Knobology and U/S DSA Flashcards
What does POCUS stand for?
Point Of Care Ultrasound
What is the goal of a point of care US and where is it done?
done to answer a specific question - is there a pericardial effusion? etc.
done in office or at bedside by the provider
What are the 2 disadvantages of POCUS?
operator dependent
limitations - poor image quality with fat and/or air
How do US probes work, in general?
probe contains crystals like quartz
electrical current is applied to the crystals causing them to vibrate –> vibrations create sound or pressure waves
waves travel out from probe and hit object –> reflect back from object toward probe –> electrical current from sound waves is converted into an image
what is the unit for frequency in US?
Hertz (Hz)
one hertz = one wave cycle per second
How are wavelength and frequency related?
inversely
the higher the frequency the shorter the wavelength
higher freq waves don’t penetrate deeply into tissue
What are low and high frequency probes good for?
low: long wavelengths, penetrate deeply but poor resolution; used to image abdominal structures (aorta, kidney, gallbladder)
high: short wavelengths, good resolution for superficial structures (blood vessels, breast tissue, thyroid tissue)
what are linear probes for?
superficial scanning and procedural guidance
higher freq and resolution
preserved lateral resolution
What are sector or phased array probes for?
small footprint for intercostal scanning
lower frequencies, high frame rates
What are curvilinear probes used for?
abnominal or curved array
even lower frequencies, large field of view
large footprint
What does the FAST acronym stand for?
What is its purpose?
Focused Assessment with Sonography for Trauma
to detect free intraperitoneal fluid, pericardial fluid, pleural fluid, hemothorax, and pneumothorax in trauma pts
What is the limitation of FAST?
limited sensitivity precludes use of ultrasound as a definitive test to rule out intraabdominal injury
Where is Morrison’s pouch and what do you look for there?
RUQ at the edge of the lateral thoracic cage
can see the diaphragm, liver, kidney
if trauma would see fluid accumulate here btw the liver and kidney
Anechoic
complete absence of returning sound waves
appears black = fluid
hypoechoic
structures that have very few echoes and appear darker than the surrounding tissue
hyperechoic
echogenic structures, appear brighter than the surrounding tissue
acoustic shadowing
common artifact
occurs when the sound waves encounter a highly reflective surface
hypoechoic or anechoic area appears deep to the structure
occurs bc very few waves can get behind or around the structuer (gallstones)
Posterior acoustic enhancement
common artifact
occurs deep to an anechoic structure - which stuff behind black anechoic blob
ex. bladder
edge artifact
sound is bent by a structure in parallel w/ the US beam and doesn’t return to the probe –> shadow behind the surface
generally seen when imaging fluid-filled structures
mirror artifact
you see the “mirror image” of the structure imaging
it will be distal in relation to the probe
generally appears at the bottom or periphery of the screen
highly reflective surface causes the machine to display and artefactual image of the reflection of an object
reverberation artifact
typically seen w/ line placement
multiple intermittent lines “echoes” running parallel to the actual needle
rocking or heel-toe probe movement
tilt the probe along the axis of the indicator
fanning or “sweeping” probe mvt
tilt the probe perpendicular to the axis of the indicator
rotating or twisting probe mvt
rotate the probe about the axis of the cord w/out tilting
sliding probe mvt
move probe along the skin w/out changing angles
What is ALARA as it pertains to U/S?
As Low As Reasonably Achievable exposure
despite numerous studies, diagnostic US has never been shown to harm humans
safe for fetal imaging at all gestational ages as well
still practice ALARA just in case
How are longitudinal and transverse scanning done?
longitudinal: probe marker toward the head
transverse: probe marker facing the pt’s right so that the image will look similar to the orientation of a CT scan
*exception is cardiac = screen marker is on the left
What are the 3 tips to get the best US scan?
preparation - lights are dim, machine and pt are ready
preset - start w/ preset settings for structure you’re trying to image
image optimization - adjust image for every scan; adjust depth and gain to put image in center of screen
