## Time gated Phasor

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...

### Time Gated Phasor FAQ

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 estimation.
•    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 for segmentation.

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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