The value of b required to avoid T2 shine-through from old lucunar infarcts in diffusion-weighted imaging |
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Authors: | Geijer B Sundgren P C Lindgren A Brockstedt S Ståhlberg F Holtås S |
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Institution: | (1) Department of Radiology, University Hospital, 22 185 Lund, Sweden e-mail: bo.geijer@drad.lu.se Tel.: + 46-46-17 30 65 Fax: + 46-46-2 11 69 56, SE;(2) Department of Neurology, University Hospital, 22 185 Lund, Sweden, SE;(3) Department of Radiation Physics, University Hospital, 22 185 Lund, Sweden, SE |
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Abstract: | Multiple small infarcts of different ages are common in small-vessel disease. Diffusion-weighted imaging (DWI) is a powerful
method for discriminating new from chronic lesions. This can be done on the diffusion-weighted images provided that b is sufficiently
high. Our purpose was to determine that critical value of b. We reviewed DWI from a previous study of acute, mainly lacunar
strokes, and selected 18 old lacunar infarcts, well defined on uncoded images with b 0 s/m2 (i. e., T2-weighted images) but invisible on DWI with b 1200 × 106 s/m2. We used a 1.5 tesla imager and single-shot echo-planar technique. We had seven separate acquisitions with echo time 123
ms and b in steps between 0 and 1200 × 106 s/m2. Two neuroradiologists blinded to the selection of lesions carried out two different lesion-detection procedures, thereby
testing each lesion four times, giving a total of 72 tests of b values. The results were consistent, indicating a level for
detection of 800 × 106 s/m2 in two tests, 400–600 × 106 s/m2 in 65 tests and at lower values in the remainder. For imagers up to 1.5 tesla, at long repetition times and an echo time
up to 120 ms T2-shine through of old lacunar infarcts can be avoided using b of 1000 × 106 s/m2.
Received: 5 July 2000 Accepted: 6 December 2000 |
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Keywords: | Lacunar infarcts Diffusion-weighted imaging |
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