Ultrasonography Flashcards
what does echogenic mean?
able to send back an echo (sound waves reflect off surface)
so shows a light area in an ultrasound scan
what does anechoic mean?
doesn’t send back an echo (sound waves do not reflect off surface)
so shows a dark area in an ultrasound scan
what does hypoechoic mean?
not many echoes are sent back
areas appear dark grey
eg. solid masses of dense tissue
what does hyperechoic mean?
appearance? examples?
lots of echoes are sent back
areas appear as light grey
less dense as hypoechoic tissues
eg air, fat, or fluid
how do ultrasounds produce an image?
1) electrical current is transferred into the transducer
2) the piezoelectric crystals within then become electrically charged and oscillate in the probe head
3) this creates ultrasonic soundwaves
4) via contact media the soundwaves are emitted into the tissues
5) some soundwaves will lose energy, continue through the body or hit dense tissue and reflect
-> positioning and echogenicity will dictate the degree of reflected soundwaves
6) the transducer calculates the time passed since a pulse was transmitted and received, then converts this into electrical signals
7) a computer then interprets the electrical signals to produce a real-time image
why is the angle of the U/S beam important?
a severe angle will cause refraction and poor reflection
- so changes the image produced
- it will also increase artefacts
high vs low frequency ultrasound
High Frequency
- more waves in a shorter time
- creates high-resolution image
- low depth availabilty
- used on superficial tissue - tendons/heart
Low Frequency
- less waves in a longer time
- high depth field - see structures in and around
- low-resolution image
- used on gall bladder/liver
best to balance
what are the key elements of a transducer?
electrical input
acoustic regulation
piezoelectric crystals
outlet
what different artefacts can you get on an ultrasound?
acoustic shadowing
- no data past a certain feature/tissue
- lack of signal deeper as soundwaves are reflected
- creates a shadow - not free fluid
- eg bladder stones
enhanced-comet tails
- when small hyperechoic objects are hit
- creates lines of light grey down the image
- eg interlobular thickening
mirror image
- when there is a highly reflective surface in the path of the primary beam
- creates a mirror image deeper into the tissue
- mainly with diaphragm
edge artefacts
- as soundwaves hit round objects they are reflected
- often transmitted deeper so often dont return
- makes edges badly defined
how do you overcome artefacts?
move the angle of the probe to try and get around any objects interfering with soundwaves to eventually see full view
what are the different types of ultrasound probes?
cardiac - narrow to fit into intercostal spaces
curved array - large image field for abdomen
liner array - narrow but high freq. - good for biopsies
endorectal - electrodes on lateral aspect - pregnancy scans
how should you prepare a patient for an ultrasound?
clip area
- hairs traps air = artefact
clean site
- as dirt is a barrier
add contact gel - water-based
- leave to soak for 5-10mins
- smoother application
- better contact and transitional aid
good restraint - type is patient dependent
what can you use ultrasonography for?
thorax/cardiac
- heart murmurs, thickening of the heart
- pneumonia - can cause enhanced comet tails
abdominal
- sensitive to changes in tissue density - see damage
- can see free fluid
- can measure features - eg stones, FBs, masses etc
- help make treatment decisions
pregnancy
- litter size and abnormalities
- also reproductive tract scanning - eg pyo
