You can use it but you need to use a filter to get better result and must your sample be very clean and without any contaminants.
The best choice is ADAM-MC, an automated cell counter, performs viability and cell counting measurements using the PI staining method of dead-cell staining combined with advanced image analysis.
Why must my sample be very clean of contaminants? I assume you mean red blood cells and the like? Isn't the TC20 able to distinguish between different cell populations?