LINE SCAN DIFFUSION IMAGING - CHARACTERIZATION IN HEALTHY-SUBJECTS AND STROKE PATIENTS

OBJECTIVE, Our objective was to evaluate a new scanning method, MR lin e scan diffusion imaging, and assess the apparent diffusion coefficien t in the brains of healthy subjects and stroke patients. SUBJECTS AND METHODS. Line scan diffusion imaging without cardiac gating or head re straints was implemented on low- (0.5 T) and medium- (1.5 T) field-str ength scanners with conventional hardware. Diffusion-weighted images w ere obtained in six healthy subjects and eight stroke patients. Unidir ectional diffusion encoding was used for fast localization of stroke l esions. For further characterization, orthogonal diffusion encoding wa s applied, and the trace of the apparent diffusion coefficient was cal culated. Single-shot diffusion-weighted echoplanar imaging served as t he reference standard. For healthy subjects, imaging was repeated four times on each scanner. Mean and relative precision of the apparent di ffusion coefficient trace values were calculated for each pixel. In st roke lesions and adjacent normal tissue, apparent diffusion coefficien t trace values were determined. RESULTS.In the 108 scans obtained, lin e scan diffusion imaging proved to be robust, virtually free of artifa ct (independent of slice location and orientation), reproducible, and rapid for localization of a stroke. Scan time for 14 slices at 7-mm th ickness was 8 min at 0.5 T and 7 min at 1.5 T. Image qualities with li ne scan diffusion imaging and single-shot diffusion-weighted echoplana r imaging were comparable. At 1.5 T,precision was essentially the same for line scan diffusion imaging (4.3%) and echoplanar imaging (4.7%). With line scan diffusion imaging at 0.5 T and 1.5 T, normal paraventr icular apparent diffusion coefficient trace values averaged 0.71 mu m( 2)/msec, and with echoplanar imaging these values averaged 0.69 mu m(2 )/msec. In acute lesions apparent diffusion coefficient trace values w ere low, and in chronic lesions these values were high. CONCLUSION. Li ne scan diffusion imaging on low- and medium-field-strength MR scanner s equipped with conventional hardware was reliable and practical for m easuring brain apparent diffusion values, which can be applied to the early diagnosis, and hence timely management, of stroke.