CMI 350 CH 1-6 ALL definitions to know

What does unrelated mean?

two items that are not associated

what does related/proportional mean?

when one item increases, the other increases

What does inversely proportional mean?

when one item increases, the other decreases

What is a reciprocal relationship

an inverse relationship where the numbers that are multiplied together equal 1.

what are acoustic variables?

they distinguish sound waves vs. other waves
- sound waves = acoustic waves

what is pressure and its units?

concentration of force in an area
- pascals (Pa)

what is density and its units?

concentration of mass in a volume
- kg/cm^3

what is distance and its units?

measure of a particle in motion
- cm, mm, um

What are transverse waves?

- particles move in a direction is PERPENDICULAR to the direction that the wave moves (propagates)

What are longitudinal wave?

particles that move in the SAME DIRECTION that the wave propagates

What is in phase?

- when peaks of ALL waves occur at the SAME time and at the SAME location
- Nphase waves are NSYNC!!

what is out of phase?

- when the peaks occur at DIFFERENT times and DIFFERENT locations

What is interference?

when MULTIPLE sound beans travel through a medium and arrive at the SAME point at thee SAME exact time

what is constructive interference?

when SEVERAL IN-PHASE waves come together to form a single wave of GREATER amplitude than any of the original in-phase waves

what is destructive interference?

when a PAIR of out-of-phase waves come together and CANCEL out each others amplitude

What is a period?

The TIME required for ONE wavelength to pass a certain point.

What is frequency?

number of cycles that occurs in ONE second

What is infrasound?

frequency BELOW 20 Hz

- below the threshold of human hearing

What is amplitude and its units

Height of a wave
- difference between the maximum value and the average value of an acoustic variable

- decibles (dB), pascals, g/cm^3, cm, mm, um

What is power, its units, and typical values?

rate of energy transfer
- watts
- .004 to 0.09 watts

What is intensity?

concentration of energy in a sound beam
- how the power in a wave spreads or is distributed in space

what is propagation speed? measured by? range and units?

the rate at which a sound wave travels through a medium

- distance divided by time (m/S)
- 500 m/s - 4000 m/s

What is stiffness

- the ability of an object to RESIST compression

what is density in terms of the medium

- relative weight of a material

what is the pulse duration

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

what is spatial pulse length?

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

what is pulse repetition period?

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

What is image depth

(depth of view) the MAX distance into the body an ultrasound machine is imaging

What is pulse repetition frequency (PRF)

the number of pulses that an ultrasound system transmits into the body each second

what is duty factor?

the percentage or fraction of time that a system transmits a pulse

What does spatial mean?

refers to distance or space

what is peak?

maximum value (where the intensity is at its peak)

What is average?

mathematical middle value

What is temporal?

refers to all time!
- transmit (pulse duration) time and receive time

what does pulsed mean?

refers to the transmit time ONLY (pulse duration)

what is Spatial peak intensity (Isp)

Isp: the beams intensity at the location where it is maximum

what is Spatial average intensity (Isa)

Isa: average intensity across the beams entire cross-sectional area

what is temporal peak intensity (Itp)

measured at the instant in time of its maximal value

What is Imax or Im?

Determining the average intensity during the most intense half-cycle

what is pulse average intensity (Ipa)

taking the average intensity during the pulse duration (transmit time)

what is the temporal average intensity (Ita)

averaging the intensity during the entire pulse repetition frequency (both transmit and receiving times)

Isptp is what?

measured at spatial peak and temporal peak (highest)

Isatp is what

measured at spatial average and temporal peak

Ispta is what

measured at spatial peak and temporal average

Isata is what

measured at spatial average and temporal averageIsppa is what

Isppa is what

measured at spatial peak and pulse average

Isapa is what?

measured at spatial average and peak average (lowest)

what is the beam uniformity coefficient?

describes the spread of a beam in space
- unitless with a value of 1 or greater

what is attenuation?

the weakening of sound waves as they travel

what are decibles?

unit for measuring the strength of sound beams as they attenuate

What is reflection?

the portion of the wave energy that is redirected back to the transducer

what is specular

sound is reflected in only one direction and in an organized manner

what is diffuse

reflection radiates in more than one direction

what is scattering

random redirection of sound in many directions

What is Rayleigh scattering?

redirects sound equally in all directions

What is absorption?

when ultrasound energy is converted into another energy form (i.e heat)

Attenuation coefficient

used to REPORT attenuation
- number of decibels of attenuation that occurs when sound travels 1 CM

what is the half value layer thickness?

the distance that sound travels in a tissue that reduces the intensity of sound to 1/2 its original value

what is a thin half-value

high frequency sound

what is thick half-value

low frequency sound

what is impedance?

the acoustic resistance to sound traveling in a medium

What is incidence?

the angle in which a wave strikes the boundary

what is a normal incidence?

sound beam strikes the boundary at exactly 90 degrees

sound beam strikes the boundary at exactly 90 degrees

occurs when incident sound beam strikes the boundary at any other angle other than 90 degrees

What is incident intensity

the sound waves intensity BEFORE it strikes a boundary

What is reflected intensity?

the portion of the incident sound beam that, AFTER striking a boundary, returns back to the transducer

what is transmitted intensity?

is the intensity of the portion of the incident beam, AFTER striking a boundary, continues FORWARD.

intensity reflection coefficient (IRC)

the percentage of the intensity that bounces back when a sound beam strikes the boundary between two media

What is the intensity transmission coefficient (ITC)?

- % of intensity that passes forward

what is refraction

change is direction of wave propagation when traveling from one medium to another