all modality numbers and equations Flashcards
velocity of sound wave =
speed = wavelength x frequency
a loss of 3 dB represents
a 50% loss of signal intensity (power)
“half-value” thickness for US
tissue thickness that reduces the US intensity by 3 dB (50% loss of power) is considered the “half value” thickness
Snell’s law
Snell’s law is as follows:
sin θ1/c1 = sinθ2/c2
Where:
θ1 is the incident angle and θ2 is the refracted angle
c1 is the speed of propagation in the first material and c2 is the speed of propagation in the second material
general rul of thumb for attenuation of US beam in soft tissue
0.5 (dB/cm)/MHz
what unit is used for impedance
Rayl
Thickness of the PZT is generally ______ the wavelength of the ultrasound produced.
Thickness of the PZT is generally 1/2 the wavelength of the ultrasound produced.
solve for spatial pulse length if n =3
matching layer is generally _______the wavelength of the ultrasound produced
matching layer is generally 1/4 the wavelength of the ultrasound produced
Near field length =
Near field length = D2/4wavelength.
higher frequency = longer near field
shorter wavelength = longer near field
bigger diameter of the transducer = longer near field
if 1/2 the length of the SPL is larger than the distance between two nodules:
will look like one big nodule
ideal angle of isonation
between 30-60
range equation
c/2
(speed/2)
Factor of “2” results from the fact that the total round-trip path length of an ultrasound beam includes the path from the transducer to the reflector and then back to the transducer.
what s the minimum required separation between two reflectors before they overlap
1/2 the spatial pulse length (# of cycles emitted per pulse by the transducer)
most US pulses contain how many wave cycles?
2-3 wave cycles
