Abstract: A method of characterizing a sample comprising a thrombus collected from a patient is described. The method comprises illuminating the sample with electromagnetic light, detecting light reflected or Raman scattered by the sample at a plurality of wavelengths, and classifying the sample based on a spectral analysis of the detected reflected or Raman scattered light. The spectral analysis may comprise principal component analysis PCA, discriminant function analysis DFA, or cluster analysis. The classification may be according to thrombus color, i.e., erythrocyte rich “red” versus erythrocyte poor “white”, or according to degree of a clinical marker, e.g., microvascular obstruction MVO.