Detection of carotid artery stenosis using histological specimens: a comparison of CT angiography, magnetic resonance angiography, digital subtraction angiography and Doppler ultrasonography.

BACKGROUND

Carotid endarterectomy (CEA) is accepted as a primary modality to treat carotid stenosis. The accuracy of measuring carotid stenosis is important for indication of the CEA procedure. Different diagnostic tools have been developed and used in the past 2 decades for the diagnosis of carotid stenosis. Only a few studies, however, have focused on the comparison of different diagnostic tools to histological findings of carotid plaque.

METHOD

Patients with internal carotid artery (ICA) stenosis were investigated primarily by computed tomography angiography (CTA). Digital subtraction angiography (DSA), Doppler ultrasonography (DUS) and magnetic resonance angiography (MRA) were performed as well. Atherosclerotic plaque specimens were transversally cut into smaller segments and histologically processed. The slides were scanned and specimens showing maximal stenosis were determined; the minimal diameter and the diameter of the whole plaque were measured. High quality histological specimen and histological measurement was considered to be the prerequisite for inclusion into the analysis. The preoperative findings were compared with histological measurement. CTA and histological measurements were obtained from 152 patients. DSA measurements were available in 138 of these cases, MRA in 107 and DUS in 88. A comparison between preoperative and histological findings was performed. In addition, correlation coefficients were computed and tested.

RESULTS

A significant correlation was found for each of the diagnostic procedures. The strongest correlation coefficient and the best allocation of stenosis into clinical significant groups (<50 %, 50-69 %, ≥70 %) was observed for CTA. Mean differences in the whole cohort between preoperative and histological measurements were as follows: CTA underestimated histological measurement by 2.4 % (based on European Carotid Surgery Trial [ECST] methodology) and 11.9 % (based on North American Symptomatic Carotid Endarterectomy Trial [NASCET] methodology). DSA underestimated the histological measurement by 7 % (ECST) and 12.2 % (NASCET). MRA overestimated the histological measurement by 2.6 % (ECST) and underestimated by 0.6 % (NASCET). DUS overestimated the stenosis by 1.8 %.

CONCLUSIONS

CTA yields the best accuracy in detection of carotid stenosis, provided that all axial slices of the stenosis are checked and carefully analysed. DSA underestimates moderate and mild ICA stenosis, whereas DUS overestimates high-grade ICA stenosis. For MRA, a relatively low correlation coefficient was observed with histological findings. We conclude that CTA-ecst technique is the most reliable technique for carotid stenosis measurement.