ASSESSMENT OF THE RELIABILITY OF THE DETERMINATION OF CAROTID-ARTERY LUMEN SIZES BY QUANTITATIVE IMAGE-PROCESSING OF MAGNETIC-RESONANCE ANGIOGRAMS AND IMAGES

In order to use MR imaging to assess progression or regression of athe rosclerosis, one must have an idea of the reproducibility of the imagi ng and image processing techniques. The ability of dark-blood MRI and semiautomated image processing to reproducibility measure the inner bo undary of the carotid arteries was evaluated and compared with results obtained using bright-blood MRA. MRI and MRA images were obtained for two normal and two diseased volunteers six times each over a short pe riod of time (6 months). The carotid bifurcation was used to align sli ces from different imaging sessions. The area for each vessel (right a nd left common, internal and external carotid artery) was determined f or the six imaging sessions. The standard deviations of each lumen are a normalized to the average area were computed for each vessel segment for each volunteer. For the common, internal, and external carotids, the averaged normalized standard deviations for MRI were 8, 12, and 17 % and for MRA were 6, 8, and 13%, Lumen sizes obtained by MRI and MRA were found to be not statistically different. Eccentric plaques not se en on MRA were visualized by MRI. In conclusion, dark-blood MRI with s emiautomated image processing yields reliable lumen areas that are in agreement with those obtained by MRA.