Ultrasound Practical Flashcards
How to ultrasounds work?
Electric field applied to piezoelectric crystal in the transducer causes it to vibrate, generating ultrasound waves
When sound wave encounters a change in tissue type/ density, some waves are transmitted, and others are reflected; this generates an image
What will high frequency ultrasound waves generate?
They have a shorter wavelength, and so produce a better image resolution but have less depth of penetration so can only be used to examine relatively superficial structures
What is the doppler effect?
Frequency of transmitted sound is altered as it is reflected from a moving object. Can be used to examine flow, for example in a blood vessel
What do the colours mean when using a doppler?
Blue = away Red = towards
How can you optimise images using 4 basic movements?
Pressure; minimise distortion, compressible veins vs non-compressible arteries
Align; move across skin surface, follow structures e.g. vessels, nerves
Rotate: twisting movements to get true short axis view
Tilt: rocking movement to obtain best possible view due to anisotropy
What will bone appear like on USS?
Hyperechoic periosteum with acoustic shadow below
Appearance of an artery on USS?
Anechoic, pulsatile, usually round
Appearance of a vein on USS?
Anechoic, non-pulsatile, compressible
Appearance of a nerve on USS?
Variable appearance. Generally circular or oval, with a hyperechoic outline and speckled interior. More proximal nerves have a predominantly hypoechoic interior because they contain less connective tissue
Appearance of a tendon on USS?
Difficult to differentiate from nerves
Follow course; if turns into a muscle = tendon
Appearance of muscles on USS?
Hypoechoic mass; may have visible striae or hyperechoic fascia
What is acoustic shadowing on USS?
When acoustically opaque structures (bone, heavily calcified vessels) if in line with the ultrasound beam, a dark shadow will appear behind it
What is post-cystic enhancement on USS?
Inappropriately bright area behind/ deep to a fluid filled structure (large blood vessels, cyst)
What is reverberation on USS?
Commonly occurs if there is a strongly reflecting interface close to and parallel to the transducer, often a needle, vessel wall or muscle fascia
