| Objective: To study the clinical significance of CT value changes in the distal end of arterial occlusive lesions of femoral and popliteal artery observed with CT angiography and compared with DSA.Methods: 50 consecutive patients were enrolled retrospectively in this study(mean age, 68.5±8.7 years [standard deviation]; range, 32~83 years; 35 men and 15 women). The reverse attenuation gradient sign was defined as the reverse intra-luminal opacification gradient of vessels distal to the occlusive lesions, which has lower attenuation in the proximal segment and gradually increased attenuation along the vessel. According to DSA findings, the numbers of cases with reverse intra-luminal opacification gradient sign and collateral circulations were counted in groups of chronic total occlusions and subtotal occlusions, and the data were analyzed statistically.Results: There were 50 occlusive lesions displayed on CT angiography. Invasive lower extremity artery angiography was used to confirm 26 chronic total occlusions and 24 subtotal occlusions. The chronic total occlusions group had the reverse attenuation gradient sign significantly more frequently than did the subtotal occlusion group(76.9%(20/26) vs 20.8%(5/24); ?2=13.1,P<0.05). The occurrence rate of collateral vessels demonstrated on CT angiography in groups of chronic total occlusions and subtotal occlusions was 80.8%(21/26)and 29.2%(7/24) respectively, with significant difference between the two, and the former one significantly higher than the latter one(?2=13.5,P<0.05). The diagnostic sensibility and specificity of chronic total occlusions is 92.3% and 70.8% respectively with combined application of the reverse attenuation gradient sign and collateral circulation sign.Conclusion: The reverse attenuation gradient sign represents the retrograde collateral flow distal to an occlusive lesion. This sign is highly specific for chronic total occlusions and helps to differentiate chronic total occlusions from subtotal occlusion. |
