High resolution Thermal Strain Imaging (TSI) using an ultrasound (US) microscope was applied to excised porcine tissues. Samples were placed in a temperature controlled water chamber and scanned transversely and longitudinally using a custom high resolution microscope. Phase-sensitive, correlation-based speckle tracking was applied to map the spatial distribution of temporal strain across the sample. TSI differentiated fatty tissue from the water-based arterial wall and muscle with high contrast and a spatial resolution of 60 microns for a 50 MHz transducer. Both transverse and longitudinal TSI images compare well with the B-Scan of arterial wall structures, including intima, media, adventitia and overlying fatty tissue. These in-vitro results demonstrate the feasibility of high resolution TSI with a small temperature change (less than a 1°C) for plaque characterization.