Ultrasonography: Where to start? Tony Pease, DVM, MS Assistant Professor of Radiology North Carolina State University

Chapter 4 in Nyland/Mattoon 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 Gain = post-processing 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 With Harmonics 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 Higher number = better resolution Decreased penetration

Bottom line For canine abdomen For feline 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 Hyperechoic Hypoechoic Isoechoic Anechoic

Hypoechoic to hyperechoic 1. Bile, urine 2. Muscle 3. Renal medulla 4. Renal cortex 5. Liver 6. Fat 7. 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 Lateral recumbency Clockwise exam 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 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