SPI Review Flashcards
What type of wave is sound?
A mechanical longitudinal wave
Sound requires particles to move and propagates through a medium.
What are the acoustic variables associated with sound?
- Pressure
- Density
- Particle motion
What type of wave is NOT sound?
Transverse wave
In transverse waves, acoustic variables occur perpendicular to the direction of the wave.
What is the frequency range for audible sound?
20 Hz to 20,000 Hz (20 kHz)
What happens to axial and lateral resolution as frequency increases?
They improve but with more attenuation and less penetration.
How is the period of a sound wave calculated?
1/Frequency (MHz)
What does wavelength represent in sound waves?
Distance of one cycle (mm)
What determines the speed of sound in a medium?
Stiffness and density
Stiffness (bulk modulus) predominates in determining speed.
What is GRT in ultrasound physics?
Go and return time, where for every 13 microseconds, sound travels 1 cm.
What is amplitude in ultrasound?
Strength of the wave, measured in any acoustic variable unit.
How is power related to amplitude in ultrasound?
Power is proportional to the square of amplitude (Power ~ Amplitude^2).
What is intensity in ultrasound?
Power per unit area (Intensity ~ Power/Area)
What is the relationship between area and intensity?
If area is halved, intensity is doubled.
What does spatial peak intensity refer to?
Highest intensity in the center of the beam.
What is the duty factor (DF) in pulsed ultrasound?
Percentage of time the pulse is on (PD/PRP).
What is the relationship between pulsed ultrasound and continuous wave ultrasound?
Pulsed ultrasound has range resolution due to timing, while continuous wave does not.
What is attenuation?
Decrease in intensity and amplitude
Units are decibels, always negative.
What are the components of attenuation?
- Absorption
- Reflection
- Scattering
What is absorption in ultrasound?
Conversion of sound energy to heat, affected by viscosity and frequency.
What is the formula for total attenuation ?
AC x Distance
What is acoustic impedance?
Speed of sound x Density
What is the reflection coefficient (IRC) formula?
(Z2 - Z1) / (Z2 + Z1) to the second power
What does the transmission coefficient (ITC) represent?
100 - IRC
What is Rayleigh scattering associated with?
Frequency to the fourth power
It is significant in red blood cells.
What is speckle in ultrasound imaging?
A form of scattering from constructive and destructive interference.
What does refraction refer to in ultrasound?
Bending of the transmitted sound beam due to different propagation speeds and oblique angles.
What is Snell’s law used for in ultrasound?
To determine the transmission angle and speeds of the medium.
What are the terms of echogenicity in ultrasound?
- Echogenic
- Anechoic
- Hyperechoic
- Hypoechoic
- Isoechoic
