TV4001 - Ultrasonography

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Veterinary Medicine (Small animal veterinary medicine) Flashcards on TV4001 - Ultrasonography, created by Alinta Kalns on 22/03/2018.
Alinta Kalns
Flashcards by Alinta Kalns, updated more than 1 year ago
Alinta Kalns
Created by Alinta Kalns over 6 years ago
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Question Answer
What are sound waves? Longitudinal waves of compression and rarefaction
What is the normal velocity of sound in tissue? 1540 m/s
How does an ultrasound transducer work? Piezoelectric crystals convert electrical energy to sound energy
What is attenuation? Weakening of sound waves due to reflection and absorption Denser tissue = more attenuation
How does wave frequency influence sound depth? Higher frequency = less depth - more pixels hitting/reflecting off the tissue increases attentuation
How does wave frequency influence image resolution? Higher frequency = more pixels hitting/reflecting off the tissue = higher resolution
How does amplitude influence brightness? Higher amplitude = poorer far-field brightness and visibility
Define acoustic impedance Difference in densities between two tissue types Shown by an acoustic interface between each tissue
List tissue types in descending order of density Bone > Muscle > Liver > Blood > Water > Fat > air
How much attenuation do sound waves go in fluid? NONE - anechoic, transmits waves 30% acoustic interface reflection with soft tissue
What artifact does fluid produce? Acoustic enhancement
How much attenuation do sound waves undergo in bone? 80% reflection 20% absorbance
What artifact can be seen with bone? Anechoic acoustic shadowing - only see edge of structure
How much attenuation do sound waves undergo in air? None, 100% reflection of sound waves
What artifact is produced by air? Reverberation artifact
What types of resolution are there? Lateral - 2 structures adjacent, perpendicular to sound beam Axial - 2 structures behind one another, parallel to sound beam
What factors influence lateral resolution? Beam width Focal zone Transducer type Thinner width + linear transducer = better resolution
What does a curved beam do in lateral resolution? Produce merging artifact
What factors influence axial resolution? Pulse length Pulse frequency Shorter wavelength + higher frequency = better resolution
What are the ultrasonic modes? A-mode - Amplitude B-mode - Brightness M-mode - Motion Doppler - Velocity (spectral, colour, power)
What are the different transducer types? Liner - wide near-field Curvilinear/Convex - sector Phased array - sector Annular array - sector
What types of focus are there, and what does using more than 1 focal zone do to the image? Broad focus Multi-point focus (1-4) More focal zones decreases image quality
Track Ball Cursor movement +/- zoom
Power gain Changes amplitude of sound beam Creates whole-screen artificial enhancement
Time gain Left = echo suppression Right = echo enhancement Up is near-field, down is far-field
When would you use time gain? Pancreatitis is highly hyperechoic Near-field suppression needed to see far-field structures
When would you use split screen? To compare structures To measure a long structure
Image direction Changes left and right direction of the image
What is often used to set initial depth of an ultrasonic image? Magnification Liver is often used to start with
What ID do you need to include in an ultrasonic image? Patient ID and case number Organ ID Probe orientation Practice and date
Where could you stored ultrasonic images digitally? PACS system Hard drive Personal computer
Define anechoic. No returning echoes - homogenous E.g. fluid
Define hypoechoic Low intensity returning echoes Low reflection E.g. organs with high fluid content (kidneys)
Define hyperechoic High intensity returning echoes Large acoustic impedance
Isoechoic Two adjacent structures have the same echogenicity
Normoechoic A structure returning the expected echo intensity
How would you describe echoes? Homogenicity Artifact Borders/walls Adjacent echo patterns
Describe acoustic enhancement. Sound waves that travel through fluid and undergo no attenuation, causing the structure after the fluid to appear hyperechoic
Describe acoustic shadowing. Produced if sound waves encounter tissue with high reflection and absorption Anechoic area after said tissue
Describe edge shadows Narrow hypoechoic shadows produced by walls of cystic structures
What influences edge shadows? Refraction - difference in speed of sound in a structure vs surround tissue Reflection - angled incident beam
What is reverberation? 100% reflection - sound waves bouncing to and from transducer Multiple equidistant hyperechoic lines produced
What are 2 forms of reverberation? Comet-tail - solid hyperechoic streak due to metallic objects Ring-down - similar to comet-tail, produced by bugle-shaped fluid trapped between air
What can cause ring-down reverberation artifact? Pleural/interstitial disease Gas trapped in bladder
Describe mirror-image artifact Highly reflective, curved structure rebounds sound waves at an angle and tricks transducer into believing structures those waves hit are deep to the curved structure Positions it on a linear axis + the real image
Describe slice thickeness. Lateral resolution artifact Soft tissue included in fluid - average of both echoes taken, simulates sediment in fluid
How do you check whether slice thickness or true sediment? Ballottement of the structure
What are 4 operator artifacts? Poor patient preparation Poor transducer contact Incorrect gain settings Off-incidence artifact (not perpendicular to structure)
What factors would you use to describe a lesion? Radioopacity/echogenicity Size, shape, number, location, margination Homogenicity Useful artifact present Edge regularity + definition Surround tissues (effect on structure) Vascularity
How would you describe tissues on ultrasound? Tissue type + echogenicity Artifact Foreign bodies
What does gas produce when it moves over other structures? Curtain sign - incomplete acoustic shadowing
What would you expect if fluid become hypoechoic or hyperechoic? Crystalline or cellular content increase Suspended gas Food in lumen of GIT
What echogenicity is cartilage? Anechoic
How would you recognise musculature and tendons? Striated appearance Wavy/hypoechoic if not engaged
Name organs in descending organ of echogenicity Prostate > spleen > liver > kidney
Which organ is used as a reference for parenchymatous ultrasonography? Spleen - most homogenous + hyperechoic
What artifact does metal produce? Comet tail
What echogenicity is wood? Hyperechoic until absorbs fluid from body Acoustic shadowing if recent
What are echogenicities of the small intestinal wall layers? Mucosa - thick hyperechoic Submucosa - hyperechoic Muscular - hypoechoic Serosa - hyperechoic
What scanning planes would you normally adhere to? Sagittal Parasagittal Transverse
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