Jingzhi Li, MD; John Eisenbrey, PhD; Andrej Lyshchik, MD, PhD

KEY FACTS

Terminology
Basic Imaging Considerations
Physiology

TERMINOLOGY

Abbreviations
- Continuous-wave Doppler (CWD)
- Pulsed-wave Doppler (PWD)
- Peak systolic velocity (PSV)
- End diastolic velocity (EDV)
- Mean velocity (MV)
Synonyms
- Spectral Doppler imaging
- Range-gated Doppler
Definitions
- US images of spectral Doppler flow are obtained from measurements of movement by transmitting rapid series of US pulses
  - Echoes from stationary tissues are same from pulse to pulse
  - Echoes from moving scatters exhibit slight differences in time for signal to be returned to receiver
  - These differences in US signal are processed to produce Doppler sonogram
- Doppler spectrum: Time vs. velocity waveform that represents variation in intravascular blood flow velocities measured using Doppler shift
- Spectral Doppler imaging: Utilizing US waves to display blood flow velocity over time as waveform
- Doppler effect: Perceived frequency change of sound based on movement of source of sound relative to receiver
  - Frequency perceived by receiver will be higher if source moving toward receiver and lower if source is moving away from receiver
- Doppler shift: Difference between transmitting and reflected frequency emitted from transducer
  - Defined as ΔF = 2F₀V cos Ø/c
    - ΔF is Doppler shift
    - F₀ is transmit frequency
    - V is velocity of reflector
    - Ø is angle of incidence between US beam and direction of blood flow
    - c is speed of sound in tissue
- 2 types of imaging can be used for Doppler shifts measurement
  - CWD
    - Simplest and oldest Doppler imaging technique
    - Uses transducer with separate receiver and transmitter so signal can be transmitted and received continuously
    - High sensitivity and not susceptible to aliasing
    - Most important drawbacks are absence of corresponding B-mode image and lack of depth resolution, making it impossible to accurately localize source of Doppler signal
  - PWD
    - Uses transducers that can transmit US pulses and measure Doppler shift sequentially within operator-defined region of interest
    - Using time-of-flight from transmission to reception of US signal, PWD can determine position from which reflected Doppler signal was produced
    - US Doppler shifts are displayed in spectral form, with frequency shifts on vertical axis and time on horizontal axis, demonstrating blood velocity as function of time
- Pulse repetition frequency: Number of pulses of US occurring in 1 second
  - Nyquist limit = to 1/2 of pulse repetition frequency
    - Aliasing will occur when velocity exceeds Nyquist limit
- Resistive index (RI) calculated from spectral measurements and defined as: RI = (PSV - EDV)/PSV
  - Commonly used for presenting resistance of peripheral artery
- Pulsatility index (PI) calculated from spectral measurements and defined as: PI = (PSV - EDV)/MV
  - Used for demonstrating differences in arterial flow resistance

IMAGING ANATOMY

General Anatomic Considerations

CLINICAL IMPLICATIONS

Clinical Importance
Clinical Applications
Limitations
Diagnostic Checklist

Selected References

Nuffer Z et al: Spectral Doppler ultrasound of peripheral arteries: a pictorial review. Clin Imaging. 46:91-97, 2017
Kruskal JB et al: Optimizing Doppler and color flow US: application to hepatic sonography. Radiographics. 24(3):657-75, 2004
Taylor KJ et al: Doppler US. Part I. Basic principles, instrumentation, and pitfalls. Radiology. 174(2):297-307, 1990
Burns PN: The physical principles of Doppler and spectral analysis. J Clin Ultrasound. 15(9):567-90, 1987

Related Anatomy

Related Differential Diagnoses

References

Tables

KEY FACTS

Terminology
Basic Imaging Considerations
Physiology

TERMINOLOGY

Abbreviations
- Continuous-wave Doppler (CWD)
- Pulsed-wave Doppler (PWD)
- Peak systolic velocity (PSV)
- End diastolic velocity (EDV)
- Mean velocity (MV)
Synonyms
- Spectral Doppler imaging
- Range-gated Doppler
Definitions
- US images of spectral Doppler flow are obtained from measurements of movement by transmitting rapid series of US pulses
  - Echoes from stationary tissues are same from pulse to pulse
  - Echoes from moving scatters exhibit slight differences in time for signal to be returned to receiver
  - These differences in US signal are processed to produce Doppler sonogram
- Doppler spectrum: Time vs. velocity waveform that represents variation in intravascular blood flow velocities measured using Doppler shift
- Spectral Doppler imaging: Utilizing US waves to display blood flow velocity over time as waveform
- Doppler effect: Perceived frequency change of sound based on movement of source of sound relative to receiver
  - Frequency perceived by receiver will be higher if source moving toward receiver and lower if source is moving away from receiver
- Doppler shift: Difference between transmitting and reflected frequency emitted from transducer
  - Defined as ΔF = 2F₀V cos Ø/c
    - ΔF is Doppler shift
    - F₀ is transmit frequency
    - V is velocity of reflector
    - Ø is angle of incidence between US beam and direction of blood flow
    - c is speed of sound in tissue
- 2 types of imaging can be used for Doppler shifts measurement
  - CWD
    - Simplest and oldest Doppler imaging technique
    - Uses transducer with separate receiver and transmitter so signal can be transmitted and received continuously
    - High sensitivity and not susceptible to aliasing
    - Most important drawbacks are absence of corresponding B-mode image and lack of depth resolution, making it impossible to accurately localize source of Doppler signal
  - PWD
    - Uses transducers that can transmit US pulses and measure Doppler shift sequentially within operator-defined region of interest
    - Using time-of-flight from transmission to reception of US signal, PWD can determine position from which reflected Doppler signal was produced
    - US Doppler shifts are displayed in spectral form, with frequency shifts on vertical axis and time on horizontal axis, demonstrating blood velocity as function of time
- Pulse repetition frequency: Number of pulses of US occurring in 1 second
  - Nyquist limit = to 1/2 of pulse repetition frequency
    - Aliasing will occur when velocity exceeds Nyquist limit
- Resistive index (RI) calculated from spectral measurements and defined as: RI = (PSV - EDV)/PSV
  - Commonly used for presenting resistance of peripheral artery
- Pulsatility index (PI) calculated from spectral measurements and defined as: PI = (PSV - EDV)/MV
  - Used for demonstrating differences in arterial flow resistance

IMAGING ANATOMY

General Anatomic Considerations

CLINICAL IMPLICATIONS

Clinical Importance
Clinical Applications
Limitations
Diagnostic Checklist

Selected References

Nuffer Z et al: Spectral Doppler ultrasound of peripheral arteries: a pictorial review. Clin Imaging. 46:91-97, 2017
Kruskal JB et al: Optimizing Doppler and color flow US: application to hepatic sonography. Radiographics. 24(3):657-75, 2004
Taylor KJ et al: Doppler US. Part I. Basic principles, instrumentation, and pitfalls. Radiology. 174(2):297-307, 1990
Burns PN: The physical principles of Doppler and spectral analysis. J Clin Ultrasound. 15(9):567-90, 1987

KEY FACTS

Terminology

Basic Imaging Considerations

Physiology

TERMINOLOGY

Abbreviations

Synonyms

Definitions

IMAGING ANATOMY

General Anatomic Considerations

CLINICAL IMPLICATIONS

Clinical Importance

Clinical Applications

Limitations

Diagnostic Checklist

Selected References

Tables

KEY FACTS

Terminology

Basic Imaging Considerations

Physiology

TERMINOLOGY

Abbreviations

Synonyms

Definitions

IMAGING ANATOMY

General Anatomic Considerations

CLINICAL IMPLICATIONS

Clinical Importance

Clinical Applications

Limitations

Diagnostic Checklist

Selected References