Evaluation of small ischemic lesions after carotid artery stenting: the usefulness of thin-slice diffusion-weighted MR imaging.

Introduction: There has been concern regarding the usefulness of diffusion-weighted imaging (DWI) to evaluate the ischemic lesions associated with carotid artery stent placement (CAS). Some small lesions may be detected not by standard DWI but by thin-slice DWI alone, since most of the cerebral lesions are very small in size and clinically silent. The purpose of this study is to compare the detectability of the small ischemic lesions after CAS by standard and thin-slice DWI.

Methods: Both standard DWI with slice thickness of 6 mm and thin-slice DWI with slice thickness of 2 mm were obtained at the same MR examination within 2 to 7 days after 20 procedures of CAS in 17 patients. Number and measured diameter size of the detected lesions on both DWI were compared.

Results: All CAS procedures in 17 patients were successfully completed. The focal ischemic lesions were detected in 14 of 20 on thin-slice DWI and seven examinations on standard DWI. The total numbers of hyperintense lesions were 31 on thin-slice DWI and ten on standard DWI (p < 0.001). The sizes of these ten lesions on thin-slice DWI were larger than those of standard DWI, and the mean size of the thin-slice DWI and that of standard DWI were significantly different (p < 0.005).

Conclusion: Thin-slice DWI was able to detect small cortical lesions better than standard DWI. Thin-slice DWI may be useful to evaluate small silent ischemic lesions after CAS.