This article describes some standard terminology for variables measured by CASA systems. In addition to the parameters you can obtain in the SpermCell ™ report, you can find the parameters found in the reports from CASA systems.
1. VCL, curvilinear velocity (µm/s). Time-averaged velocity of a sperm head along its actual curvilinear path, as perceived in two dimensions in the microscope. A measure of cell vigour.
2. VSL, straight-line (rectilinear) velocity (µm/s). Time-averaged velocity of a sperm head along the straight line between its first detected position and its last.
3. VAP, average path velocity (µm/s). Time-averaged velocity of a sperm head along its average path. This path is computed by smoothing the curvilinear tra- jectory according to algorithms in the CASA instrument; these algorithms vary between instruments, so values may not be comparable among systems.
4. ALH, amplitude ofl ateral head displacement(µm). Magnitude of lateral displacement of a sperm head about its average path. It can be expressed as a maximum or an average of such displacements. Different CASA instruments compute ALH using different algorithms, so values may not be comparable among systems.
5. LIN, linearity. The linearity of a curvilinear path,VSL/VCL.
6. WOB, wobble. A measure of oscillation of the actual path about the average path, VAP/VCL.
7. STR, straightness. Linearity of the average path, VSL/VAP.
8. BCF, beat cross frequency(Hz).The average rate at which the curvilinear path crosses the average path.
9. MAD, mean angular displacement (degrees).The time averaged absolute values of the instantaneous turning angle of the sperm head along its curvilinear trajectory.
Note: Different CASA instruments use different mathematical algorithms to compute many of these movement variables. The comparability of measurements across all instruments is not yet known.
*This entire article is taken from the WHO Laboratory Handbook-Examination and processing of human semen, from pages 138 and 139 of the 5th Edition. To the complete of the book and references to the information given http://apps.who.int/iris/bitstream/10665/44261/1/9789241547789_eng.pdf?ua=1
**Images used in this article are taken from http://newshawktime.com web site.