physics chapter 12

2-d imaging

what 2 characteristics of sound make 2-d images challenging to make

sound travels in a straight line and it must be narrow to optimize lateral resolution

what overcomes the 2 challenging characteristics of sound to make 2-d images

multiple pulses

what shape active element does a mechanical transducer have

disc-shaped

how many active elements does a mechanical transducer have

1

the image created by a mechanical transducer is

fan or sector shaped

the greater the depth, the _____ the lateral resolution

worse

mechanical transducer uses ______ steering

mechanical

mechanical transducers have a ________ focal depth

fixed

2 methods of focusing for a mechanical transducer

internal and external

the use of a curved active element is ______ focusing

internal

the use of an acoustic lens is _____ focusing

external

T or F: focusing occurs both in the horizontal and vertical plane

true

what is the shape of a mechanical transducer’s sound beam

hour glass

when a mechanical transducer is damaged what happens

the entire image is lost

arrays contain how many active elements

multiple

a collection of separate pieces of PZT

elements

the combination of the active element, wire, and system electronics

channel

3 types of array transducers

linear, annular, convex

T or F: a linear phased array has no moving parts

true

in a linear phased array, the beam is steered using an electrical technique called

phasing

linear phased array transducers have a _____ footprint

small

how many active elements does a linear phased array transducer have

many

the image created by a phased array transducer is

fan or sector shaped

electronic steering is called

phasing

a linear phased array uses _______ steering

electronic

linear phased array transducers are focused

electronically

damage to one of the elements in a phased array transducer results in

inconsistent or erratic beam steering and focusing

sloping is

steering

curving is

focusing

when electrical spikes all hit the same time, the beam goes

straight down

how many active elements in a linear phased array probe are fired to create each sound pulse

all

wavelets in a linear phased array transducer interfere constructively or destructively?

both

this is an example of

steering

this is an example of

focusing

the electronics within the ultrasound system that create beam patterns is called the

beam former

when the spike pattern is a straight line, the beam is

unfocused in a specific direction

in a multi-focus system, the pattern with the greatest curvature creates the beam with the ___________ focus

shallowest

curvature and focal depth are ______ related

inversely

T or F: focusing may also occur during reception

true

does the sonographer have control over dynamic receive focusing

no

the shape of annular phased array active elements are

disc-like

how many active elements does an annular phased array transducer have

multiple

annular phased array uses ________ steering

mechanical

annular phased array transducers have _______ focal zones

multiple

the PZT with the smallest diameter in annular phased array transducers created the ______ focus beam

shallow

annular phased array transducers produce a _________ shaped image

fan or sector

if one of the active elements in an annular phased array transducer is damaged what occurs

horizontal dropout

if the innermost ring of an annular phased array transducer is damaged then the most _________ region of the image will be lost

superficial

this is an example of damage to an

annular phased array transducer

a linear sequential array transducer has a _____ footprint

large

a linear sequential array transducer creates what shape image

rectangular

linear sequential array transducers have ______ active elements

many

how many crystals are fired at once when using a linear sequential array

small groups

linear sequential array transducers are focused

electronically

in linear sequential arrays, ________ _________ _______ is achieved with curved excitation patterns of the active elements

electronic transmit focusing

when a linear sequential array transducer is damaged what occurs

dropout directly below the damaged PZT

this is an example of damage to a

linear sequential array transducer

linear sequential array transducers are steered

electronically

when a linear sequential array transducer is steered it creates a

parallelogram shape

this is an example of a

steered linear sequential array transducer

a convex array transducer has how many active elements

many

a convex sequential array transducer has how many crystals fired simultaneously

some but not all

a convex array transducer is focused

electronically

the shape of a convex array transducer is

blunted sector

when one active element of a convex array transducer is damaged

only the portion directly below the damaged PZT is lost

this is an example of damage to a

convex array transducer

a combination of a linear sequential and linear phased array is called a

vector array

a vector array transducer has _____ active elements

multiple

how many crystals are fired to steer a vector array transducer

some but not all

a vector array transducer is focused

electronically

a vector array transducer creates a _________ shaped image

trapezoid

this image was produced by a

vector array transducer

________ is accuracy in imaging

resolution

slice thickness is described as ______ _ ______ the imaging plane

above to below

T or F: thickness can vary with depth

true

what shape active element produces the best elevational resolution

disc-shaped

what transducers produce the best elevational resolution

mechanical and annular phased array transducers

what is used to create thinner slices in phased array, linear array, and convex array transducers

acoustic lens

phased array, linear array, and convex array transducers have the best _______ resolution

axial

a 1 and ½ dimensional array transducer has multiple crystals in the _____ ___ ______ direction

up and down

creates an image from 3-d data

rendering

real time 3D

4D

single element transducers create a sound beam with what shape

hourglass

side lobes degrade

lateral resolution

what are side lobes called when created by array transducers

grating lobes

grating lobes ______ lateral resolution, _____ image quality, and create ______

degrade, reduce, artifacts

reducing the strength of side and grating lobes is achieved by a process called

apodization

a crystal is divided into a group of smaller crystals

subdicing

subdicing also reduces

grating lobes

the process of changing the aperature is called

dynamic aperature

making a sound beam more narrow over a greater range of depths and optimizing lateral resolution

dynamic aperature

dynamic aperature improves

lateral resolution