Simple Validation of non-Flow

In the early phase of HRF my predecessor at the hostpital and me validated the SLDF method with quite simple experiments.

With one of the first (and easiest) experiments we also tried to find the acceptable range of DC, which is the intensity of an image.

I did an examination of a drawing paper, mounted in front of the HRF camera. In the DC image below you can also see the grid.

Figure 1: DC image of a drawing paper SLDF image

As we expected, the resulting Flow image below shows no Flow (figure 2, histogram in figure 3)

Figure 2: Flow and averaged Flow image of a drawing paper SLDF image

Figure 3:Histogram of averaged Flow image of a drawing paper SLDF image

This is a simple proof that the method works properly for areas with no moving particles. But it is getting even more interesting if we look at a scatterplot of DC-Flow values. This plot shows that the Flow values do not depend on the DC values as we expect - except for DC values above 225[AU]. These Flow values are plotted as blue points.

The overexposure leads to wrong Flow values, not correlated to DC anymore. The same effect we also observe for underexposed pixels and images. That's why these DC values are excluded from all calculations. The valid DC range can be adjusted using the settings dialog. But be aware: If you extend the range you will get wrong perfusion parameters and the vessel detection algorithms will produce wrong results.

Figure 4 DC-Flow scatter plot for a drawing paper SLDF image