HI Thank for asking to HCM In MRI heterogeneous intensity of signal is very common encounter, it means that the diversity is there, and the nature of signals are also different, this indicate so many pathologies of musculoskeletal system to some time soft tissues, and that need to be correlated with clinical history of patient, as you have given history of backache so the chances of lumber spondylosis is more likely if you do not have neurological deficit, if you have neurological problem then the interpritation would be in that sense only, have nice day.