ultra sound first set of questions made by class Flashcards Preview

ultrasound > ultra sound first set of questions made by class > Flashcards

Flashcards in ultra sound first set of questions made by class Deck (56)
Loading flashcards...
1

Why do we use phased array?
a) To minimise heat
b) To steer the beam of sound
c) To change AC – DC
d) To reduce artifacts

b) To steer the beam of sound

2

How do you control the shape of the beam being produced?

Change the focus of the beam

3

What does TCG stand for?

Time gain compensation

4

What does A stand for?

Amplitude

5

What does focus control?
a) Penetration depth
b) Region of best resolution
c) Enlarges ROI
d) Pulse repetition frequency

b) Region of best resolution

6

When does refraction occur?

Deviation is in the path of a beam, it occurs when the beam passes through interfaces between tissues of differing speeds of sound, when the angle of incidence to an interface is not 90o

7

As the pulse travels through the body it loses energy due to what?

Backing material

8

What are the 6 steps for processing?

1. Detection
2. Preamplification
3. Time gain compensation
4. compression
5. rectification and envelope detection
6. rejection

9

What will too much preamplification produce?

introduce excessive noise into the subsequent analysis

10

The machine is calibrated so that the speed of sound is what?

1540 m/s which is the speed of sound in soft tissue

11

What does the speed in which the pulse travels through the body depend on?

The tissue type e.g. fat muscle blood and bone

12

If rejection threshold is too low what happens?

leads to many echoes which don’t represent anatomy

13

We look at data through a what?

window

14

Name 2 advantages of A mode:

Very quick as only 1 pulse needs to be sent out
Can give a clear picture on the anatomical boundaries

15

Name 2 disadvantages of A mode:

Small amount of data means less to interpret
Only 1 dimensional

16

What takes longer to produce A or M mode?

M Mode

17

What type of pulse will produce a wide range of frequency’s?

Narrower pulses

18

Define the term axial resolution:

The ability to display small targets along the path of the beam as separate entities

19

Define pulse length and wave length:

• Pulse length is determined by number of cycles in one pulse and length of each cycle (ie: wavelength)
• inversely proportional to frequency (c=fλ) so higher frequencies generate shorter wavelengths and therefore shorter pulse lengths

20

What is a backing material made from?

epoxy resin with rubber powder embedded in the epoxy

21

What is a phased array used for?
a) Increase frequency
b) Steer the bandwidth
c) Decrease the signal
d) Steer the sound beam

d) Steer the sound beam

22

What is a transducer and what is its purpose?

transducer in an ultrasound instrument
changes electrical energy into sound energy, and it can change sound energy into electrical energy.

23

What do piezoelectric crystals respond to?

to an electric field by producing pressure

24

basic transducer consists of 3 main parts

1. The case
2. The crystal
3. The damping material – more on that soon

25

The input to a transducer is called what?

Signal

26

Electrical signal coming in to the transducer produces?
a) Sound at a different frequency
b) Stays at an electrical signal
c) Sound at the same frequency
d) Returning echos

d) Returning echos

27

Explain the superposition principal:

When more than one wave is present at a given point we can simply add the value of the waves together at that point

28

Why is coupling gel needed in USS examinations?
a) Decrease noise
b) Remove impedance difference
c) Lubrication to reduce friction
d) Increase impedance difference

b) Remove impedance difference

29

What is the chosen wavelength difference for the matching layer?

¼ wavelength

30

The longer the pulse the ……………… the bandwidth.

Narrower