Studies done on carotid arteries suggest that the morphology and composition of atherosclerotic plaque are predictive of stroke risk. The goal of this investigation has been to demonstrate that the true acoustic integrated backscatter (IBS) from plaque regions can be measured non-invasively, based on which plaque composition may be inferred and thus become a tool to estimate the likelihood of a lesion or plaque being stable or vulnerable, i.e. having a risk of causing a stroke.To obtain the true IBS non-invasively, the scattering and aberrating effect of the intervening tissue layers must be overcome. This is achieved by using the IBS from arterial blood as a reference backscatter, specifically the backscatter from a blood volume along the same scan line as and adjacent to the region of interest. We have shown that the variance of the IBS estimate of the blood backscatter signal can be quantified and reduced to a specified tolerable level.