How can I measure the length of my tissue in an image sequence automatically with ImageJ?

I have multiple sequences of images from my micropipette aspiration experiments that look somewhat comparable to this: https://www.youtube.com/watch?v=HpY_2_e7b6Y

Now I would like to track the length of the tissue within the pipette automatically for all the different images in the sequence.

Does anyone know how this can be done?

Thanks!

Solution

You could probably do it with a macro: first, you manually draw a line in the middle of the channel to define the direction. Then, for each image of the movie, you try to find the edge of the pipette and the interface. To do that, you can try to use the "Process>Find Edges" function. Depending on the quality of your images, you might need several steps. Finally, you just need to find the distance between these two points.

Here is a quick-and-dirty macro which kind of gives a not-too-wrong result with the Youtube video:

print("\\Clear");
run("Clear Results");

run("Duplicate...", "title=Stack-1 duplicate range=1-5");

selectWindow("Stack-1");
run("Find Edges", "stack");

waitForUser("Please draw a line and click OK.");
//makeLine(402, 238, 170, 221);

setLineWidth(20);

//for each frame of the movie
for(s=1;s<=nSlices;s++){
    setSlice(s);

    profile=getProfile();
    maxProfile=Array.findMaxima(profile,15);
    diff=abs(maxProfile[1]-maxProfile[0]);
    print("max at: "+maxProfile[1] +" "+ maxProfile[0]);

    print("Slice "+s+" the difference is: "+diff+" px");
    setResult("Time",nResults,s*2);
    setResult("Position",nResults-1,diff/200);
}

I tested it on five frames from the Youtube video (available here for about 1 month, 6MB): it gives almost consistent results, but it's very approximative and could be easily improved. I think the main idea is correct.