Loops can form when point defects coalesce. Well known are TEM studies of radiation damage and the formation of dislocation loops. By diffraction contrast imaging you can quantify the strain fields of point defect clusters.

(compare for instance David B. Williams and C. Barry Carter; Transmission Electron Mictroscopy, Chapter 26, Imaging Strain fields)

In HRTEM or HRSTEM you see no single point defects. You see a row of atoms and have to do contrast simulations by EMS, Mac Tempas …. But I think this is no promising task.

Significantly are the lattice parameter and the diffuse scattering.

Compare for instance:

Kim, C., Feng, R., Conrad, E.H., Miceli, P.F.:Nanoclustering of vacancies in thin metal films revealed by x-ray diffuse scattering;Applied Physics Letters; Volume 91, Issue 9, 2007, Article number 093131

Valikova, I.V. , Nazarov, A.V.: Simulation of pressure effects on self-diffusion in BCC metals, Defect and Diffusion Forum, Volume 277, 2008, Pages 125-132