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High-b-value diffusion-weighted MR imaging of suspected brain infarction
J R Meyer1, A Gutierrez, B Mock
1Department of Radiology, Northwestern University Medical School, Evanston, IL, USA.
Background And Purpose:
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.
Methods:
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.
Results:
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.
Conclusion:
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.
Insights
High-b-value diffusion-weighted MRI improves detection of chronic brain infarction lesions. Combining b=1,000 with higher b-values (2,500 or 3,000) enhances tissue characterization in suspected stroke cases.
Area of Science:
- Radiology
- Neuroimaging
- Medical Physics
Background:
- Advancements in MR instrumentation enable whole-brain diffusion-weighted imaging (DWI) with b values exceeding 1,000.
- High b-values may enhance contrast and signal change detection in brain infarction.
Purpose of the Study:
- To evaluate if high-b-value DWI improves contrast and detection of signal changes in acute and chronic brain infarction.
- To compare lesion detection at b=1,000, b=2,500, and b=3,000.
Main Methods:
- Prospective evaluation of 30 subjects with suspected brain infarction using a 1.5-T MRI scanner.
- Acquisition of single-shot echo-planar DWI sequences at b=1,000, b=2,500, and b=3,000.
- Comparison with fast fluid-attenuated inversion recovery (FLAIR) and fast spin-echo T2-weighted images.
Main Results:
- High-b-value DWI (b=2,500 and 3,000) increased contrast for all detected lesions.
- The number of hypointense lesions increased significantly with higher b-values (19 at b=1,000 vs. 48 at b=2,500 and 55 at b=3,000).
- High b-values improved visualization of chronic, subcortical ischemic lesions and lacunar infarcts.
Conclusions:
- High-b-value DWI (b=2,500 or 3,000) did not impact the diagnosis of acute infarction.
- Combining DWI at b=1,000 with higher b-values (b=2,500) improves tissue characterization by expanding the range of detectable abnormalities in patients with suspected brain infarction.