Lastly, we proceeded to investigate age related changes in plaque lipid microenvironment in 23mo mice as compared to the 18mo old. To our surprise, only small changes were observed between 18mo and 23mo animals. To do so, we compared the ratio of core/periphery signal across the ages. Here, we observed changes in phosphatidylinositols. In particular, while the previously reported (a) lyso-phosphatidylinositol, LPI (18:0) (Figure ,B), did not display any age-related changes, the larger (c) arachidonic acid conjugated PI (38:4) showed a trend towards a (d) decrease in the core/periphery signal ratio with age (although non-significant). This pattern was even more prominent for a previously unreported, (e) docosahexaenoic acid PI (18:0/22:6); with a significantly (f) higher core/periphery signal in the 18mo as compared to 23mo mice.