PubMed · 12577039
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Hideaki Hayashi. 2002. [Diffusion tensor imaging analysis using PC version Dr.View/LINUX].. https://doi.org/10.6009/jjrt.kj00000921559
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BACKGROUND AND PURPOSE: Although diffusion-weighted MRI (DWI) has demonstrated clear superiority over other conventional imaging modalities in the detection of hyperacute cerebral ischemia, its value in the evaluation of patients with transient symptoms has received only limited attention. We assessed the utility of DWI in patients with transient ischemic attack (TIA) to further evaluate the usefulness of this technique in these individuals. METHODS: A retrospective analysis was performed on all patients entered in the Stanford Stroke Center database during 1997-2001 who were clinically diagnosed with a TIA and who had also undergone a DWI scan or=1 hour, 16 times more likely to have had motor deficits, and 25 times more likely to have had aphasia than patients with negative DWI scans. The combination of all 3 symptoms was 100% specific for an abnormality on DWI. In 7 of 16 cases (44%), a DWI abnormality was present on both DWI and conventional imaging (T2-weighted imaging or fluid-attenuated inversion recovery [FLAIR]). In all of these cases the DWI clarified the extent or acuity of the lesion (n=7) or identified additional lesions not detected by conventional imaging (n=9). CONCLUSIONS: In TIA patients, symptom duration >or=1 hour, motor deficits, and aphasia were each independently correlated with detecting an abnormality with DWI. DWI was also helpful in differentiating between chronic versus acute lesions. These data may be of value in identifying those TIA patients for whom MRI evaluation with DWI is of greatest clinical utility.
BACKGROUND AND PURPOSE: The traditional definition of transient ischemic attack (TIA), based on an arbitrary time criterion of symptom resolution within 24 hours, is problematic because a large number of patients with traditionally defined TIAs have a relevant cerebral infarction on brain imaging. The objective of this study was to characterize the epidemiological impact of adopting a tissue-based definition of TIA. METHODS: Estimates of the annual US incidence of traditionally defined transient ischemic attacks were abstracted from the literature. Models were then constructed for determining the frequency of brain injury in traditionally defined TIAs, derived from recent human studies of MR diffusion-weighted imaging (DWI) in transient cerebral ischemia. RESULTS: Traditionally defined US TIA annual incidence rates ranged from 37 to 107 per 100,000 per year. Across 5 series, the raw frequency of DWI positivity in traditionally defined TIAs was 44%. Adjusting for an overrepresentation of longer-duration TIAs in MR series yielded an expected frequency of diffusion MRI positivity of 33% in unselected, traditionally defined TIAs. Applying this model to the US population in the year 2000 showed that adopting a tissue-based definition of TIA would decrease the annual number of events classified as TIAs from 179,840 to 120,493 and increase events classified as strokes from 821,181 to 880,520. CONCLUSIONS: Adopting a tissue-based definition of transient ischemic attack would reduce estimates of the annual incidence of TIA by 33% (sensitivity analysis range, 19% to 44%) and increase estimates of the annual incidence of stroke in the United States by 7% (range, 4% to 10%).
PURPOSE: To evaluate the usefulness of echo-planar MR imaging for assessing the thyroid function and confirm the clinical use of MR imaging for thyroid diseases. MATERIALS AND METHODS: Thirty-four patients with a variety of thyroid disorders (24 Graves disease; five subacute thyroiditis; five Hashimoto thyroiditis) were examined using T1-, T2-, and diffusion-weighted magnetic resonance (MR) imaging and thyroid scintigraphy with Tc-99m pertechnetate. RESULTS: The ADC values obtained from the diffusion-weighted images of the patients with Graves disease were significantly higher than those of patients with subacute hyroiditis and Hashimoto thyroiditis, though no difference among those disorders was observed on T1- and T2-weighted images. Based on the ADC value, anisotropy was not observed in the thyroid gland. An ADC value of 1.82 x 10(-3) mm(2)/second or higher indicated the presence of Graves disease (sensitivity 75%, specificity 80%). CONCLUSION: Diffusion-weighted MR images may be of value for the diagnosis of thyroid diseases and could be clinically important in the evaluation of thyroid function.