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AJNR - American Journal of Neuroradiology

Published ahead of print on October 8, 2008
doi: 10.3174/ajnr.A1301

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Intracranial Internal Carotid Artery Calcifications: Association with Vascular Risk Factors and Ischemic Cerebrovascular Disease

T.T. de Weert^a, H. Cakir^a, S. Rozie^a, S. Cretier^a, E. Meijering^a,b, D.W.J. Dippel^c and A. van der Lugt^a

^a Department of Radiology, Erasmus MC, University Hospital, Rotterdam, the Netherlands
^b Department of Medical Informatics, Erasmus MC, University Hospital, Rotterdam, the Netherlands
^c Department of Neurology, Erasmus MC, University Hospital, Rotterdam, the Netherlands

View larger version (127K): [in this window] [in a new window]   Fig 1. A curved planar reformatted image from the aortic arch up to the top of the internal carotid artery. The arrows indicate the part of the internal carotid artery at which calcifications are segmented on axial sections. This part comprises the horizontal segment of the petrous internal carotid artery to the top of the carotid artery.

View larger version (77K): [in this window] [in a new window]   Fig 2. A, Regions of interest (region of interest) are drawn on axial images that show calcifications. Care is taken to include the whole calcification and not to include any other high-attenuation structures (eg, skull base). Because a minimum attenuation of 500 HU is defined for the presence of calcifications, lumen can be included in this region of interest, for lumen will not reach such a high level of attenuation. All regions of interest of 1 patient are saved within 1 file. B, The polymeasure software uses the contour file, the 500-HU threshold, and the voxel dimensions (0.234 x 0.234 x 0.6 mm) to create a color overlay image and a statistics table. C, The color overlay image shows which pixels within the region of interest are above the predefined 500-HU threshold (blue) and which are below this threshold (red). D, The statistics table presents the amount of calcium pixels and the calcium volume (cubic millimeters).

View larger version (49K): [in this window] [in a new window]   Fig 3. A, Where calcifications merge with the skull base, it is hard to define the delineation line. B, Changing the window-level setting can then be of help, but observers might still disagree about the exact position of the delineation line. However, the low observer variability assessed in the present study shows that such disagreement only minimally influences total quantification results. Furthermore, the merging of calcifications and skull base prohibits, up to now, fully automated quantification.

View larger version (15K): [in this window] [in a new window]   Fig 4. Bland-Altman plots of calcium volume assessed by 2 observers (Obs1 and Obs2). The horizontal lines express the mean difference and the mean difference ± 2 SDs.

View larger version (16K): [in this window] [in a new window]   Fig 5. Scatterplot of calcium volume versus age for men and women separately. The correlation coefficient for men is 0.548 (P < .001), and for women, 0.501 (P < .001).