CAL: Ultrasound, MRI and CT

Question 1

Details of small flat head ultrasound scanner?

Answer 1

• ~ 8MHz
• small contact area, small superficial areas
• eg. intercoastal spaces, feline heart, mediastinal masses, pleural fluid, feline abdo, eye

Question 2

Details of curvilinear us probe?

Answer 2

• ~ 3MHz
• broad curved footprint
• eg. abdo foal/large dog

Question 3

Details flat large us probe

Answer 3

• ~15MHz
• very high freq
• broad footprint
• small superficial anatomical structures
• eg. tendons and ligaments, muscle injury, skin, mammary gland

Question 4

What does frequency affect? What is this measured in?

Answer 4

• Depth of penetration

- MHz

Question 5

What does gain affect? Measured in?

Answer 5

• Brightness of whole picture

- dB

Question 6

Give egs. of ultrasound artefacts that may be seen?

Answer 6

> Far enhancement
- after a fluid filled structure (Anechoic)
- region of hyperechogenicity
Waterfall/curtain
- d/t gas bubbles eg. stuck to gastric mucosa
- reverberation within bubbles appears as vertical echogeneic streaks
mirror image
- across line of diaphragm etc.
- d/t reverberations again

Question 7

How can the brain be ultrasounded?

Answer 7

• open fontanelle (if skull suture lines not properly closed eg. yorkies, cavies)
• craniotomy

Question 8

What should you be able to see with the transducer at the left flank just caudal to last rib?

Answer 8

• spleen
• left kidney and adrenal
• aorta
• left ovary

Question 9

WHat can be measured with doppler? What is this useful for?

Answer 9

• peak velocity ~1m/s
• flow away from transducer
  > good for detecting
• v flow velocity eg. heart failure and pulmonary hypertension
• ^ flow velocity eg. damaged pulmonic valve thrombus/shunt PDA

Question 10

What does T1W MRI show?

Answer 10

• CSF dark (hypointense) fat bright
• differences in T1 relaxation time of protons
• SHORT relaxation times = high signal in T1W (bright)
  > cholesterol/lipid large molecules = short relax times
  > water = long, unless ^ protein

Question 11

What does T2W MRI show?

Answer 11

• CSF bright
• differences in dephasing of psinning protons
• local magnetic fields of large molecules -> short T2 relax times
• LONG T2 relax = hyperintense (bright signal)
• protons in water stay in sync for a long time so appear bright (long t2 relax time)