Ultrasound Basic Physics Principles

Question 1

Wavelength

Answer 1

Distance over which a wave repeats itself during one period of oscillation

Question 2

Power

Answer 2

Rate of energy flow over the entire beam of sound

Question 3

Intensity

Answer 3

Power per unit area

Question 4

Attenuation

Answer 4

Reduction in amplitude and intensity of a sound wave as it propagates through a medium

Question 5

Frequency

Answer 5

Number of cycles per second that a periodic event or function undergoes

Question 6

Refraction

Answer 6

Change in the direction of propagation of a sound wave transmitted across an interface where the speed of sound varies

Question 7

Amplitude

Answer 7

Strength of the ultrasound measured in decibels

Question 8

Decibel (dB)

Answer 8

Unit used to quantitatively express the ratio of two amplitudes or intensities

Question 9

Pulsed Repetition Frequency

Answer 9

In pulse-echo instruments, it is the number of pulses launched per second by the transducer

Question 10

Acoustic Propagation Properties

Answer 10

The effects of soft tissue on ultrasound

Question 11

Biological Effects

Answer 11

Effects of the sound wave upon the biologic tissue

Question 12

Pressure

Answer 12

Concentration of force within an area, force/area

Question 13

Density

Answer 13

Concentration of mass within a volume

Question 14

Distance

Answer 14

Measure of Particle motion

Question 15

Transverse Wave

Answer 15

Particles move in a perpendicular direction (Right angles or 90 degrees) to the direction of the wave

Question 16

Longitudinal Wave

Answer 16

Particles move in the same direction as the wave

Question 17

Period

Answer 17

Time required to complete a single cycle; time from start of cycle to start of next cycle

Question 18

Propagation Speed

Answer 18

Rate that sound travels through a medium, also called velocity or speed

Question 19

In-phase Wave

Answer 19

Amplitude of new, combined wave is greater than original two waves

Question 20

Out-phase Wave

Answer 20

Amplitude of new, combined wave is less than one of the original wave

Question 21

Pulse Duration

Answer 21

The actual time from the start of a pulse to the end of that pulse

Question 22

Spatial Pulse Length

Answer 22

The distance that a pulse occupies in space from the start to the end of a pulse

Question 23

Pulse Repetition Period

Answer 23

The time from the start of one pulse to the start of the next pulse

Question 24

Duty Factor

Answer 24

The percentage or fraction of time that the system is transmitting a pulse

Question 25

Rayleigh Scattering

Answer 25

Light scatters in every direction due to smaller particles

Question 26

Attenuation Coefficient

Answer 26

Is the number of decibels of attenuation that occurs when sound travels one centimeter or the amount of attenuation per CM

Question 27

Absorption

Answer 27

Is the most sizable component of attenuation

Question 28

Half Value Layer Thickness

Answer 28

Is the distance that sound travels in a tissue that reduces the intensity of sound to half its original value

Question 29

Pulsed Sound

Answer 29

A collection of cycles that travel together

Question 30

Impedance

Answer 30

The total opposition to the flow of sound energy

Question 31

Scattering

Answer 31

Deflection of sound when it strikes a reflecting surface

Question 32

Specular Reflection

Answer 32

Reflection from a very smooth surface

Question 33

Diffuse Reflection

Answer 33

Reflection from a relatively rough surface

Question 34

Constructive Interference

Answer 34

Displacements of the two waves are in the same direction. The two waves are said to be "in phase" (The phase difference is 0 degrees)

Question 35

Destructive Interference

Answer 35

Displacements of the two waves are in the opposite direction. The two waves are said to be "out of phase" (The phase difference is 180 degrees)

Question 36

Stiffness

Answer 36

The resistance of material to compression

Question 37

Density

Answer 37

The concentration of matter (Mass per unit volume)

Question 38

Peak

Answer 38

The highest intensity area or time of the sound beam (Maximum value)

Question 39

Average

Answer 39

Take peak, low, and medium intensities and average them together to get average intensity (Mean value)

Question 40

Temporal

Answer 40

Occurs with time

Question 41

Spatial

Answer 41

Related to space/area of the beam

Question 42

Snell's Law

Answer 42

A law in physics: the ratio of the sines of the angles of incidence and refraction is constant for all incidences in any given pair of media for electromagnetic waves of a definite frequency

Question 43

Range Equation

Answer 43

A relationship between the distance to a reflector and the time it takes for a pulse of ultrasound to propagate to the reflector and return to the transducer

Question 44

Normal Incidence

Answer 44

90 degrees

Question 45

Oblique Incidence

Answer 45

Anything other than 90 degrees (Not right angles)

Question 46

Directly Proportional

Answer 46

Increasing or decreasing together with a constant ratio

Question 47

Related or Proportional

Answer 47

Properly related in size, degree, or other measurable characteristics; corresponding

Question 48

Inversely Proportional

Answer 48

Related so that as one becomes larger the other becomes smaller

Question 49

Reciprocal Relationship

Answer 49

A relation of mutual dependence or action or influence

Question 50

13 Microsecond Rule

Answer 50

In soft tissue, every 13 micro sec of go-return time means the reflector is 1 cm deeper in the body

Question 51

Medium

Answer 51

Tissue through which sound travels

Question 52

Source

Answer 52

The transducer and ultrasound machine

Question 53

Pulsed Wave

Answer 53

Any modality which turns the transmitter on and off periodically so as to reduce range ambiguity