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
what are the thermal risks
time average, adn it is worst for spectral
how is the image reconstructed
delays taken along transducer to line up pulse wave. One row at a time, then moves along to fill up FOV
what are the assumptions with ultrasound
when broken there are artifacts
what do we assume about pulses
we assume they are on straight line with echoes
what do we assume about the echo
echo comes from single reflection
is the attenuation non-uniform or uniform
uniform
what are the characteristics of pulses
pulse is focused and small
what are the strengths of ultrasound
no radiation, live, easy, and lots of information, like flow
what are the weaknesses
no actual quantitative information about the tissue, it is all relative
what is spectral doppler
lots of information but 1 line (like A mode), and peak and mean velocity, decreased FOVm need to specify angle. Very high transmit frequency. 100 pulses
what is color doppler
it gives direction and average velocity, but no peak. Bigger FOV, and no need to specify angle, so not fully quantitative, 10 pulses total
what is power doppler
like color, but basically no information. Very sensitive, so good for vascularization of tumor
