APEX Ultrasound Flashcards
How fast does US propogate into tissues? What about sound into bone?
1540 m/sec
3000-5000 m/sec
Frequency of sound wave
tells us the pitch
US frequency is range of 1-20 million far above the range we can hear
we can hear 20-20,000Hz
Wavelength of sound waves
peak to peak
higher frequency decreases wavelength
lower frequency produces longer sound wave
Amplitude
Sounds loudness in decibels
Modern US employ a piezoelectric material called ___
lead zirconate titanate
can transduce electrical energy to mechanical energy and vice versa
Vertical vs horizontal dot on the us screen
vertical- time delay
horizontal- the crystal it receives
Hyperechoic
white
high amplitude echos
bones
hypoechoic
grey
low amplitude
liver, skin, adipose, cartilage
anechoic
black
no echo
cysts, ascites, vascular ascites
absorption us
waves are lost to heat
reflection us
sound wave bounces off a tissue boundary
scatter ultrasound
sound wave encounters object smaller than the wave
refraction us
bending of us that encounters a tissue boundary at an oblique angle
Axial resolution
beam depth
improved by using a higher frequency
5/6 good
7/8 bad
Lateral resolution
Beam width
1 and 2 good
3 and 4 bad
Evaluation resolution
beam thickness
3 zones in us beam
near
focal- best resolution z axis
far
attenuation us
sound waves lose strength as it goes further into the body
this will decrease image quality
bone>soft>fluid
most to least attenuation
the result of 4 processes: absorption, reflection, scatter, refraction
Short axis
looks in cross section
what you see in us iv machine
long axis us
looks along the length
When to use high vs low freq us
high- shallow organ with high res
low- deep organ w low res
Different types of transducers
linear-flat- for organs with same width as transducer, accurate representation on screen
phased array-short- for deep organs
curvilinear- curved- signal is narrow on top but widens as it gets deeper
Which setting controls strength of returning echoes
gain
Depth US
how deep u can see into body
