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KEY FACTS
Terminology
Power Doppler Imaging Principles
Basic Imaging Considerations
TERMINOLOGY
Abbreviations
- Power Doppler imaging (PDI)
- Power color Doppler imaging (PCDI)
Synonyms
- Color Doppler energy imaging
- Ultrasound power angiography
Definitions
- Doppler effect: Frequency change from transmitting and reflected sound waves based on source relative to receiver
- Positive frequency shift: When reflector is moving toward ultrasound beam
- Negative frequency shift: When reflector is moving away from ultrasound beam
- 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 blood flow
- Ø is angle of incidence between US beam and direction of blood flow
- c is speed of sound in tissue
- Note that Doppler shift is highly dependent on angle of incidence and can be maximized with Ø = 0⁰ or minimized with = 90⁰
- Defined as ΔF = 2F₀V cos Ø/c
- PDI: 1 of 3 commonly used Doppler techniques
- Measured by strength of Doppler signal
- Unlike color Doppler imaging (CDI), PDI is independent of velocity and direction of blood flow
- Since there is no velocity or direction, aliasing is eliminated
- Less dependent on angle of insonation than CDI
- Amplitude: Strength of returning signal is dependent on density of red blood cells, sample volume, attenuation of surrounding tissue, and blood vessel in relation to sample volume size
- Greater density of red blood cells within sample volume results in greater amplitude
- Rouleaux effect: Cluster of red blood cells within blood vessel
- Increased thickness (density) or cluster of red blood cells results in more reflective power Doppler signal
- This effect is visualized mostly in central, larger vessels due to plug flow
- Plug flow has less turbulence to disrupt clumping of red blood cell or Rouleaux flow
- Depth: With increasing depth and attenuation, return of ultrasound signal is weaker
- Important to use appropriate depth to optimize PDI
- Doppler effect: Frequency change from transmitting and reflected sound waves based on source relative to receiver
IMAGING ANATOMY
Anatomic Considerations
Technical Considerations
CLINICAL IMPLICATIONS
Diagnostic Checklist
Selected References
- Evans DH: Colour flow and motion imaging. Proc Inst Mech Eng H. 224(2):241-53, 2010
- Rubens DJ et al: Doppler artifacts and pitfalls. Radiol Clin North Am. 44(6):805-35, 2006
- Evans DH et al: Doppler Ultrasound: Physics, Instrumentation and Signal Processing, 2nd Ed. Wiley Publishing, 2000
- Allan PL et al: Clinical Doppler Ultrasound Philadelphia: Churchill Livingstone, 2000
- Kremkau FW: Doppler principles. Semin Roentgenol. 27(1):6-16, 1992
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References
Tables
Tables
KEY FACTS
Terminology
Power Doppler Imaging Principles
Basic Imaging Considerations
TERMINOLOGY
Abbreviations
- Power Doppler imaging (PDI)
- Power color Doppler imaging (PCDI)
Synonyms
- Color Doppler energy imaging
- Ultrasound power angiography
Definitions
- Doppler effect: Frequency change from transmitting and reflected sound waves based on source relative to receiver
- Positive frequency shift: When reflector is moving toward ultrasound beam
- Negative frequency shift: When reflector is moving away from ultrasound beam
- 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 blood flow
- Ø is angle of incidence between US beam and direction of blood flow
- c is speed of sound in tissue
- Note that Doppler shift is highly dependent on angle of incidence and can be maximized with Ø = 0⁰ or minimized with = 90⁰
- Defined as ΔF = 2F₀V cos Ø/c
- PDI: 1 of 3 commonly used Doppler techniques
- Measured by strength of Doppler signal
- Unlike color Doppler imaging (CDI), PDI is independent of velocity and direction of blood flow
- Since there is no velocity or direction, aliasing is eliminated
- Less dependent on angle of insonation than CDI
- Amplitude: Strength of returning signal is dependent on density of red blood cells, sample volume, attenuation of surrounding tissue, and blood vessel in relation to sample volume size
- Greater density of red blood cells within sample volume results in greater amplitude
- Rouleaux effect: Cluster of red blood cells within blood vessel
- Increased thickness (density) or cluster of red blood cells results in more reflective power Doppler signal
- This effect is visualized mostly in central, larger vessels due to plug flow
- Plug flow has less turbulence to disrupt clumping of red blood cell or Rouleaux flow
- Depth: With increasing depth and attenuation, return of ultrasound signal is weaker
- Important to use appropriate depth to optimize PDI
- Doppler effect: Frequency change from transmitting and reflected sound waves based on source relative to receiver
IMAGING ANATOMY
Anatomic Considerations
Technical Considerations
CLINICAL IMPLICATIONS
Diagnostic Checklist
Selected References
- Evans DH: Colour flow and motion imaging. Proc Inst Mech Eng H. 224(2):241-53, 2010
- Rubens DJ et al: Doppler artifacts and pitfalls. Radiol Clin North Am. 44(6):805-35, 2006
- Evans DH et al: Doppler Ultrasound: Physics, Instrumentation and Signal Processing, 2nd Ed. Wiley Publishing, 2000
- Allan PL et al: Clinical Doppler Ultrasound Philadelphia: Churchill Livingstone, 2000
- Kremkau FW: Doppler principles. Semin Roentgenol. 27(1):6-16, 1992
