US Flashcards
3 different types of probe
- linear probe
- curvilinear probe
- echo probe (phased array)
linear probe
- frequency
- scanning area
- probe of choice for
- freq: high freq -> maintain resolution, less penetration
- scanning area: limited to size of probe
- probe of choice for vascular access, soft tissue and MSK, venous compression studies
curvilinear probe
- frequency
- scanning area
- probe of choice for
- freq: low -> decrease resolution, increased penetration
- scanning: large area
- probe of choice for abdominal, retroperitoneal, OB/GYN
echo probe
- frequency
- scanning area
- probe of choice for
- freq: low
- scanning: smaller than curvilinear
- probe of choice for cardiac studies
attenuation definition
loss of US energy (weakening) as it moves through a medium, resulting in decrease intensity and amplitude
attenuation is determined by
frequency of the sound and the distance that the sound wave travels (increase freq and distance -> increase attenuation)
attenuation occurs by
- absorption - primary component of attenuation in soft tissue
- reflection
- scattering - if boundary between media is irregular, wave is reflected in a number of different directions (ex: lung tissue)
- refraction - redirection of part of the sound wave when it crosses from one medium to another (bends the US wave, like when dip pencil in water)
impedance definition
how much resistance US beam encounters as it passes through a tissue
impedance depends on
- density of tissue (increase density -> increase impedance)
- speed of the sound wave
common artifacts
- attenuation shadow
- scatter
- ring down
- acoustic enhancement
- reverberation
- mirror image artifact
attentuation shadow caused by
region behind dense structure appears dark since few sound wave propagate into and return from that region
ring down caused by
fluid trapped between gas bubbles
acoustic enhancement caused by
sound wave intensify as it passes through fluid, thus region deep to fluid filled structure appears brighter than surrounding areas
reverberation caused by? examples?
- cause: sound waves bounce back and forth between closely spaced, highly reflective surfaces
- ex: saline implant, metal needle, comet tails (caused by gas collection along pleura, peritoneum, or bowel wall)
mirror image artifact definition
produces false images of adjacent organ (ex: diaphragm and liver)
how to tell it is a mirror image
disappear and appear with changes in the position of the transducer
septic shock:
cardiac
IVC
aorta
- hyperdynamic L ventricle, narrow IVC, normal aorta
2. hypodynamic L ventricle in late sepsis, collapse IVC, normal aorta
cardiogenic shock:
cardiac
IVC
aorta
cardiac: hypodynamic L ventricle
IVC: normal
aorta: normal
hypovolemic shock:
cardiac
IVC
aorta
cardiac: hyperdynamic L ventricle
IVC: narrow/collapse IVC
aorta: ?AAA
obstructive shock (cardiac tamponade):
cardiac
IVC
aorta
cardiac: pericardial fluid
IVC: variable
aorta: normal
obstructive shock (PE):
cardiac
IVC
aorta
cardiac: dilated R ventricle
IVC: dilated IVC
aorta: normal
kidneys
- medial to liver on the R
2. surrounded by bright capsule and medulla, dark cortex
pancreas
- body lies anterior to splenic vein and SMA
2. head lies anterior to confluence of portal and splenic vein
aorta
dark structure in front of bright vertebrae
IVC
- oval structure L of aorta
2. changes shape depending on respiration
bladder
- uterus posterior to bladder
2. hypoechoic
heart chambers
- subxiphoid view - R side of heart closer to transducer
- long axis parasternal view - ventricles
- short axis parasternal - ventricles and mitral valves
- apical view - ventricles near transducer, R ventricles small than L ventricles
lung/ribs
- sliding sign
- A line reverberation, B line reverberation (comet tails)
- seashore on M-mode
- pleural line (bright line below the ribs)
- ribs (dark circles closest to tranducer)
- mirror image of liver
bone
- periosteum of bone - far field reverberation artifact
2. seagull sign - formed by articular structures
mm
appears dark
nerves
honeycomb effect - clusters of dark fasicles surrounded by bright epineurium and perineurium
tendon
- densely packed parallel fibers
- aisotropy - bright when beam is perpendicular to tendon, dark when beam at acute angle (can be mistaken for vascular structures so use both long and short axis)
cholelithiasis/gallstones
stone appears bright with shadow behind it
pneumothorax
- no sliding
2. bar code sign
intraperitoneal free fluid
dark areas in recess
- hepatorenal recess - dark b/w kidney and liver
- splenorenal recess - dark b/w kidney and spleen
- suprapubic recess - dark b/w bladder and uterus
flat IVC
completely collapsed, suggest intravascular volume depletion and low central venous pressure
