Objective To study the clinical value of 16-slice spiral CT combined with MMP-9 and TIMP-1 in assessing carotid atherosclerosis in elderly cerebral infarction(CI) patients.Methods One hundred and eighty-six CI patients served as group A and 190 asymptomatic carotid atherosclerosis patients served as group B with 90 healthy subjects served as a control group in this study.The patients in group A were further divided into unstable plaque(A-1) group,stable plaque(A-2) group and plaque-free(A-3) group while those in group B were further divided into unstable plaque(B-1) group,stable plaque(B-2) group and plaque-free(B-3) group.The patients included in this study underwent multislice spiral CT angiography(MSCTA) and Doppler ultrasonography.Their serum levels of MMP-9 and TIMP-1 were measured.Their carotid artery steno sis and plaques were detected.The efficacy of MMP-9 and TIMP-1 in diagnosis of unstable plaques in CI patients was analyzed.Results The rate of mild stenosis detected by MSCTA was significantly lower while that of severe stenosis detected by MSCTA was significantly higher in group A than in group B(23.1％ vs 48.9％,P=0.000;48.4％ vs 16.8％,P=0.000).The rate of unstable plaques detected by MSCTA and ultrasonography was 81.7％ and 83.2％ respectively in groups A and B.The rate of stable and unstable plaques detected by MSCTA was significantly higher in group A than that detected by CT in group B(147±71 HU vs 11±20 HU,155±81 HU vs 9±21 HU,P=0.000).The serum levels of MMP-9 and TIMP-1 were significantly higher in A-1 group and A-2 group,B-1 group and B-2 group than in control group(P＜0.01).The area under the ROC curve for MMP-9 and TIMP-1 in diagnosis of unstable plaques was 0.891 and 0.814 respectively.Conclusion MSCTA can accurately detect carotid atherosclerosis in elderly CI patients.However,it is easy to misjudge the nature of plaques.Serum levels of MMP-9 and TIMP-1 can effectively diagnose unstable plaques and can thus be used as an important supplement to MSCTA.