A system and method are disclosed that facilitate characterizing vascular plaque tissue based upon spectral analysis of intravascular ultrasound echo signal segments. In particular, split spectrum analysis of an integrated backscatter parameter introduces a spectral resolution component to parameterization of received intravascular ultrasound echo signal segments. The resulting parameter values for each of multiple bands within a larger frequency band supported by an ultrasound system are applied to plaque tissue characterization criteria to render a plaque tissue characterization corresponding to the corresponding ultrasound echo signal segments.