Ultrasound System Components

Question 1

Amplification(Receiver)

Answer 1

all signals are treated identically

entire image gets brighter or darker

It is adjustable

(Gain/Overall Gain Knob)

Question 2

Compensation(Receiver)

Answer 2

creates an image of uniform brightness from top to bottom by compensating for the weakening of the soundwave as it travels through the medium

It is adjustable

Question 3

Compression(Receiver)

Answer 3

performed twice

first-keeps the electrical signal level within the accuracy range of the system’s electronics

second-keeps the image’s grayscale content within the range of detection of the human eye (aprox 20 shades of gray)

It is adjustable

Question 4

Demodulation(Receiver)

Answer 4

two part process that changes the electrical signals in the receiver into a form more suitable for the monitor

rectification-converts all negative voltages into positive voltages, corrects for, or eliminates, negative voltages

smoothing(enveloping)-places a smooth line around the “bumps” and evens them out

Question 5

Reject(Receiver)

Answer 5

controls whether low-level signals will be displayed on the image

desirable to display low-level reflections that contain meaningful info

low-level noise should not appear on image

rejection affects all low-level signals on the image, does not affect bright echoes

Question 6

transducer

Answer 6

transforms electrical energy into acoustic energy

during reception, it converts the returning acoustic energy into electrical energy

Question 7

display

Answer 7

presents processed data

the display may be a flat screen monitor, a transparency, a spectral plot, or a variety of other formats

Question 8

display controls

Answer 8

contrast-determines the range of brilliancies within the displayed image

brightness-determines the brilliance of the displayed image

Question 9

scan converters

Answer 9

store info then display it

grayscale imaging made possible

translates the info from the spoke format into the video format

used analog technology

digital scan converters use computer technology

Question 10

limitations of analog scan converters

Answer 10

image fade-stored charges on the silicon wafer dissipate over time

image flicker-caused by switching between read and write modes

instability-picture quality depends on many factors, including length of use, room temp, and humidity

deterioration-image degrades as device ages

Question 11

advantages of digital scan converters

Answer 11

uniformity-consistent grayscale quality throughout the image

stability-does not fade or drift

durability-not affected by age or heavy use

speed-nearly instant processing

accuracy-error free

Question 12

important elements of digital scan converters

Answer 12

pixel-smallest building block of a digital picture

pixel density-number of picture elements per inch

low pixel density-few pixels/inch, larger pixels, less detailed image, lower spatial resolution

high pixel density-many pixels/inch, smaller pixels, more detailed image, higher spatial resolution

bit-smallest amount of computer memory

fewer bits/pixel-fewer shades of gray, degraded contrast resolution

more bits/pixel-more shades of gray, improved contrast resolution

Question 13

preprocessing

Answer 13

manipulation of image data before data storage:

time gain compensation

log compression

write magnification

persistence

spatial compounding

edge enhancement

fill-in interpolation

Question 14

postprocessing

Answer 14

manipulation of image data after storage:

any change after freeze frame

black/white inversion

read magnification

contrast variation

3D rendering

Question 15

Storage

Answer 15

archives the ultrasound studies

typical storage devices(media):

computer hard drives, CD/DVD, videotape, magneto-optical discs, paper printouts, photographs, USB drives

Question 16

Pulser

Answer 16

determines amplitude, pulse repetition period(PRP), and pulse repetition frequency(PRF)

pulser is low-image is dark

pulser is high-image is bright

PRP and PRF are reciprocals

Question 17

master synchronizer

Answer 17

maintains and organizes the proper timing and interaction of the system’s components

Question 18

beam former

Answer 18

determines the firing delay patterns for phased array systems

it receives the pulser’s single electrical spike and distributes it to the numerous active elements of an array transducer

switch-protects the sensitive electrical components in the receiver from the high voltages created during transmission

during pulse creation-voltages from the system to the transducer are very high

during reception-voltages from the transducer back to the system are very low

Question 19

receiver

Answer 19

transforms the electrical signals from the transducer(produced by the reflected sound) into a form suitable for display on the system’s monitor

five operations must be performed in the correct order for the system to function properly:

1)amplification 2)compensation 3)compression 4)demodulation 5)reject