## CASA terminology

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.