Sonography Exam Review Physics Principles

Front 1

ABSORPTION

Back 1

Process whereby sound energy is dissipated in a medium, primarily in the form of heat.

Front 2

ACOUSTIC

Back 2

Having to do with sound.

Front 3

ACOUSTIC IMPEDANCE

Back 3

Resistance of sound as it propagates through a medium.

Front 4

ACOUSTIC VARIABLES

Back 4

Effects on the sound beam caused by the medium. Includes pressure, density, and particle motion (distance, temperature).

Front 5

AMPLITUDE

Back 5

Relating to the strength of the compression wave; maximum variation of an acoustic variable Proportional to power.

Decreases as the wave propagates through tissue.

Front 6

ATTENUATION

Back 6

Weakening of sound as it propagates through a medium.

Proportional to the frequency & penetration depth.

=Attenuation Coefficient (dB)*Path Length (cm)

Air=12.0dB/cm/MHz; Fat=0.6dB/cm/MHz; Bone=10..0dB/cm/MHz

Front 7

ATTENUATION COEFFICIENT

Back 7

Attenuation occurring with each centimeter that sound travels.

Proportional to the frequency & penetration depth. =1/2 frequency(MHz)

Front 8

BANDWIDTH

Back 8

Range of frequencies found in pulse ultrasound.

Inversely proportional to SPL & Q Factor

Front 9

COMPRESSION

Back 9

Region of high pressure or density in a compression wave.

Front 10

CONTINUOUS WAVE

Back 10

A nonplused wave in which cycles repeat indefinitely.

Front 11

CYCLE

Back 11

One complete variation in pressure or other acoustic variable.

Front 12

DECIBEL

Back 12

A unit used to compare the ratio of intensities or amplitudes of two sound waves or two points along the wave.

Front 13

DENSITY

Back 13

Concentration of mass, weight, or matter per unit volume.

Proportional to impedance & propagation speed

Front 14

DISPERSION

Back 14

Dependence of velocity or other physical parameters on frequency.

Front 15

DUTY FACTOR

Back 15

Fraction of time that pulse ultrasound is on.

Proportional to PRF & PD

Inversely proportional to PRP

=PD/PRP

Front 16

FRACTIONAL BANDWIDTH

Back 16

Compression of range of frequencies (bandwidth) with operating frequencies.

=Bandwidth(MHz)/Operating Frequency(MHz)

Front 17

FREQUENCY

Back 17

Number of cycles in a wave occurring in 1 second.

Proportional to image quality & attenuation

Inversely proportional to wavelength, period, & penetration depth

=1/Period

Front 18

FUNDAMENTAL FREQUENCY

Back 18

Original operating frequency

Front 19

HALVE VALUE LAYER (HVL)

Back 19

Thickness of the tissue required to reduce the intensity of the sound beam by one-half.

=3/Attenuation Coefficient(dB/cm)

OR

=6/Frequency(MHz)

Front 20

HARMONIC FREQUENCY

Back 20

Echoes of twice the frequency transmitted into the body that reflect back to the transducer, which improves image quality.

Front 21

HERTZ (Hz)

Back 21

One cycle per second

Unit of frequency

Front 22

IMPEDANCE

Back 22

Determines how much of an incident sound wave is reflected back from the first medium and how much is transmitted into the second medium.

=Medium density(kg/m3)*Medium propagation speed (m/s)

Front 23

INCIDENT ANGLE

Back 23

Direction of incident beam with respect to the medium boundary

= to the reflection angle

Front 24

INCIDENT BEAM

Back 24

Initial or starting beam from transducer

=Reflected beam + Transmitted beam

Front 25

INTENSITY

Back 25

Rate at which energy transmits over a specific area.

Proportional to Power, Amplitude of the wave squared.

Inversely proportional to the beam area

=Power/Area

Front 26

KILOHERTZ (kHz)

Back 26

One thousand cycles per second

Front 27

LONGITUDINAL WAVE

Back 27

Wave traveling in a straight line.

Front 28

OBLIQUE INCIDENCE

Back 28

Incident ultrasound traveling at an oblique able to the media boundary.

Front 29

PERIOD

Back 29

Time to complete one cycle.

Proportional to wavelength

Inversely proportional to frequency

=1/Frequency

Front 30

PERPENDICULAR INCIDENCE

Back 30

Incident ultrasound traveling at an angle perpendicular to the media boundary.

Front 31

PRESSURE

Back 31

Concentration of force.

Proportional to amount of force and volume of the sound beam.

Inversely proportional to the area covered.

Front 32

PROPAGATION SPEED

Back 32

Speed at which a wave moves through a medium.

Proportional to stiffness of medium

Inversely proportional to density of medium.

Air=330m/s;Soft tissue=1540m/s;Bone=4080m/s

Front 33

PULSE

Back 33

A collection of a number of cycles that travel together.

Front 34

PULSE DURATION

Back 34

Portion of time from the beginning to the end of a pulse. Sonography generally uses 2-3 cycles whereas Doppler uses 5-30 cycles per pulse.

Proportional to DF & # of cycles in a pulse.

Inversely proportional to PRF

Front 35

PULSE REPETITION FREQUENCY (PRF)

Back 35

Number of pulses per second.

Proportional to DF

Inversely proportional to imaging depth & PRP

Front 36

PULSE REPETITION PERIOD (PRP)

Back 36

Time between the beginning of one cycle and the beginning of the next cycle.

Proportional to imaging depth

Inversely proportional to PRF

Front 37

PULSE ULTRASOUND

Back 37

A few pulses of ultrasound followed by a longer pause of no ultrasound. During this "Silence", returning echoes are received and processed.

Front 38

QUALITY FACTOR (Q-FACTOR)

Back 38

For short pulsed, the Q-Factor is equal to the # of cycles in a pulse.

The lower the Q-Factor, the better the image quality.

Front 39

RAREFACTION

Back 39

Regions of low pressure or density in a compression wave.

Front 40

RAYLEIGH'S SCATTER

Back 40

Occurs when the reflector is much smaller than the wavelength of the sound beam.

Proportional to frequency.

Front 41

REFLECTED BEAM

Back 41

The beam redirected back to the transducer after striking a media boundary.

Front 42

REFLECTION

Back 42

Redirection (return) of a portion of the sound beam back to the transducer.

IRC=[Z2-Z1/Z2+Z1]2=Reflected/Incident

Fat to muscle = 1%

Fat to bone = 50%

Tissue to air = 100%

Front 43

REFLECTION ANGLE

Back 43

Angle between the reflected sound and a line perpendicular to the media boundary.

Front 44

REFRACTION

Back 44

Change in direction of the sound wave after passing from one medium to another.

Obeys Snell's Law, used to determine amount of rarefaction at an interface.

Front 45

SCATTERING

Back 45

Redirection of sound in several directions on encountering a rough surface.

Proportional to frequency.

Front 46

SOUND

Back 46

A traveling variation of acoustic variables.

Infrasound = less than 20Hz

Audible = more than 20Hz & less than 20,000Hz

Ultrasound = more than 20,000Hz (20kHz)

Front 47

SPATIAL

Back 47

Relating to space

Front 48

SPATIAL PULSE LENGTH (SPL)

Back 48

Distance over which a pulse occurs.

Proportional to wavelength & # of cycles in a pulse.

Inversely proportional to frequency

= # of cycles in a pulse * wavelength

Front 49

SPECKLE

Back 49

Multiple echoes received at the same time generating interference in the sound wave, resulting in a grainy appearance of the sonogram.

Front 50

SPECULAR REFLECTIONS

Back 50

These comprise the boundary of organs and reflect sound in only on direction.

Angle dependent

Front 51

STIFFNESS

Back 51

Resistance of a material to compression.

Front 52

TEMPORAL

Back 52

Relating to time

Front 53

TRANSMITTED BEAM

Back 53

The sound beam continuing on to the next media boundary.

Front 54

VOLUME

Back 54

Amount of occupied space of an object in three dimensions.

Front 55

WAVELENGTH

Back 55

Distance(length) of one complete cycle

Proportional to the period & penetration depth

Inversely proportional to frequency

=Propagation speed/Frequency