As in the responses to that question, we need to know what software produced the file, or we need documentation on the file format. The suffix '.img' is used by multiple vendors for different formats. There is no standard .img format.
This is not a widely used image format. At least not widely used by enough people who use MATLAB so imread() will not read it. And I suppose people could come up with their own .img format. So you need to find out the format and check theFile Exchange in the hopes someone has made a reader for it. Or else write your own.
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