Lecture 16

Question 1

What type of tissue is ultrasound most useful in evaluating?

Answer 1

Ultrasound is best for soft tissue strucutres and allows for evaluation of structures such as the adrenals, pancreas, lymph nodes and the uterus.

Question 2

Is fluid beneficial in ultrasound?

Answer 2

Yes. Fluids aids ultrasound. It is the enemy in radiography. (causes effacement)

Question 3

Is fat good in ultrasound? What imaging technique would it be good for?

Answer 3

Fat is bad in ultrasound. Good in radiogrpahy though.

Question 4

Provide an example of where ultrasound examination may be limited:

Answer 4

1. patient obesity
2. deep chested breeds
3. abdominal pain
4. panting a poor patient cooperation
5. Lack of an acoustic window
6. Poor patient skin surface

Question 5

What is the definition of one cycle of a sound wave?

Answer 5

a compression and a rarefraction

Question 6

Briefly explain the Piezoelectric principle (how ultrasounds are made):

Answer 6

1. Electric current is applied to the cystals which causes them to vibrate and emit a sound
2. Ultrasound then leaves and travels through the patient
3. At tissue plane some of the sound is then reflected back to transducer causing it to vibrate
4. Creates an electric current which is then recorded

Question 7

What determines the brightness of the dot on the ultrasound image?

Answer 7

The amplitude of the wave

Question 8

What is a frame rate, roughly what percentage of the time is spent recording the feedback?

Answer 8

A pulse listen cycle refers to the period of time between sending the signal (approx 1%) and the time receiving the signal back again (99%). Every time this refershes is one frame. The frame rate is the number of frame changes per second.

Question 9

What does a dot deeper in the image reflect?

Answer 9

A longer period of time to come back to the transducer.

Question 10

What three factors influence the strength of the returning echo?

Answer 10

1. The reflecting capacity of the interface
2. Angle of interface to the sound beam
3. Strength of beam after attenuation

Question 11

What is the name for the reflecting capacity at the tissue interface?

Answer 11

Acoustic impedance

Question 12

What factors influence acoustic impedance?

Answer 12

1. Velocity of the sound in the tissue
2. Tissue density

Question 13

a. Name this type of artifact?
b. What caused it?

Answer 13

a. This is a reverberation artefect
b. This is caused by a junction between soft tissue and air

Question 14

a. Name the type of artifact that is shown below?
b. What caused this artefact?

Answer 14

a. Shadowing artfect
b. Barrier soft tissue and bone

Question 15

What factors influence the angle of reflection?

Answer 15

1. Transducer angle to the patient
2. Transducer angle to the organ

Question 16

What factors influence the level of attenuation that occurs?

Answer 16

1. Depth
2. Tissue types passed through
3. Transducer frequency

Question 17

What is the rate at which attenuation occurs?

Answer 17

0.5 decibel per centimetre per megahertz (dB/cm/MHz)

Question 18

Differentiate between axial resolution and lateral resolution

Answer 18

Axial resolution is through the image depth whereas lateral

Question 19

For the images belown state which one was imaged at a higher frequency:

Answer 19

B- sharper image

Question 20

What is the impact of using a wide beam?

Answer 20

Very dificult to resolve strucutures if they are side by side.

Question 21

When would you want to use a linear array transducer?

Answer 21

Useful for imaging surface structures.

Question 22

What is a good transducer to use for the abomen?

Answer 22

A curvilinear array. Allows for better imaging of deeper structures.

Question 23

What transducer is best to use for a very deep wide field of view?

Answer 23

Phased array/mechanical sector