Diagnostic radiology - Ultrasound Flashcards
List organs/ structures that can be assessed by US
- GI: Liver, kidney, pancreas, gallbladder
- Heart: echocardiogram
- Pelvic: reproductive organs: uterus, ovaries, vagina…etc
- Blood vessel (color doppler)
- Thyroid and breast
- Guide biopsy e.g. FNAC
Frequency of ultrasound?
1 - 20 MHz
Inaudible to human ears
Principle of US physics
- Sound pulse transmitted into body and reflected back to encounter tissue interface
- Strong reflectors (e.g. bone) appear white on US
- Weak reflector (e.g. fluid filled organ) appear grey or black
3 main types of US transducers and function?
3 special transducers?
1) Convex = abdomen and pelvis
2) Linear = superficial and vascular structure
3) Endocavity = uterus, ovaries, prostate, rectum
Special:
- Transesophageal for cardiac US
- Endoscopic for stomach or duodenal US
- Endoluminal for endovascular or ureteric US
Indication for doppler US?
Assess vessels:
- Carotid arteries
- Limb vessels
- Liver, kidney, mass blood vessels
Advantages of US? (4)
- Non-ionising
- Quick
- Cheap
- Easy to perform
Disadvantages of US? (4)
- Cannot penetrate air, fat or bone well
- Operator dependent (to interpret)
- Small region of interest (limited view) compared to CT or MRI
Define the cause of artefacts:
- Acoustic shadowing
- Comet tail
- Ring-down artefact
- Posterior enhancement
- Acoustic shadowing = Large calcified masses
- Comet tail = small calcified masses
- Ring-down artefact = Gas bubbles
- Posterior enhancement = Fluid
Which plane US is used to view kidney?
Saggital
Term used to describe appearance of fluid (black) on US exam?
Anechoic
Effect of frequency on resolution and penetration of US
High frequency = better resolution but lower penetration
What artifact is seen behind a cavity of fluid on US?
Posterior enhancement
Artifact seen behind a large gallstone on US?
Acoustic shadowing
US Artifact seen behind small, tiny calcified masses?
Comet-tail artifact
What causes ring down artifacts on US?
Gas bubbles
- A horn or bulge shape fluid collected with gas bubbles surrounding it
