Key Terms Week1/Lecture1

Question 1

Analog Scan Converter

Answer 1

first type of scan converter

made grayscale imaging possible

no longer used in modern equipment

Question 2

B-Mode

Answer 2

brightness mode

A-mode signal converted to dots that vary in brightness depending on the strength of the returning echo

stronger echo=brighter dot

Question 3

Cavitation

Answer 3

the formation of gas-or vapor-filled cavities

Question 4

Digital Scan Converter

Answer 4

uses computer memory to digitize the image and transfer it to the display monitor

Question 5

Doppler Effect

Answer 5

when a source of wave motion moves, the apparent frequency of the emitted wave changes

Question 6

Grayscale Imaging

Answer 6

varying shades of gray that are produced from an analog scan converter

Question 7

M-Mode

Answer 7

series of B-Mode dots that are displayed on a moving time base to graph moving structures

formed the basis of echocardiography before real-time scanning

today it is used in conjunction with real-time imaging

Question 8

Piezoelectric Effect

Answer 8

a mechanical deformation results when an electrical field(voltage) is applied to the crystal, the crystal resonates mechanically

when the crystal resonates mechanically, it produces a voltage

material most commonly used is lead zirconate titanate

Question 9

Real-Time Imaging

Answer 9

recording moving structures

real-time B-mode ultrasound systems use a transducer, which contains a crystal that can convert ultrasound impulses into electrical impulses

signals are integrated by a computer(scan converter)

Question 10

Therapeutic Ultrasound

Answer 10

between .5MHz and 3MHz

beam intensities results in tissue temperature rises as high as 4 degrees Celcius and up to depths of about 5cm

used to increase blood flow and manage several soft tissue conditions

Question 11

3D Imaging

Answer 11

like a 2D image, except instead of sound waves being sent vertically, they are sent from many angles, and the returning echoes can be used to build and display a volume image in 3D

Question 12

4D Imaging

Answer 12

3D image with real-time imaging

Question 13

Diagnostic Ultrasound

Answer 13

2MHz-12MHz

frequencies below 2MHz has poor resolution

frequencies above 12MHz does not penetrate deep into the patient

Question 14

Transverse Waves

Answer 14

particles move in a direction that is perpendicular (at right angles) to the direction that the wave propagates (moves)

Question 15

Longitudinal Waves

Answer 15

particles move in the same direction that the wave propagates (moves)

Question 16

Compression

Answer 16

squeezed together

Question 17

Rarefaction

Answer 17

stretched apart

Question 18

Medium

Answer 18

tissue

some type of material

Question 19

Acoustic variables-pressure

Answer 19

concentration of force in an area

units: pascals(Pa), kg/m2

compression phase-pressure increases

rarefaction phase-pressure decreases

Question 20

Acoustic variables-density

Answer 20

concentration of mass in a volume

units: kg/cm3

compression phase-density increases

rarefaction phase-density decreases

this leads to nonlinear imaging technique-harmonic imaging

Question 21

Acoustic variables-distance

Answer 21

measure of particle motion

units: cm, feet, mile, etc.

Question 22

Acoustic parameters-period

Answer 22

the time it takes a wave to vibrate a single cycle

the time from the start of one cycle to the start of the next cycle

units: microseconds, seconds, hours, days

not adjustable

Question 23

Acoustic parameters-frequency

Answer 23

number of cycles that occurs in one second

units: hertz(Hz)

Hertz equals per second

not adjustable

Question 24

Acoustic parameters-amplitude

Answer 24

the “bigness” of a wave

the difference between the maximum value and the average or undisturbed value of an acoustic variable

the difference between the minimum value and the average value of the acoustic variable

units: units of any of the acoustic variables

Question 25

Acoustic parameters-power

Answer 25

the “bigness” of a wave

rate of energy transfer or the rate at which work is performed

units: watts

It is adjustable

Question 26

Acoustic parameters-intensity

Answer 26

the “bigness” of a wave

the concentration of energy in a sound beam

units: watts(W), W/cm2

It is adjustable

Question 27

Acoustic parameters-wavelength

Answer 27

the distance or length of one complete cycle

units: mm, meters, other units of length

not adjustable

Question 28

Acoustic parameters-propagation speed

Answer 28

the rate at which a sound wave travels through a medium

units: m/sec, or any other distance/time

not adjustable

Question 29

Hertz

Answer 29

events per second

units that frequency is measured by

Question 30

Infrasound

Answer 30

sound waves with frequencies lower than 20Hz

Question 31

Audible sound

Answer 31

between 20Hz and 20,000Hz

Hertz(Hz): standard unit of frequency equal to 1 cycle per second

Question 32

Ultrasound

Answer 32

between 1 and 30MHz (1,000,000-30,000,000Hz)

do not exist in a vacuum

movement in gases is poor because the molecules are widely separated

the closer the molecules are, the faster the sound wave moves through the object

Question 33

A-Mode

Answer 33

Amplitude Mode

the distance between the transducer and the structure determines where an echo is seen along the time axis

(Obsolete)