@xDiavalx this approach is ok for small volumes but it does not scale well. Viguera et al. [1] have shown the feasibility of GPU splatting (which your technique boils down to) for sparse volumes (in their vascular volumes, only around 2% of the voxels contribute to the rendering), but for volumes in the medical context which I myself as well as the OP are interested in, volume sizes of 512^3 are not uncommon with at least 50% of voxels contributing. This would require UE to handle about 65 Million (static) particles… I wonder if anyone has tried how far you can go in terms of resolution/number of particles on a 2016 graphics card and UE4, maybe @dokipen has some insights here since he seems to have tried it?
[1] http://www.vis.uni-stuttgart.de/plain/vdl/vdl_upload/148_7_vega-et-al-VIS2006.pdf