SPI CHAPTER 3

What are the units for period?

time (s, ms, µs)

In clinical imaging, frequency ranges from approximately ____ to ____.

2 MHz to 15 MHz

Infrasound frequency

less than 20 Hz

Audible sound frequency

between 20 Hz and 20 kHz

Ultrasound frequency

greater than 20,000 Hz (20 kHz)

What are the 7 acoustic parameters?

Period, frequency, amplitude, power, intensity, wavelength, propagation speed

What do acoustic parameters do?

Describe the features of a sound wave

_ is the time from the start of one cycle to the start of the next cycle.

Period

_ is the number of cycles that occur in one second.

Frequency

What are the units for frequency?

Hertz (Hz)

Period and frequency relationship

Inversely related and reciprocals

What are the 3 “bigness” parameters?

Amplitude, power, intensity

_ is the bigness of a wave.

Amplitude

Amplitude is determined by ____ source.

sound

For amplitude can it be controlled by the sonographer

true

Amplitude ___ as sound propogates through the body.

decreases

Amplitude as sound propagates through the body.

Decreases

What is the difference between amplitude and peak-to-peak amplitude?

Peak-to-peak amplitude is twice the value of the amplitude

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

Power

What is the unit for power?

Watts

Power is determined by the ___ source. Power ___ as sound propagates through the body.

sound , decreases

Power ___ adjustable by the sonographer

is

Power and intensity are both proportional to .

amplitude²

_ is the concentration of energy in a sound beam.

Intensity

Intensity is determined by the ___ source. And ___ adjustable by the sonographer.

sound, is

What is the unit for intensity?

W/cm²

_ is the distance or length of one complete cycle.

Wavelength

Wavelength is the only parameter determined by .

both the source and the medium

Wavelength ___ adjustable by the sonographer

is not

Wavelength and period relationship

Inversely

_ is the rate at which a sound wave travels through a medium.

Propagation speed

Propagation speed is determined by the . And ___ adjustable by the sonogpraher.

Medium, is not

What is the speed of sound in lung?

500 m/s

What is the speed of sound in fat?

1,450 m/s

What is the speed of sound in soft tissue?

1,540 m/s or 1.54 mm/µs or 1.54 km/s

What is the speed of sound in the liver?

1,560 m/s

What is the speed of sound in blood?

1,560 m/s

What is the speed of sound in muscle?

1,600 m/s

What is the speed of sound in tendon?

1,700 m/s

What is the speed of sound in bone?

3,500 m/s

Sound travels fastest in

solids

Sound travels slower in

liquids

Sound travels slowest in

gases

What 2 characteristics of a medium affect the speed of sound?

Stiffness and density

Stiffness and speed are _ related.

directly

What is another name for stiffness?

bulk modulus

_ is the opposite of stiffness.

Elasticity or compressibility

Density and speed are _ related.

inversely

_ has the greatest influence on speed.

Stiffness