High-b-value Diffusion-weighted MR Imaging of Suspected Brain Infarction

• Published in: American journal of neuroradiology : AJNR Vol. 21; no. 10; pp. 1821 - 1829
• Main Authors: Meyer, Joel R, Gutierrez, Arturo, Mock, Bryan, Hebron, Delon, Prager, Jordan M, Gorey, Michael T, Homer, Daniel
• Format: Journal Article
• Language: English
• Published: Oak Brook, IL Am Soc Neuroradiology 01-11-2000; American Society of Neuroradiology
• Subjects: Aged; Biological and medical sciences; Brain; Cerebral Infarction - diagnosis; Echo-Planar Imaging - methods; Female; Humans; Image Processing, Computer-Assisted; Male; Medical sciences; Neurology; Prospective Studies; Vascular diseases and vascular malformations of the nervous system; Human; Cerebral infarction; Nervous system diseases; Central nervous system; Cardiovascular disease; Nuclear magnetic resonance imaging; Cerebral disorder; Vascular disease; Central nervous system disease; Medical imagery; Diagnosis; Diffusion; Cerebrovascular disease; Brain (vertebrata)
• EISSN: 1936-959X
• ISSN: 0195-6108

Recent technological advances in MR instrumentation allow acquisition of whole-brain diffusion-weighted MR scans to be obtained with b values greater than 1,000. Our purpose was to determine whether high-b-value diffusion-weighted MR imaging improved contrast and detection of signal changes in acute and chronic brain infarction.
We prospectively evaluated the MR scans of 30 subjects with a history of possible brain infarction on a 1.5-T MR imager with 40 mT/meter gradients (slew rate 150 T/m/s) by use of the following single-shot echo-planar diffusion-weighted MR sequences: 1) 7,999/ 71.4/1 (TR/TE/excitations, b = 1,000; 2) 999/ 88.1/3, b = 2,500; and 3) 7,999/ 92.1/4, b = 3,000. Diffusion-weighted MR imaging was performed in three orthogonal directions during all sequences. All subjects were scanned with fast fluid-attenuated inversion recovery (FLAIR) (10,006/145/2,200/1 [TR/TE/TI/excitations]) and fast spin-echo T2-weighted (3,650/95/3 [TR/TE/excitations], echo train length, 8). The diagnosis of brain infarction was established by clinical criteria.
Twenty women and 10 men with a mean age of 67.7 years were enrolled in the study. One subject was excluded owing to poor image quality. Twelve of 29 subjects had a clinical diagnosis of acute infarction. All 12 had lesions that were hyperintense on diffusion-weighted images at all three b values; five were cortical and seven subcortical. There was increased contrast of all lesions on high-b-value scans (b = 2,500 and 3,000). Lesions that were hypointense on diffusion-weighted images were identified and evaluated at the three different b values. At b = 1,000, there were 19 hypointense lesions, whereas at b = 2,500 and 3,000 there were 48 and 55 lesions, respectively. On FLAIR and T2-weighted images, these low-signal lesions were predominantly chronic, subcortical, ischemic lesions and lacunar infarcts, but four chronic cortical infarcts, one porencephalic cyst, and one primary brain tumor were also found. Low-signal lesions were also noted to have increased contrast on high-b-value diffusion-weighted scans.
High-b-value diffusion-weighted MR imaging (b = 2,500 or b = 3,000) had no impact on diagnosis of acute infarction. High-b-value diffusion-weighted MR imaging (b = 2,500) combined with diffusion-weighted MR imaging at b = 1,000 improves tissue characterization by increasing the spectrum of observed imaging abnormalities in patients with suspected brain infarction.