Adams: Ultrasound Flashcards
Why does longer listening time give you better resolution?
Imagine a cave with an echo
The more you yell the less you can hear reflected back and what you hear back is garbled. (long SPL and short listening phase)
Yell one word and the listen. (short SPL and long listening phase)
If higher signal frequencies provide better axial resoluation why not use hte highest freq possible at all times?
less penetration
High density
good transmission of sound
Low density
poor transmission of sound
Bladder
can see wall through water
Lung
can’t see well through air, just see artifacts (can diagnose CHF, pneumonia)
Flexible
Liver- good transmission of sound
Stiff
Bone
poor transmission of sound
What is the linear scanning format?
Straight box appearance
probes go straight through
Used for: things w/in 1-2 inches of surface neck vein in arm abscess central line testicles foreign body
HIGH freq so DONT penetrate
What is a sector scan?
Low frequency (2-4) BETTER penetration, but lose resolution starts close and spreads out
Something father away has to be bigger to be seen
Round footprint, flat footprint
What is gain?
controls the amt of brightness on the screen
How does a gallstone appear on ultrasound?
hyperechoic (gallstone) leaves a shadow below since most of the ultrasound waves have been reflected
HIGH GRAY SCALE
What do you use to measure a cyst in the liver?
medium gray scale
LIVER
What is used to ultrasound a fluid filled bladder?
low gray scale–anechoic
What mode do you usually use?
B mode
presents real time image
When is M mode used?
fetal heart tones
use one beam and measure that beam over time. allows you to see opening and closing of valves. less ultrasound exposure for baby.
What is a mirror artifact?
reflection seen when you’re over the diaphragm and the liver
Black on an ultrasound is indicative of…
fluid
What are the two rules of orientation?
- the TOP of hte viewing screen is always where the transducer is touching the patient
- the orientation marker on the transducer and on the viewing screen ALWAYS pt in the same direciton
What is ultrasound good for in kids?
diagnosing appendicitis
*should do before CT
