MetaVi Labs has developed algorithms that remove motion jitter induced by stage re-position errors.

For example, in this un-stabilized time-lapse movie, we see cancer cells and T cells. The T cells move at a much higher speed than the cancer cells. But with all the cell movement, you may not notice that the entire image is moving from frame to frame. If you focus your attention on the cells indicated in the center you will notice an Y-axis jitter. This is very pronounced in the first three seconds of the movie.

If this were uncorrected, it would introduce additional motion into the cell tracks. When measuring cell speeds this jitter in the tracks would add additional speed which is not actually present. So its important to correct this motion jitter introduced by the X Y stage. When time-lapse scanning a multi-well plate, at each time point, the X Y stage must return to the original position in each well. But all stages introduce some re-position error, some more than others, because of the precision limits of the stage motors.

So we developed a specialized technique to fix this problem. The first step is to find the cells which move the least and also move in unison. While each cell is doing its own thing, stage positioning errors affect all cells equally. So the trick is to remove the change in position due to individual cells but find the X Y shift that is common to all the cells. This takes a massive amount of calculations on a large images (the original images from the microscope were 2048 x 2048). The goal is to correct the error down to sub-pixel resolution. Sub-pixel correction is achieved by estimating pixel values between pixels.

As you can see in the corrected movie below, there is no longer and stage error shift. The only motion is due to the cells moving individually.

Thursday, February 14, 2019 By David Drell