The proprietary semen analysis system of Biophos is based on a fundamentally new technology rendering very accurate and reproducible results clearly outperforming the current computerized semen analysis systems on the market.
The QualiSperm™ image recognition is based on a very advanced image recognition algorithm where we use Digital Sperm Washing (DSW) to improve discrimination between sperms and other objects in the image.
Additionally, the assessment of highly concentrated sperm samples rely on a newly developed method called image correlation analysis (IMA). Determination of sperm motility is partly based on trajectory analysis and partly on image correlation analysis.
The advantage of this combination is that both methods are complementary: trajectory analysis is very accurate when sperm concentration is low and leads to very precise determination of sperm velocity at low concentrations, whereas image correlation is far superior at high concentrations where trajectory analysis fails.
At low to medium concentrations sperm motility is determined using trajectory analysis. The basic principle of trajectory analysis is relying on the acquisition of sequential images. In each image the relative positions of all detected sperms are determined and compared with the relative positions of the detected sperms in the previously acquired image. In this way the trajectory of all detected sperms can be calculated. The time it takes the sperm to travel from A to B (the trajectory) can easily be evaluated. Thus the exact speed of each sperm can be calculated.
Image correlation analysis
At high concentrations a novel method called image correlation is utilized. The idea behind image correlation stems from an already well-established spectroscopic method called fluorescence correlation spectroscopy (FCS).
In FCS the concentration and the diffusion time (which is related to the molecular weight) of a fluorescently labeled molecule is determined by a confocal fluorescence microscope. The underlying principle is related to the fact that random diffusion of fluorescently labeled molecules excited by a focused laser beam gives rise to specific intensity fluctuation signature which can be used to determine the concentration and the size of the molecule.
In image correlation a conventional phase contrast microscope is used to acquire sequential images of moving sperms. In contrast to FCS where a diffraction limited laser spot is used for excitation, image correlation uses the projected image of sperms on pixel volumes given by the microscope which is equipped with a digital camera. Every pixel of an image is correlated with the same pixel of the following image.
This allows the exact determination of concentration and the motility. The real advantage of using image correlation is when sperm concentrations is high. At this concentration trajectory analysis fails to measure sperm motility accurately since it is very difficult/impossible to determine which Our method allows to measure high concentrations of more than 1000 sperms per analysis.
Our system analyzes per one measurement over 1000 sperms within 6 seconds. You can measure up to nine different arrays (up to 10,000 sperms). The accuracy and speed of the sperm quality analyzer is unmatched by any CASA system or by manual methods.
Method: Projection of individual sperms on a pixel grid of boxes
Definition of pixel boxes and pixel volumes
Analysis of number of pixel intensity fluctuations instead of trajectories
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