Chapter 2 Ultrasound - Notes 2
after the incident beam hits a border part of the beam is reflected back
after the incident beam hits a border part of the beam is transmitted through the next medium
the angle in which the beam is reflected back
reflected angle = incident angle
What does the intensity of the reflected beam depend on?
impedance = density * speed
resistance to sound traveling through the medium.
What is likely when turning up output gain?
What is the relationship between impedance and propagation speed?
What is the relationship between impedance and density?
% of the beam that is reflected back to the transducer
IRC formula 1
IRC = Reflected Intensity/ Incident Intensity
IRC - Ri/Ii
IRC formula 2
[(z2 - z1) / (z2 + z1)] squared
% of the beam that is transmitted through the medium
ITC formula 2
ITC = Transmitted Intensity/ Incident Intensity
ITC - Ti/Ii
IRC + ITC =
D) 0 dB
E) 10 dB
other names for 90 degrees
Impedance relationship with IRC
Bone will always appear _________ due to high impedance mismatch
change of direction of the sound wave as it passes from one medium to another.
Refraction transmission angle
angle of transmission depends on change in propagation speed that exists between two media
Sine i/ sine r = speed i / speed r
Snell's law 2
(New c / old c) * old angle = new angle
Is the angle higher or lower if the new speed is slower?
when sound waves hit a large smooth surface at 90 degrees
bladder and vessels
boundary is not smooth
boundary smaller than the wavelength.
Light gets scattered (random and disorganized)
non-specular reflection occurs at small, irregular of rough interfaces
It is not angle dependent
Relationship between frequency and scatter
Positive effects of scattering
scattering makes echo reception less dependent on incident angle
allows visualization of boundaries which specular reflection angle would miss
Effects of scatter
Two waves arriving at the same time either reinforce of cancel each other.
Negative effects of scattering
d = 1/2 ct
Distance can not be measured but time can if speed is known
How machine places image
How long will it take for u/s to detect a mass at a depth of 1 cm?