Ultrasound

Question 1

How is an ultrasound image produced?

Answer 1

• Sound waves are transmitted into the body
• Some tissues reflect waves and some transmit them into deeper levels
• Reflected waves are used to make an image using the piezoelectric effect

Question 2

What is attenuation?

Answer 2

• Transmitted waves will lose energy as they pass deeper into tissues and eventually become too weak to form an image

Question 3

What are the two tissue types regarding echogenicity?

Answer 3

• Hyperechoic = causes increased reflection, so whiter image e.g., diaphragm
• Hypoechoic = causes decreased reflection, so darker image e.g., kidney, spleen and liver
• Anechoic = no reflection, so black e.g., bladder

Question 4

Describe a linear array transducer

Answer 4

• Produces a rectangular image using piezoelectric crystals that are arranged in a line
• Good resolution of superficial tissues
• Used for large animals

Question 5

Describe a convex array transducer

Answer 5

• Triangular, fain-shaped image produced using piezoelectric crytals that are clustered together
• Good resolution of deeper tissues

Question 6

Describe a phased array transducer

Answer 6

• Triangular, fan-shaped image produced using piezoelectric crystals that are closely grouped together and fire in sequence
• Useful for small spaces and cardiac imaging

Question 7

Describe a small-footprint linear transducer (hockey stick)

Answer 7

• Uses high frequency to produce very clear images of small superficial structures such as nerves

Question 8

Describe a endocavity transducer

Answer 8

• Used inside the body directly on the surface of organs to produce a wide field of internal structural view

Question 9

What are the potential risks to the patient when performing ultrasonography

Answer 9

• Mechanical injury due to tissue vibration and formation of bubbles in gases
• Thermal injury, as bone absorbs US heat and the probe can also overheat

Question 10

What are the potential risks to the sonographer when performing ultrasonography?

Answer 10

• Patient aggression
• Eye strain
• Arm or neck strain
• Slips and trips

Question 11

How should the patient be prepared for ultrasonography?

Answer 11

• May need to fast
• Sedation may be required
• Clip to remove hair, apply surgical spirit to degrease site and use ultrasound gel; this will remove the space for air to fill so better contact

Question 12

What are the 2 basic modes?

Answer 12

• B mode (brightness): 2D cross sectional view
• M mode (movement): single scan line

Question 13

What are the doppler modes?

Answer 13

• Detects movement of fluids such as blood
• Colour doppler: shows direction of fluid in colour
• Spectral doppler: shows direction and velocity of fluid flow

Question 14

What is contrast-enhanced ultrasonography?

Answer 14

• Used to image blood flow in organs
• Gas filled microbubbles given IV
• Microbubbles reflect most waves giving good contrast
• Contrast media quickly cleared, as gas breathed out

Question 15

What are the uses of ultrasonography?

Answer 15

• Anatomy/physiology
• Point of care
• US guided biopsy/needle aspirate
• Pregnancy diagnosis

Question 16

What are ultrasound not useful for?

Answer 16

• Fractures and nervous tissue, as waves get reflected or absorbed by bone and none passes through
• Air filled structures, as all waves reflected at surface

Question 17

Name 5 comparison between an ultrasound and a X-ray

Answer 17

• US detect tissues/structures not visible on a X-ray
• US is dynamic
• US performed with minimal patient preparation
• US has no ionising radiation
• X-ray useful for bone, US reflected by bone

Question 18

What are some advantages of using ultrasound over radiography in pregnancy diagnosis?

Answer 18

• No radiation risk
• Earlier visualisation (10-22 days after mating)
• Heartbeats used to evaluate viability
• Estimate number of foetuses