Read back limited data from compute shader?

Hi,

Im trying to build a particle filter on Compute Shaders.

Im using this example as a basis: http://florian-noirbent.com/blog/en/dx11-particle-engine/

The basic implementation is working, but I need to read back results from the GPU. I can download all particles but that is highly inefficient as I only need a small subpart of the data.

How would I go about reading back only a part of the ComputeBuffer?

Do I create a newer small buffer and let it read the results or is there a way to fetch a part only?

If the first, how do I figure out what indices to read from?

Kind regards.

Jesper