Ultrasound Flashcards
what property does ultrasound measure
it is from the reflective properties of the tissue
how is the signal produced
piezoelectric crystal sends out pulses, and ultrasound pulses reflect off interfaces, and same crystal picks up reflected signal
what are the key formulas for ultrasound
o λ = c/f
o z = ρ*c
o power = dE/dt
o ΔP = 20log (P2/P1)
how do you calculate intensity
o intensity = power/A = Amplitude^2/A
o ΔI = 10log(I2/I1)
how do you find reflection
Reflection = [(Z2-Z1)/(Z1+Z2)]^2
how do you find near and far field
o Near field = d^2/4λ
o Far field = sin^-1(1.22λ/d)
what is the formula for doppler
Doppler: v = fdc/2fi*cosθ
what are the key components of the ultrasound system
probe, beam former, receiver, scan converter
what are the types of receivers
TGC, log compression, rectification, envelope
what are the types of scan converters
memory recon, storage, post-processing
what parameters do we control
FOV, depth, sampling, pulse repetition frequency, transmit frequency, doppler angle, spatial pulse length
what are the measures of image quality
spatial resolution
what is axial resolition
it depends on SPL, as short as possible
lateral resolution
depends on beam width and depth
elevational resolution
mechanical focusing and is the most difficult
what is temporal resolution
it is frame rate and depends on time for signal to get back
what is A mdoe
echo intensitty over time
what is B mode
B mode is a picture
what is M mode
it is movement. It is how points move in space with time
how do parameters affect image quality
increased FOV, depth, and sampling a decreased frame rate.
what happens if there is a decreased doppler angle
increased shift
what are the key tradeoffs with ultrasound
frame rate vs. sampling
depth, FOV
what are the risks of ultrasound
no risk to diagnostic ultrasound
what are the mechanical risks
pulsed average and wrost for color
