An automated method of quantifying particle velocity from linescans is very useful for analyzing capillary-level blood flow data obtained with two-photon microscopy.  The Radon transform method is an fast and robust method for obtaining velocity information from linescan data. 

This demo code generates pseudo-data, and then uses the Radon transform to calculate the angle of the streaks in a user-defined time window. When the spatial dimension of the space-time plot is along the x axis, and the time dimension is along the y-axis, the cotangent of the angle of the streaks is proportional to the velocity. The error as a fraction of the velocity will be largest for near horizontal and vertical lines. For angles of less than 10 degrees from horizontal, a cross-correlation method is more appropriate.

The publication describing the method is:

• Drew PJ, Blinder P, Cauwenberghs G, Shih AY, Kleinfeld D, Rapid determination of particle velocity from space-time line-scan data using the Radon transform, Journal of Computational Neuroscience, 29(1-2):5-11

  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4962871/

 

 

See also:

• Chhatbar PY, Kara P. Improved blood velocity measurements with a hybrid image filtering and iterative Radon transform algorithm. Frontiers in Neuroscience. 2013;7:106. doi:10.3389/fnins.2013.00106.