Phasor approach is powerful technique for visualization and analysis of lifetime
images. Here we show the application of this approach to different gate settings
(number of time gates, total measurement window...
What is the Phasor approach?
• The phasor approach is used to transform the decay curves
into a 2D plot using the Fourier transformation. All the decays with single exponential
behavior fall on a semicircle. Multi-exponential decays fall inside the semicircle.
What is this method for?
• This is a method for analysis of lifetime images;extracting
the lifetimes and unmixing the pure components.
What can it do?
• It can visualize the lifetime images on a 2D plot called phasor
plot based on their lifetimes.
• It can be used for unmixing of two components and it can
extract the lifetimes of each individual components in a blind way.
• It provides a solution for pixel by pixel average lifetime
• It is fast, and instrument response effect is taken into
account by using a reference measurement from a dye with known lifetime.
• Segmentation of unlimited number of components can be performed
by making region of interest on the phasor plot and transforming the phasor points
back to the original image.
What can't it do?
• It can not resolve the lifetimes for a multi-exponential
decays and it only provide average lifetime.
What is the reciprocal transformation?
• Since the decay curves are mapped on a unique location
on the phasor plot based on their lifetimes, there is a one to one correlation between
the decays and their position on the phasor plot. Therefore a reciprocal transformation
can be performed by making a region of interest on the phasor plot which show similar
behavior and transforming back to the image. This provides a very simple method
What is the global analysis?
• In phasor approach global analysis is usually referred
to unmixing of two components and extracting their lifetimes. In this method it
is assumed that the lifetimes of two components are invariant in whole image and
only their fractional intensities vary from pixel to pixel.Assuming that there is
a variety of fractional intensities in the image, the phasor of all pixels fall
on a line in phasor plot where the intersection of this line with reference semicircle
determines the lifetimes of two components.
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