Ch 12 2D Imaging

contain a single, circular disc shaped active element that is physically moved

mechanical transducer

mechanical transducers can only have _____ active element

one

active element in mechanical transducers is shaped like a

coin

mechanical transducers create a _______ shaped image

fan or sector

with mechanical transducers, the crystal is rotated by a

motor

with mechanical transducers, a scan plane is created through ______ steering

mechanical

mechanical transducers have a _____ focal depth

fixed

fixed focal depth is done through _______ and ______ focusing

internal, external

if the crystal malfunctions with mechanical transducers, the ________ is lost

entire image

modern transducers are generally

arrays

arrays contain _______ active elements

multiple

a single slab of PZT cut into a collection of separate pieces called elements

an array

a collection of separate pieces of PZT

elements

each active element is connected by a _____ to its own electronic circuitry in the US system and acoustically isolated from its neighboring crystals

wire

array transducer where active elements are arranged in a straight line

linear array

array transducer where active elements are arranged as circular rings with a common center

annular

array transducer where active elements are arranged in a bowed or arched line

convex

linear array transducers have a ______ footprint

small

linear array transducers have ___ moving parts

no

linear array transducers have ________ elements arranged along the face of the probe

100-300

linear array transducer elements are narrow and _______ shaped, side by side along the face of the transducer

rectangular

linear array transducer elements have a width of ________ of the sounds wavelength

1/4 - 1/2

linear array transducers produce a ______ shaped image

sector

linear array transducers have an electronic steering process called ______ to build the image

phasing

linear array transducers have a _____ focusing capability

multi

linear phased array transducers are focused _______

electronically

damage to a linear array transducer results in

inconsistent beam steering and focusing

_____ of the active elements in a linear array transducer are fired to create each sound pulse

all

the pattern of electrical signals from the US system determines the sound beams _______ and ______

direction , focus

time differences between the excitation of the elements

phase delays

the electronics within the US system that create beam steering patterns are called

the beam former

to focus the sound beam, the beam former excites the crystals in a ______ pattern

curved

the _____ crystals are excited earlier than the _____

outer , inner

a sound beam can only have _____ focus

one

to create an image with multiple foci at different depths, the US system must send multiple _____ down each scan line

sound beams

if there is an image with 3 focal points, how many pulses are transmitted down each scan line?

3 distinct sound pulses

focusing may also occur during

reception

annular phased array transducers have ________ ring-shaped elements with a common center

multiple

with annular array, the _____ rings acquire data from shallower depths, while the _____ rings acquire data from deeper regions

inner , outer

annular array transducers steer ______

mechanically

annular array transducers can have multiple _______ in each scan line because each crystal has their own

focal zones

annular transducers produce a ______ shaped image

fan or sector

when one ring of an annular array transducer malfunctions, only a ______ of the image is lost

portion

malfunction of an array transducer appears as a ______ band of dropout at a particular depth

horizontal

linear sequential array transducers have a ______ acoustic footprint

large

linear sequential array transducers have _______ of PZT arranged side by side

120-250

with linear sequential array transducers, each crystal is about ___ wavelength thick

1

with linear sequential array transducers, the sound beams are parallel to each other and directed ______

straight ahead

linear sequential array transducers produce a _______ image that is never wider than the transducer

rectangular

with linear sequential array transducers, if one element is damaged in a transducer, only the portion of the image ________ the damaged element is affected

directly below

linear sequential array transducers can be steered electronically using

sloped-patterned phase delays

sloped patterned phase delays create _______ shaped images vs rectangular

parallelogram

- convex

- curved

- curvilinear array

all the same word

convex array transducers have ______ strips of PZT in a bowed line

120 - 250

with convex array transducers, each active element is about ____ wavelength thick

1

with convex array transducers, a group of crystals are fired simultaneously to create a sound beam. Because they are arranged in a bowed arc, the pulses travel in _______ directions as they leave the transducer

different

with convex array transducers, there will be _______ transmit focusing and _______ receive focusing used

electronic , dynamic

convex array transducers produce _____ shaped images

blunted sector

with convex array transducers, if there is damage to a crystal, there will be ______ drop out from the damaged crystal

vertical

transducer with combination of linear sequential and linear phased arrays

vector array

vector array transducers have _____ delay patterns that can electronically steer the sound beams in different directions

sloped phase

vector array transducers have ______ rectangular shaped strips of PZT, arranged side-by-side in a line

120 - 250

beam steering with vector array transducers combines both ______ and ______ array technologies

linear sequential, linear phased

vector arrays produce _______ shaped images

trapezoidal

with vector array transducers, ________ focusing is used in both transmit and receive

electronic

answers the question, are the reflections on the image created from structures directly in the imaging plane or from structures that lie above or beneath the imaging plane

slice thickness resolution

slice thickness resolution, AKA

elevational resolution

slice thickness is measured in a direction ______ to the imaging plane or above-to-below the imaging plane

perpendicular

beam thickness varies with

depth

active elements that are _____ shaped provide the thinnest US slices and the best elevational resolution within the focal zone

disc

with disc shaped elements, the elevational resolution is identical to the _______ resolution

lateral

with phased, linear, and convex array transducers, the beam is focused/narrowed only ______ in the imaging plane, not above and below

side to side

with phased, linear, and convex array transducers, the narrowing improves lateral resolution but not ________

slice thickness

newer transducers that create thinner beams with improved slice thickness resolution over a greater range of depths

one and one half dimensional arrays

the face of the 1 and 1/2 array transducer has numerous crystals arranged side by side, but also multiple arranged ________

up and down

______ slices improve elevational resolution

thin

AKA volume imaging

3D imaging

3D imaging is done by using a 2D array with _______ of elements arranged in a checkerboard pattern

thousands

creates computer generated images

3D imaging

off axis sound beams

side lobes

if the side lobes are of sufficient intensity, structures within them can generate reflections and create

artifacts

reflections in side lobes degrade _______ resolution

lateral

grating lobes are created by ______ transducers

array

extra, off-axis sound beams that degrade lateral resolution

grating lobes

modern transducers use a process called _________ to reduce side and grating lobes

apodization

______ lobes can be eliminated if the strength of the electrical spikes sent to each crystal differs

grating

with linear array transducers, _______ is used to reduce grating lobes

subdicing

a crystal is divided into a group of smaller crystals called sub-elements

subdicing

used to make a sound beam narrow over a greater range of depths

dynamic aperture

dynamic aperture improves _______ resolution

lateral

dynamic aperture, AKA

variable aperture

with an array transducer, the US system can change the number of crystals along the face being used to transmit pulses and receive reflections

dynamic aperture