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Department
of Podiatry
Diagnostic
Ultrasonography
Real-time examination
Uses non-ioniozing, high frequency sounds to generate an image of
a particular structure
Use in foot and ankle becoming increasingly popular
relies on concept of Doppler ultrasound
Ultrasound transducer and equipment
Principles
of ultrasonography
Same as Doppler
Transducer with piezo-electric crystals
Sound waves transmitted into body
Waves interact with different tissues
Waves are reflected and return back to transducer (echo)
Returning echoes are displayed as dots of light on an oscilloscope
Position of dot corresponds to position in body where echo was generated
US image represents a cross-section of underlying anatomy
returning echoes converted to a grey scale
Are assigned 1 of up to 64 shades of grey
Resulting image shows boundaries between soft tissue structures and
internal structure
Higher the frequency of sound, the better the resolution of imaging
High frequency sounds are attenuated more rapidly in soft tissues,
so cannot penetrate very deeply
7.5 to 10MHz transducer
Uses of ultrasonography
Muscles, tendons, ligaments and vessels
Therefore; thrombophlebitis, tendon and muscle tears, hematomas, abcesses,
tumors, neuromas
Poor for bone lesions
Reading the image
Longitudinal and cross-sectional scans
Masses can be characterised by the number of echoes generated within
it
Echo free areas (hypoechoic); fluid
Echogenic; solid tissue, abscesses (sound is reflected)
eg. Achilles tendon rupture - peritendinous fluid accumulation, hypoechoic
pattern
Ultrasound of the popliteal region (to be added to this page)
Acute rupture of Achilles tendon
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Diagnostic
ultrasound: frontal plane view of the hallux
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Calcaneal
ultrasound: partial tear of medial fibres of the achilles
tendon. Arrrows indicate tear
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