Knobology and U/S DSA

Question 1

What does POCUS stand for?

Answer 1

Point Of Care Ultrasound

Question 2

What is the goal of a point of care US and where is it done?

Answer 2

done to answer a specific question - is there a pericardial effusion? etc.

done in office or at bedside by the provider

Question 3

What are the 2 disadvantages of POCUS?

Answer 3

operator dependent

limitations - poor image quality with fat and/or air

Question 4

How do US probes work, in general?

Answer 4

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

Question 5

what is the unit for frequency in US?

Answer 5

Hertz (Hz)

one hertz = one wave cycle per second

Question 6

How are wavelength and frequency related?

Answer 6

inversely

the higher the frequency the shorter the wavelength

higher freq waves don’t penetrate deeply into tissue

Question 7

What are low and high frequency probes good for?

Answer 7

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)

Question 8

what are linear probes for?

Answer 8

superficial scanning and procedural guidance

higher freq and resolution

preserved lateral resolution

Question 9

What are sector or phased array probes for?

Answer 9

small footprint for intercostal scanning

lower frequencies, high frame rates

a.k.a. cardiac probe

Question 10

What are curvilinear probes used for?

Answer 10

abnominal or curved array

even lower frequencies, large field of view

large footprint

Question 11

What does the FAST acronym stand for?

What is its purpose?

Answer 11

Focused Assessment with Sonography for Trauma

to detect free intraperitoneal fluid, pericardial fluid, pleural fluid, hemothorax, and pneumothorax in trauma pts

Question 12

What is the limitation of FAST?

Answer 12

limited sensitivity precludes use of ultrasound as a definitive test to rule out intraabdominal injury

Question 13

Where is Morrison’s pouch and what do you look for there?

Answer 13

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

Question 14

Anechoic

Answer 14

complete absence of returning sound waves

appears black = fluid

Question 15

hypoechoic

Answer 15

structures that have very few echoes and appear darker than the surrounding tissue

Question 16

hyperechoic

Answer 16

echogenic structures, appear brighter than the surrounding tissue

Question 17

acoustic shadowing

Answer 17

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)

Question 18

Posterior acoustic enhancement

Answer 18

common artifact

occurs deep to an anechoic structure - which stuff behind black anechoic blob

ex. bladder

Question 19

edge artifact

Answer 19

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

Question 20

mirror artifact

Answer 20

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

Question 21

reverberation artifact

Answer 21

typically seen w/ line placement

multiple intermittent lines “echoes” running parallel to the actual needle

Question 22

rocking or heel-toe probe movement

Answer 22

tilt the probe along the axis of the indicator

Question 23

fanning or “sweeping” probe mvt

Answer 23

tilt the probe perpendicular to the axis of the indicator

Question 24

rotating or twisting probe mvt

Answer 24

rotate the probe about the axis of the cord w/out tilting

Question 25

sliding probe mvt

Answer 25

move probe along the skin w/out changing angles

Question 26

What is ALARA as it pertains to U/S?

Answer 26

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

Question 27

How are longitudinal and transverse scanning done?

Answer 27

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

Question 28

What are the 3 tips to get the best US scan?

Answer 28

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