrical signals, transmitted ultrasound beam

during reception the beam former establishes the correct _ used for _

time delays, dynamic receive focusing

advantages of beam former (3)

stability, programmability, acceptance of wide range of frequencies (broadband)

beam former has a _ switch that is important during both transmission and reception

transmit-receive

switch in beam former protects the delicate _ components from the powerful signals created for pulse transmission

receiver

phase arrays have how many elements of what shape

64-128, rectangular or square

how are elements in phased arrays packed

tightly in a small area (not side by side)

frequency range for phased array probes

2-8 MHz (up to 12 MHz for pediatric cardiac patients)

phased arrays have a _ footprint that is _ shaped

small, sector or pie

unlike linear and convex array transducers, phased array transducers has how many elements in the scan head producing and receiving echoes

all

convex array has how many elements and what shape

120-250, rectangular shaped

how are crystals arranged in convex/curvilinear arrays

side by side in a bowed line

are convex/curvilinear array beam lines parallel

no, they emerge at different angles like spokes of a wheel

frequency range of convex/curvilinear arrays

2-10 MHz

how many crystals are fired simultaneously in convex/curvilinear array

some but not all

shape of convex/curvilinear array images

blunted or sector shape

focusing of convex/curvilinear arrays are _ and steering is in _

electronic, many directions/electronic

what are convex or curvilinear array probes used for

abdominal scans

malfunction of convex array crystal will have what effect on image

top to down dropout

malfunction of phased array crystal will have what effect on image

top to down dropout

linear transducers are used for

vascular

frequency range for linear phased array

5-18 MHz

linear phased arrays replaced which probes

switched arrays

linear phased arrays produce what image shape

rectangular

linear phased arrays have how many elements of what shape

200-300, rectangular

how are linear phased arrays steered and focussed

electronically

linear array hockey stick frequency range and footprint size

5-9 MHz, 25mm

what is linear array hockey stick used for

vascular and small parts

vector arrays are a combination of

linear sequential and linear phased array

how are vector arrays steered and focussed

electronically

vector arrays have how many crystals of what shape

120-250 rectangular shaped