Equations + general
5 MHz equals how many Hz?
5,000,000 Hz
What is the difference between wavelength and period?
Wavelength is the length of space one cycle takes up.
Period is the time it takes for one cycle to occur
1. What is the SPL of a three-cycle pulse with a wavelength of 0.77mm?
2. What is SPL expressed in what unit
1.2.31 mm
0.77mm x 3=2.31mm
SPL (mm) = wavelength (mm) × Number of cycles in the pulse
2. Millimeter (mm)
Define the following terms in relation to a soundwave
compression:
rarefactions:
compression: areas of high pressure and density
rarefactions: areas of low pressure and density
Define Duty Factor + it's unit:
Fraction of time that pulsed ultrasound is on.
Unitless but it is a %
What is the equation for Pulse Repetition Period (PRP)
PRP (ms) = 1 / PRF (kHz) or
1 / PRF (kHz) = PRP (ms)
The change of this shape, introduces harmonics
sinusoidal
Since period and frequency have an inverse relationship, what is the period for a probe producing 8 MHz?
0.125 microseconds (µs)
1/8MHz = 0.125 microseconds
What are the three acoustic variables needed to produce a soundwave?
Pressure
density
Particle motion
1. Define Impedance:
2. Would the impedance be greater from tissue to tissue, or tissue to air?
1. determines how much of an incident sound wave is reflected back and how much is transmitted into the second medium
2. Tissue to air
1. How do contrast agents enhance echogenicity?
2. What causes scattering of an ultrasound beam?
1. The impedance mismatch between the suspended particles and the suspending medium
2. Rough surfaces or heterogeneous media
What is the difference between power and intensity?
power is the rate at which the energy passes through a unit area. Intensity of a sound beam is the total power in the beam divided by cross sectional area of the beam.
What would be the PRP if the PRF is 8kHz?
0.125 millisecond (ms)
1 / 8kHz= 0.125 ms
PRP (ms) = _____1____
PRF (kHz)
The three terms that encompass attenuation and their definitions:
a. Absorption: Conversion of sound to heat
b. Reflection: Portion of sound returned from a media boundry
c. scattering: Redirection of sound in many directions by rough surfaces or heterogeneous media
a. Define the two types of imaging incidence:
b. Which type of imaging incidence is commonly observed is diagnostic medical sonography?
a. perpendicular incidence:Denotes a direction of travel of the incident ultrasound wave to a boundary between two media
Oblique incidence:Sound direction that is not perpendicular to media boundaries
b. oblique incidence
what is the equation for Spatial Pulse length (SPL)
SPL (mm) = wavelength (mm) × Number of cycles in the pulse
what are the 2 terms used to describe the strength of a sound?
Define both of the terms.
amplitude: maximum variation that occurs in an acoustic variable
intensity: the rate at which energy passes through a unit area.
If we know that ultrasound travels at a speed of 1540 m/s, what would be the frequency of a wavelength measuring 0.3mm
5.13 MHz
1540 m/s= 1.54 mm/µs
1.54 mm/µs / 0.3mm = 5.13 MHz
Pulse Wave (PW) sound is described using what terms?
Pulse repetition frequency
Pulse repetition period
pulse duration
Duty factor
spatial pulse length
bandwidth
1. Define refraction:
2. What type of artifact is observed with refraction?
3. Which type of incidence does refraction not occur?
1. a change in direction of sound when it crosses a boundary
2. Lateral position artifact
3. Perpendicular incidence
What is the Duty factor equation
DF= PD (us) x PRF (kHz) / 1000 (kHz / MHz)
1. Define attenuation:
2. Decibels are used to quantify?
1. The weakening in amplitude and intensity of sound while it propagates
2. Attenuation
What would be the Duty Factor if the pulse duration is 2us, and the pulse frequency is 4.3 kHz?
0.86%
DF= PD (us) x PRF (kHz) / 1000 (kHz / MHz)
DF= 2us x 4.3kHz / 1000 (kHz / MHz)
DF= 8.6 / 1000 = 8.6 x 10^-3
DF= (8.6 x 10^-3) x 100 = 0.86%
CW Sound is described by terms that are used to describe all waves, what are these terms?
frequency
period
wavelength
Propagation speed
amplitude
intensity
1. define spatial length
2. define bandwidth:
3.Sound is a mechanical compression of back-and-forth parallel motion to the direction of wave travel; this is call ___________________ wave
1. the length of space that a pulse takes up
2. the range of frequencies contained in a pulse
3. longitudinal / compression