Chapters 1-3
What type of wave is sound in diagnostic ultrasound?
A mechanical, longitudinal wave
What is the most relevant intensity for bioeffects?
SPTA (Spatial Peak, Temporal Average)
What converts electrical energy into sound energy?
The piezoelectric element
What display mode uses upward deflections to represent amplitude?
A-mode
With B-Mode, which axis is related to the strength of reflection?
The z-axis is related to reflection strength
What determines the speed of sound in a medium?
The medium’s stiffness and density
What percentage of sound reflects at a soft tissue–air boundary?
Nearly 100%
What part of the sound beam is the narrowest?
Focus
What type of transducer steers the beam mechanically?
Mechanical transducer
With A-mode, what is displayed on the x axis?
Depth of the reflector.
What are the five main parameters of a sound wave?
Period, frequency, amplitude, power, intensity
What causes refraction to occur?
Oblique incidence and a difference in propagation speeds
How can axial resolution be improved?
Use higher frequency transducers (shorter SPL)
What mode provides a two-dimensional cross-sectional image?
B-mode
Which transducer created a rectangular shaped image?
Linear sequential array
What is the reciprocal of PRP?
Pulse repetition frequency (PRF)
What is the time of flight for a reflector located 1 cm deep?
13 μs
What are three consequences of backing material?
Decreased sensitivity, decreased ringing, increased bandwidth
In M-mode, what does the horizontal axis represent?
Time
In linear phased array, what is the firing pattern that steers a beam to the left or right?
electronic slope
What happens to intensity if amplitude is doubled?
Intensity increases by a factor of 4
If PRF increases, what happens to maximum imaging depth?
It decreases
What material is typically used as the active element?
Lead zirconate titanate (PZT)
What type of array has elements arranged in concentric rings?
Annular Array
In linear phased arrays, what is the firing pattern that focuses a sound beam?
electronic curvature