75. ULTRASOUNDS: RECEIVERS

Question 1

1. What is the purpose of the receiver?

Answer 1

• it detects the signals
• it amplifies weak signals
• these signals come from different depths

Question 2

2. What do different tissue thicknesses attenuate?

Answer 2

• they attenuate different variations of Ultrasounds
• this means that they produce echoes of different
  strengths

Question 3

3. How do we make up for the difference in echo strength?

Answer 3

• we use the Time Gain Compensation (TGC)

Question 4

4. How would we amplify lower signals that come from deeper inside the body?

Answer 4

• we would make use of the Time Gain Compensation
  (TGC)
• this will correct the echoes
• this improves the image quality

NB:
- these lower signals have a higher frequency

Question 5

5. What can be said about the Time Gain Compensation in this image?

Answer 5

• here we have a Time Gain Compensation that is too
  low

Question 6

6. What can be said about the Time Gain Compensation in this image?

Answer 6

• here we have a Time Gain Compensation that is
  corrected

Question 7

7. What relation exists between the Attenuation of Sound and the Frequency?

Answer 7

• they are proportional
• they are constant for certain tissues

Question 8

8. What needs to be done to weaker echoes?

Answer 8

• weaker echoes return from deeper tissues
• they must be amplified more
• this produces a uniform appearance of the organ in
  question

Question 9

9. How can a weaker echo be more amplified?

Answer 9

• the operator can make use of Time Gain
  Compensation controls

THESE CONTROLS WILL:
- selectively amplify from deeper structures
- suppress the signals from more superficial structures

Question 10

10. What does the Time Gain Compensation impact?

Answer 10

• it impacts the quality of the image

EXAMPLE:
- high frequency transducers have higher attenuation
- they are used to image more superficial structures
- they produce very bright signals
- the image is too white
- the signals need to be suppressed by the TCG

Question 11

11. What do the receivers do to the Data that they receive?

Answer 11

• they compress and remap the returning data
• they compress it into an allowable dynamic range
• this range can be seen on a grey-scale display

Question 12

12. What is the difference between the dynamic range and the actual range of the reflected signals?

Answer 12

THE ACTUAL RANGE:
- can vary widely

THE DYNAMIC RANGE:
- can be more limited

Question 13

13. Why do Receivers selectively amplify returning signals?

Answer 13

• they do this so that the signals can match the Dynamic
  Range of the display