A biopsy is predicated on the idea that you can identify good from bad. You might not be able to identify the origin cell but you would be able to pick out metastasization.
You certainly can take pictures. And not to be too reductive: cells are visible in a light microscope. The point is that the scale that cells are at is not really at the quantum level. People have been interacting with individual cells for decades: https://www.youtube.com/watch?v=GTiKFCkPaUE
I also have a degree in physics but in addition I have a degree in computer science. 36 Trillion is not a very large number for modern computers anymore. I am sure even today we could build machines that would filter the cells in your blood by images and do it at 10s of millions per second.
You certainly can take pictures. And not to be too reductive: cells are visible in a light microscope. The point is that the scale that cells are at is not really at the quantum level. People have been interacting with individual cells for decades: https://www.youtube.com/watch?v=GTiKFCkPaUE
I also have a degree in physics but in addition I have a degree in computer science. 36 Trillion is not a very large number for modern computers anymore. I am sure even today we could build machines that would filter the cells in your blood by images and do it at 10s of millions per second.