The heart is the key here. Notice the low density appearance within the myocardium, or more specifically, in the subendocardial region of the left ventricle.

Answer: Subendocardial fat deposition consistent with prior myocardial infarct (ie fatty replacement of post-infarct scarring)

Reference: http://www.ajronline.org/doi/full/10.2214/AJR.08.1608 or http://pubs.rsna.org/doi/full/10.1148/rg.306105519