Foundational Math
Say the equivalent decimal and percentage for:
1/20
0.05 or 5%
Name all acoustic variables
Pressure, temperature, density and particle motion.
A 4MHz transducer produces a sound pulse with frequencies ranging from 1MHz to 7MHz. What is the fractional bandwidth?
6/4 = 1.5
The speed of a 2Mhz continuous wave is 1.8km/s. the wave is then pulsed with a duty factor of 0.5.what is the new propagation speed.
1.8 because propagation speed is only affected by the medium
Define Fresnel Zone and list its other names.
Define Fraunhofer Zone and list its other names.
- The Fresnel Zone is the near field (between crystal and beam focus as the beam converges). It is also called the near field or near zone. Near zone length is this distance of this region.
- The Fraunhofer Zone is the far field (between the focused region of the beam and the end depth of penetration). It can also be called far field, or far zone.
The metric system is Giga, Mega, Kilo, Hecto, Deca, Deci, Centi, Milli, and Micro write their corresponding numbers
109 106 103 102 101 10-1 10-2 10-3 10-6 10-9
Frequency, period, amplitude, power, and intensity are all determined by
the sound source
The SPL in soft tissue for a two cycle pulse frequency of 5MHz is _____ mm.
2 x 1.54 / 5 = 0.6
With deeper imaging the listening time of the ultrasound machine increases. Thus the ____ also lengthens.
PRP Pulse repetition period
What is lateral resolution? List the other accepted names for this type of
resolution.
- Ability to distinguish between 2 side-by-side
objects and/or the ability to accurately determine the dimension of a
structure along the width of the beam (depth).
- Also called azimuthal, transverse, angular, or side-by-side
We assume propagation velocity to be ______m/sec
It takes ____usec to travel 1 cm
1,540
6.5, but 13 roundtrip (total of 2 cm)
Which of the following is/are true regarding waves
A. Mechanical waves must have a medium to propagate
B. Sound travels in longitudinal waves
C. In a transverse wave particles move parallel to thedirection of the wave propagation
D. Electromagnetic waves can travel through a vacuum but not through a medium
A. Mechanical waves must have a medium to propagate
B. Sound travels in longitudinal waves
If all other factors remain unchanged, what will happen to the duty factor when sonographer uses a new transducer with a longer pulse duration?
Duty factor increases
Define Intensity Transmission Coefficient (ITC)
ITC is the percentage of the intensity that continues forward when the sound
beam strikes the boundary between two media.
- In clinical imaging, most (99% or more) is transmitted at a soft tissue to
soft tissue boundary
- A much smaller percentage is transmitted when sound strikes a
boundary between soft tissue and bone or air
How does beamwidth impact lateral resolution?
Lateral Resolution is approximately equal to Beamwidth
Since the beamwidth changes with depth, the lateral resolution varies with the beam changes over depth. It should be best in the natural focus of the beam.
Finish the equations
Intensity = Power = __________
Intensity = Power / ________
(Amplitude)2
Area
Which type of waves will exhibit both constructive and destructive interference?
Waves of different frequencies
If the PRP is 700us and the pulse duration is 25us how much time is the machine listening?
675 microseconds
Define Intensity Reflection Coefficient (IRC)
IRC is the percentage of the intensity that bounces back when a sound beam
strikes the boundary between two media.
- In clinical imaging, very little (1% or less) is reflected at a soft tissue to
soft tissue boundary
- A much greater percentage is reflected when sound strikes a boundary
between soft tissue and bone or air
1. If two media have the same density but different propagation speeds, the one with the higher propagation speed will have the (higher or lower) impedance.
2. If two media have the same propagation speed but different densities, the one with the higher density will have the (higher or lower) impedance.
Higher & higher
Convert 10111 to a decimal
16+0+4+2+1 = 23
Calculate the wavelength in soft tissue using a 10 MHz transducer.
154 microseconds
What sound parameter in diagnostic ultrasound determines the penetration and resolution abilities?
Operating frequency
What 2 conditions must exist for refraction to occur?
For refraction to occur, there must be oblique incidence and the media must
have different propagation speeds.
Snell’s Law quantifies and predicts ______.
refraction