Power Doppler and Artifcats

• Does not show direction of flow
• also known as color power/energy mode
• the strength of teh reflected signal is processed
• strength is also known as amplitude
• The signal is processed without regard to the blood's direction or speed
• The brightness is directly related to the number of moving blood cells

As in color Doppler, changing the transmit Doppler frequency in PDI can have a dramatic effect on the receiced signal

• Improved sensitivity to low flow or slow velocity
• Unaffected by Doppler angles
• No aliasing since velocity info is ignored

• Very slow frame rate
• Lower temporal resolutions (susceptible to motion of transducer, patient or soft tissue, flash artifact)
• No flow direction
• No velocity measurement

• Doppler sampling rate is too low in comparison to measured blood velocity
• Aliasing occurs when the doppler shift frequency exceeds haf the PRF
• This is called the Nyquist Limit

• Lower transmit frequency
• Adjust scale to its maximum (adjusting teh scale will adjust the PRF)
• Select a lower frequency transducer (doppler shift directly related to transmit frequency)
• Repostion the transducer so teh area of interest is shallower (this increases the PRF)
• Adjust the baseline

• Duplicates a structure on the other side of a strong reflector
• Common around the diaphragm and the pleura because of the total reflection from the air-filled lung

• Occurs in color doppler
• Anything within the field of view that moves relative to the transducer is shown in color (generate blotches of color that can obscure a large portion of the field of view)
• Correct by (increasing wall filter, decreasing persistence, reducing the width of the color box

• It is the extension of color beyond the region of flow ot the adjacent tissue
• Eliminate color bleed by decreasing the color gain or transmit power

• Random variation in signal detection causes area w/o flow to be encoded with color
• Increase filter or threshold to eliminate he low level echoes

• Useful flow phenomenon
• A mixture of color is seen withing the soft tissue adjacent to the blood vessel as a result of the vessel wall vibration (it is a valuable marker of vascular pathology, teh wall vibration is an indication of a severe flow disturbance)
• Can be seen in AV fistulae, arterial stenosis, and pseudoaneurysms

• A small strong signal prominent above and below the baseline
• Occurs in systole