Plaque imaging with CT coronary angiography:Effect of intra-vascular attenuation on plaque type classification

AIM:To assess the attenuation of non-calcified atherosclerotic coronary artery plaques with computed tomography coronary angiography(CTCA).METHODS:Four hundred consecutive patients underwent CTCA(Group 1:200 patients,Sensation 64 Cardiac,Siemens;Group 2:200 patients,VCT GE Healthcare,with either Iomeprol 400 or Iodixanol 320,respectively) for suspected coronary artery disease(CAD).CTCA was performed using standard protocols.Image quality(score 0-3),plaque(within the accessible non-calcified component of each non-calcified/mixed plaque) and coronary lumen attenuation were measured.Data were compared on a per-segment/perplaque basis.Plaques were classified as fibrous vs lipid rich based on different attenuation thresholds.A P < 0.05 was considered significant.RESULTS:In 468 atherosclerotic plaques in Group 1 and 644 in Group 2,average image quality was 2.96 ± 0.19 in Group 1 and 2.93 ± 0.25 in Group 2(P ≥ 0.05).Coronary lumen attenuation was 367 ± 85 Hounsfield units(HU) in Group 1 and 327 ± 73 HU in Group 2(P < 0.05);non-calcified plaque attenuation was 48 ± 23 HU in Group 1 and 39 ± 21 HU in Group 2(P < 0.05).Overall signal to noise ratio was 15.6 ± 4.7 in Group 1 and 21.2 ± 7.7 in Group 2(P < 0.01).CONCLUSION:Higher intra-vascular attenuation modifies significantly the attenuation of non-calcified coronary plaques.This results in a more difficult characterization between lipid rich vs fibrous type.