application of ultrasound Flashcards
what benefit does ultrasound have over many other imaging modalities
real time assessment
sonography is not a profession in its own right, in order to be registered they must hold a professional title
what are the 2 forms of ultrasound
standard
portable
what are the 2 types of portable ultrasound
- hand held connection to tablet or smart phone
- trolly or cart connected to laptop / laptop equivilant
static machines can vary in size and capability with a range of functions
smaller machines for single clinical settings
multifunctional amchinesas used in clinical imaging department
what are the 3 general components of ultrasound
display monitor
transducer/probe
internal memory for image storage
what are the 5 adjustable controls on the control panel of an ultrasound machine
- focus
- TGC
- gain
- depth
- zoom
what are the 3 different probe types and the shape of their beam
linear = rectangle
curvilinear = cup shape (curved following probe surface but still running parallel) wide near and far field
phased array = cone shaped, tip closest to probe and widening going out (narrow near field, wide far field)
what is linear probe good for
vascular small parts and intraoperative settings
whats curvilinear probe good for
deep structures e.g obstetrics
whats phased array prob good for
imaging through obstructions e.g ribs in cardiology
what position is the patient usually in for xamination
supine
what is acoustic couplant and why is it needed
gel, needed to transmit sound
how would you position the patient to scan musculoskeletal e.g shoulder
sit upright on bed or chair
what are the 2 main imaging modes
grey scale
doppler imaging
what is grey scale mode imaging
- use of grey scale imaging in ultrasound renders a two-dimensional image in which the organs and tissues of interest are depicted as points of variable brightness.
- has modes A, B, M
what are the 3 grey scale modes and what are they used to scan
A mode = simple ultrasound to measure distances (pulse echo)
(pinpointing structures)
B mode = bright mode, used for gaining 2d info (scanning plane)
M mode = motion mode, cardiology (excellent axial and temporal resolution)
what are the 5 modes of doppler imaging
continuous wave dopple
pulsed wave doppler
power dopple
colour dopple
duplex dopple
what is continuous wave dopple
- simultaneously transmits and receives sound waves with separate crystal elemennts
- displayed graphically as single line
what is pulsed wave doppler
selected small area in b mode image and only doppler shifts from this area is recorded
what is colour doppler
visualisation of flow direction and velocity within user defined area
what is power doppler
uses amplitude of doppler signal to detect moving matter
what 2 things is power doppler independent of and how is this beenficial
- independant of flow and velocity
- independent of angle
hence has higher sensitivity than colour doppler
what is duplex doppler
combines colour doppler image with 2d greyscale image
- allows more comprehensive analysis of blood flow and surrounding structures
what might you see on image from doppler US if there is acute thrombosis
- increased venous diameter
- soft intraluminar materia
- smooth surface
- free-floating edge
what are some general sightings from doppler US
- loss of phasic flow on valsalva manoeuvre
- absent colour flow if complete occlusion
- lack of flow with calf squeeze
- increased flow in superficial veins
- non compressible venous segment
how does bright mode imaging / B mode work
- sound waves emitted along axis of propagation
- returning echoes detected by transducer and converted into electrical signals
- electrical signal /voltage amplified and assigned various shades of grey pixels according to echo strength (acoustic impedance)
how does the signal strength affect the colour on image give example
strong signals = brighter pixels e.g bone
(as they are strong reflectors)
known as hyper echoic or echogenic (bright)
weaker signals = darker pixels (hypo echoic)
what is obstetrics and why is it used
pregnancy ultrasound used to assess progression of fetus
- number of foetus in womb
- gestation of fetus
- location of placent
- fetal position
- movement heart rates
- amount of amniotic fluid in uterus
what is FASP and when would this be done
The NHS Fetal Anomaly Screening Programme
- done around 20th week of pregnancy as that is when structural anomalies begin to show
what are the 2 ways that a pregnancy scan is done
trans-vaginally (early stage)
trans- abdominally (in 2nd 3rd trimester)
why might doppler ultrasound be used in obstetrics
- to measure blood flow to umbilical cord and uterine artery is theres suspicion that fetus is not growing properly from growth measurements
3D/4D ultrasound only done for ‘keepsake’ purposed
what is gynaecology and what is it used for
pelvic ultrasound or transvaginal ultrasound used to diagnose growths, tumours of ovary, uterus and Fallopian tubes
what is GMUS scan and what sturctues are usually scanned
general medical ultrasound
- abdomen
- liver
- gallbladder
renal system
what is a renal ultrasound used for
evaluate function and structure of kidneys
- can assess size and shape of kidneys too
what are the 3 limitations to using US/ what 3 procedures would u not used US for and why
- organs obscured by bowel (air and gas disrupts US waves via scatter)
- obese patients (weaker signal when passing through more tissue) (also absorption and scattering)
- internal structure of bone (cannot fully penetrate due to acoustic impedance but you can assess small fractures)
