Diagnostic Imaging

Question 1

What generates an ultrasound pulse?

Answer 1

Piezoelectric crystals when a current is passed through. If ultrasound pulse hits a crystal array, it forms a current that can produce an image.

Ultrasound can be reflected, be absorbed, transmitted or scattered.

Question 2

What does white on an ultrasound connote?

Answer 2

Bone - big difference in acoustic impedance, so is hyperechoic where all waves are reflected.

Air - lots of echoes reflecting back at air interface, as air has lower acoustic impedance so is hyperechoic.

Question 3

What does grey on an ultrasound scan connote?

Answer 3

Tissues - some difference in acoustic impedance so some reflection. Can be hyper or hypoechoic in relation to background.

Question 4

What does black on an ultrasound scan connote?

Answer 4

Fluid - no reflection. Wave continues to propagate and is transmitted. Is anechoic.

Question 5

Describe how to prepare to take an ultrasound scan.

Answer 5

1. Prepare area - clip, clean and apply gel.
2. Prepare machine and appropriate probe.
3. Basic controls of depth, gain, focal depth and doppler (colour superimposed on image to show the direction of blood flow and velocity).

Question 6

Describe the process of interpreting an ultrasound image.

Answer 6

1. Develop routine - location, probe, orientation, material types and colours.
2. Identify important features: size, shape, position, echogencity, margination, number.

Question 7

What are the advantages of ultrasound over radiology?

Answer 7

• Allows seeing fluid and soft tissues
• Dynamic
• Safer

Question 8

What does radiography involve?

Answer 8

X-rays produced by interactions of fast moving electrons across a vacuum to a metal target. depending on atomic number, density and tissue thickness, X-rays may be absorbed, transmitted or scattered.

Question 9

Describe the appearance of high, medium and low density matter in radiography?

Answer 9

High - metal, bone. More absorption, so few X-rays exposing film. White image.

Medium - soft tissue, fluid. Some absorption, so slightly more X-rays exposing film. Grey image.

Low - gas. Little absorption, so more X-rays exposing film. Black image.

Question 10

Describe how to view a radiograph.

Answer 10

1. Develop a routine
2. View: head to left = lateral projections, animal facing you = ventral dorsal projections
3. View in standard way: comment on film quality, identify species, estimate age

Question 11

What features are important to identify when viewing a radiograph?

Answer 11

• If size has increased or decreased
• Shape
• Position
• Opacity - indicating excess fluid, soft tissue, bone deposition, foreign material, gas accumulation or loss of normal tissue
• Margination
• Number