C4: Pulsed Ultrasound Flashcards
what are the 5 wave parameters for a pulsed US system
pulse duration spatial pulse length pulse repetition frequency pulse repetition period duty factor
what is pulse duration
formula?
time it takes for one pulse to occur, this does NOT include dead time
PD = T x RD (cycles in a pulse)
what is spatial pulse length
formula?
the length of the pulse
SPL = lambda x RD
what is pulse repetition frequency
formula?
number of pulses emitted in one second
PRF = 1/PRP
or
PRF = c/D
what is pulse repetition period
formula?
time from the beginning of the pulse, to the beginning of the next one….
…. it is another way of expressing Go-return time (PRP is the ‘t’ of the range equation)
PRP = 1/PRF
or
PRP = D/c
what is duty factor
formula?
% of time the crystal is ringing
DF = (PD / PRP) x 100
how does SPL effect resolution
shorter pulse = better resolution
does DF have units
no, its unitless
what 2 properties of a medium determine/effect acoustic velocity
density and compressibility
define density
the mass of a substance per unit volume, or the [ ] of matter
if all factors remain constant, how would an increase in density effect the rate of travel of sound
it would impede it (more mass per unit requires more energy to get through)
whats one factor has the greatest effect on velocity
compressibility
what is compressibility
how ‘squishy’ something is… or, the fractional decrease in volume when pressure is applied to the material
if a material is easy to compress, will sound have a slower or faster velocity as it travels through it
slower
how is density and compressibility related
inversely related (high density = low compressibility)
