Resolving Phase Ambiguity in Pulsed Doppler Ultrasound

In summary, the conversation discusses the principle behind Pulsed doppler ultrasound and the issue of extracting phase information by repeating the process of transmit-echo-transmit-echo. An analogy is used to explain the problem and the concept of ambiguity in measuring distance and velocity using frequency and phase.
  • #1
BobP
74
1
Hi.
I understand the principle behind Pulsed doppler ultrasound. If the echo from a transmit pulse is sampled (gated) during a narrow fixed time period, the echo will correspond to a particular depth. What I do not understand is how we can extract phase information by repeating the process of transmit-echo-transmit-echo over and over again.

Here is why (I am going to use an analogy to explain my problem).
If we have a door that is moving away from us then if we transmit-recieve-transmit-recieve... then each time we transmit our signal the door will be slightly further away so it will take longer to receive the reflection. Hence we get a phase shift.

If however we have a stack of thousands of doors flowing along a line and we measure the reflection from a distance, d, from our transmitter (as we do with pulsed ultrasound) we will be receiving the reflection from a different door each time (we are not following a single door) hence there should be no phase shift as the reflection will occur at the same time, each time.

Is my problem clear?
Thanks for your help
 
Physics news on Phys.org
  • #2
BobP said:
Hi.
I understand the principle behind Pulsed doppler ultrasound. If the echo from a transmit pulse is sampled (gated) during a narrow fixed time period, the echo will correspond to a particular depth. What I do not understand is how we can extract phase information by repeating the process of transmit-echo-transmit-echo over and over again.

Here is why (I am going to use an analogy to explain my problem).
If we have a door that is moving away from us then if we transmit-recieve-transmit-recieve... then each time we transmit our signal the door will be slightly further away so it will take longer to receive the reflection. Hence we get a phase shift.

If however we have a stack of thousands of doors flowing along a line and we measure the reflection from a distance, d, from our transmitter (as we do with pulsed ultrasound) we will be receiving the reflection from a different door each time (we are not following a single door) hence there should be no phase shift as the reflection will occur at the same time, each time.

Is my problem clear?
Thanks for your help
If a Doppler radar uses frequency to find velocity there is no ambiguity. If the radar measures phase, it can find distance, but there will be an ambiguity if the velocity creates a phase change of more than one cycle for each pulse. So it is for stationary or slow moving targets.
 
  • Like
Likes BobP

1. What is pulse-wave Doppler ultrasound?

Pulse-wave Doppler ultrasound is a medical imaging technique that uses sound waves to produce images of blood flow in the body. It is a type of Doppler ultrasound that measures the velocity and direction of blood flow by sending and receiving sound waves at specific intervals.

2. How does pulse-wave Doppler ultrasound work?

Pulse-wave Doppler ultrasound works by emitting high-frequency sound waves into the body through a handheld device called a transducer. These sound waves bounce off of moving blood cells and are then detected by the transducer, which creates a visual representation of the blood flow.

3. What are the benefits of using pulse-wave Doppler ultrasound?

Pulse-wave Doppler ultrasound has several benefits, including its non-invasive nature, real-time imaging capabilities, and ability to provide information about blood flow and velocity. It is also safe, painless, and does not use ionizing radiation, making it suitable for repeated use.

4. What can pulse-wave Doppler ultrasound be used to diagnose?

Pulse-wave Doppler ultrasound can be used to diagnose a variety of conditions, including heart disease, blood clots, and vascular disorders. It is also commonly used to assess the function of the heart valves and to monitor blood flow during pregnancy.

5. Are there any risks associated with pulse-wave Doppler ultrasound?

Pulse-wave Doppler ultrasound is generally considered safe and does not pose any significant risks. However, in rare cases, it may cause mild discomfort or irritation due to the application of the transducer on the skin. It is important to follow the instructions of a trained medical professional when undergoing a pulse-wave Doppler ultrasound procedure.

Similar threads

  • Mechanics
Replies
5
Views
2K
Replies
0
Views
678
Replies
4
Views
3K
  • Introductory Physics Homework Help
Replies
2
Views
1K
  • Introductory Physics Homework Help
Replies
7
Views
2K
  • Special and General Relativity
Replies
2
Views
1K
  • Optics
Replies
10
Views
3K
  • Electrical Engineering
Replies
4
Views
2K
  • Special and General Relativity
Replies
20
Views
1K
  • General Math
Replies
4
Views
2K
Back
Top