Transcript Ultrasound Lecture 1 - North Carolina State University

Ultrasonography:
Where to start?
Tony Pease, DVM, MS
Assistant Professor of Radiology
North Carolina State University
Reading
Chapter 4 in
Nyland/Mattoon
or
Chapter 2 in Thrall
RELAX!
Objectives
• Machine
• Terminology
• Examination
Examination
• Image orients like
a radiograph
Ultrasound Pitfalls
• Technical demand on time and patience
• Non-specific change
– Tissue characterization yet to be realized
• Opening Pandora’s Box
– Multiple abnormalities but you may not known
the clinical importance
Fatal assumptions
• Speed of sound is an average
– 1540 m/sec
• All sound waves are assumed to be
created by a primary beam
Ultrasound Knobs
Power vs. Gain
• Power = preprocessing
– Controls energy given to the transducer to
regulate intensity of the sound wave
• Gain = post-processing
– Increases the overall brightness given to the
returning signal
Power
Gain
Time Gain Compensation
• Also called TGC
• Will adjust gain at different depths
• Helps make the image uniform
Time Gain Compensation
Beam and focal spots
Nyland, Small Animal Diagnostic Ultrasound
Focal Spot
Tissue Harmonics
• Ultrasound wave goes in
– 5 MHZ
• Transducer listens for a higher frequency
– 10 MHz
– This is generated by the tissue imaged
Harmonics Benefit
• Only goes through tissue once
– Less artifacts
• Penetrates better than 10 MHz
– But not as good as a 5 MHz wave
Without
Harmonics
With
Harmonics
Types of probes
Linear array
Curvilinear
Phased array
How does it work?
Nyland, Small Animal Diagnostic Ultrasound
What about MHz?
• Generally 1-13 MHz
• Multiple frequencies in one probe
– 1-4 MHz
– 5-8 MHz
• Higher number = better resolution
• Decreased penetration
Bottom line
• For canine abdomen
– Average size dog
• Use a 5-8 MHz probe
– Deep-chested dog
• Use a 3-5 MHz probe
• For feline abdomen
– Can use 10-12 MHz probe
Terms
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•
•
Hyperechoic
Hypoechoic
Isoechoic
Anechoic
Hypoechoic to hyperechoic
1.
2.
3.
4.
5.
6.
7.
Bile, urine
Muscle
Renal medulla
Renal cortex
Liver
Fat
Spleen
8. Prostate
9. Renal sinus
10. Vessel walls
11. Bone, gas
Everything’s relative
• Echogenicity is a comparison
Examination
• Abdomen
– No set protocol
• Thorax
– Echocardiograph
• Lateral
Abdominal Ultrasound
• Patient preparation
– Clip or alcohol
– Acoustic coupling gel
• Appropriate probe selection (MHz)
• Image optimization takes time
• May need to switch transducers or
change frequencies
Abdomen
• Dorsal recumbency
– Clockwise exam
• Lateral recumbency
– Organ approach
Ultimate goal
• Examine all organ systems
• Examine in a routine fashion
Liver/Gallbladder
Liver
Where we are
Stomach (dog)
Stomach (cat)
Left limb of pancreas
Spleen
Left kidney
Adrenal gland
Variability of adrenal glands
Canine left adrenal gland
Feline left adrenal gland
Aorta
Aorta
Urinary Bladder
Medial iliac lymph node
Right kidney
Right adrenal gland - Dog
Right adrenal gland - Cat
Right limb of pancreas
Mesenteric lymph nodes
Small intestine and colon
Intestinal layering
• Superficial to deep
– Serosal = White
– Muscularis = Black
– Submucosal = White
– Mucosal (thickest) = Black
– Mucosal-luminal interface = White
Uterus
Pregnancy
• Can see heart beat around 21 days
• Can see limb buds by 32 days
• Check for viability
Other uses
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Brain imaging
Laryngeal exam
Guided aspirates
Contrast studies
Thyroid gland
Ocular exam
Blood flow
Umbilicus
Ultrasound guided techniques
• Needle approximate 45 degree angle
• Use appropriate needle length for target
• Be mindful of surrounding vessels
Cystocentesis
Fine needle aspirate