Colour Doppler Flashcards
Unlike spectral Doppler
Colour offers a wonderful survey tool to quickly assess large regions of the patient
Blessings of colour
- Quick survey of large area of patient
- Detection of disease
- Blood flow detection in malignant/benign tumors can demonstrated
- Provides spatial dimension over large area
Curse of colour
Yields only an estimate of the mean velocity
Does not give full spectrum information
Can appear normal visually while spectral depicts presence of disease
Must be used with spectral Doppler to interpret disease in vascular studies
Does not provide peak velocities, velocity gradients or spectral broadening
Colour Doppler
Colour Doppler allows flow information over a large spatial areas
Scanned modality
Provides lateral dimension
In colour, after the transmit pulse, it listens with a series of range gates which spans the entire time until the next transmit pulse
Colour, received pixel-by-pixel information to determine the spatial data for the depth
Spectral Doppler
Spectral Doppler provides information along a specific line or with a specified gate range
Non-scanned modality
Does not provide lateral dimension
In Spectral, after the transmit pulse, it listens to only the specified rage gate at a specific depth
How is colour Doppler preformed
Color Doppler utilizes Doppler techniques to provide flow information over a scanned region of the patient.
Unlike PW and CW Doppler, color Doppler does not provide spectral information.
Color Doppler provides an estimate of the mean velocity.
what is created by repeatedly scanning a single line in the same direction
Colour packet
the packet is then
Scaned across the body to produce a frame
how is colour similar to 2D
packets of acoustic lines are scanned across the body
how is colour similar to spectral
A single line is transmitted repatedly in the same directin
Creating the colour scan step one
TTransmit pulse in a single line
creating the colour scan step two
Repeats this 4-12 times in the same line (colour packet)
creating the colour scan step three
Doppler information from the scan line is obtained by a series of range gates within each acoustic line of the packet
creating the colour scan step 4
Correlation is then made using each of the lines within the packet to yield an estimated mean velocity at each range gate along the line
creating the colour scan step 5
The direction of the line is then changed and a new packet is then transmitted in the new direction
creating the colour scan step 6
This process repeats until information is acquired from the scan region of interest
why is a packet of lines transmitted
So that an average velocity can be determined at each depth along the line
Colour has _______temporal resolution
Poor temporal reoslution
why does colour have a poor temporal resolution
Since every colour line displayed on the screen represents an entire packet of acoustic lines, creating an entire colour scan requires many more acoustic lines than creating an entire conventional 2D scan
A higher frame time
Causes lower frame frequency
A lower frame rate implies a greater likelihood of not capturing a short duration event
Creating the colour scan step 7
Once the packet has been transmitted and correlation performed the data is filtered and colours assigned on a pixel-by-pixel basis based on a colour scale/bar. The colour bar is a key which relates mean frequency shifts detected with a colour
creating the colour scan step 8
Once the system determines the Doppler shift as it is assigned a colour based on the colour bar/scale (colour map)
Colour bar has
negative(-) and positive(+) direction
Positive-towards
Negative-away
Negative implies what
Negative frequency shift and the insonifcation angle is greater than 90