Materials and Methods: The regional ethics committee approved the study and written informed consent was obtained from all participants. The study included 25 patients with AD (11 men, 14 women; mean age ± standard deviation [SD], 73 years ± 6; Mini-Mental State Examination (MMSE) score, 24.4 ± 2.7), 24 patients with amnestic MCI (10 men, 14 women; mean age ± SD, 74 years ± 8; MMSE score, 27.2 ± 1.4) and 25 elderly healthy controls (13 men, 12 women; mean age ± SD, 64 years ± 8). For each participant, the hippocampi were automatically segmented on three-dimensional T1-weighted magnetic resonance (MR) images with high spatial resolution. Segmentation was performed by using recently developed software that allows fast segmentation with minimal user input. Group differences in hippocampal volume were assessed by using Student t tests. To obtain robust estimates of P values, the correct classification rate, sensitivity, and specificity, bootstrap methods were used.
Results: Significant hippocampal volume reductions were detected in all groups of patients (–32% in AD patients vs controls, P < .001; –19% in MCI patients vs controls, P < .001; and –15% in AD patients vs MCI patients, P < .01). Individual classification on the basis of hippocampal volume resulted in 84% correct classification (sensitivity, 84%; specificity, 84%) between AD patients and controls and 73% correct classification (sensitivity, 75%; specificity, 70%) between MCI patients and controls.
Conclusion: This automated method can serve as an alternative to manual tracing and may thus prove useful in assisting with the diagnosis of AD.
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]]>Materials and Methods: All patients gave written informed consent for the initial magnetic resonance (MR) studies, and the institutional review board and local research ethics committee waived initial informed consent for the pooled analysis. A total of 190 patients with symptomatic carotid artery disease underwent fluid-attenuated inversion-recovery imaging of the brain and fat-suppressed black-blood T1-weighted MR imaging of the carotid arteries. The volumes of periventricular lesions, subcortical lesions, and total WMHLs were calculated and compared between hemispheres in relation to symptoms and IPH, and their interaction was calculated and compared by using repeated measures three-factorial multivariate analysis.
Results: After exclusion of 12 patients, 178 patients (116 men, 62 women; mean age, 70.2 years ± 8.6 [standard deviation]) remained. There was no significant difference in WMHL volume between the symptomatic and asymptomatic hemispheres, and WMHL volume was not related to the degree of carotid stenosis. The presence of carotid IPH significantly interacted with the interhemispheric WMHL difference (Wilks test, F = 9.95; df = 3; P < .001). Univariate analysis showed larger total and periventricular WMHL volumes (P < .05) in patients with ipsilateral IPH.
Conclusion: Carotid artery disease and leukoaraiosis were associated with features that indicated plaque instability, namely IPH, whereas the degree of stenosis had no effect.
© RSNA, 2008
]]>Materials and Methods: This study was approved by the institutional review board and was compliant with HIPAA regulations. Informed consent was obtained from each subject. The authors identified 54 subjects who underwent antemortem 1H MR spectroscopy and were clinically healthy or had AD-type pathology with low to high likelihood of AD according to National Institute on Aging–Reagan neuropathologic criteria at autopsy. They investigated the associations between 1H MR spectroscopy metabolite measurements and Braak neurofibrillary tangle stage (Braak stage), neuritic plaque score, and AD likelihood, with adjustments for subject age, subject sex, and time between 1H MR spectroscopy and death.
Results: Decreases in N-acetylaspartate–to-creatine ratio, an index of neuronal integrity, and increases in myo-inositol–to-creatine ratio were associated with higher Braak stage, higher neuritic plaque score, and greater likelihood of AD. The N-acetylaspartate–to–myo-inositol ratio proved to be the strongest predictor of the pathologic likelihood of AD. The strongest association observed was that between N-acetylaspartate–to–myo-inositol ratio and Braak stage (RN2 = 0.47, P < .001).
Conclusion: Antemortem 1H MR spectroscopy metabolite changes correlated with AD-type pathology seen at autopsy. The study findings validated 1H MR spectroscopy metabolite measurements against the neuropathologic criteria for AD, and when combined with prior longitudinal 1H MR spectroscopy findings, indicate that these measurements could be used as biomarkers for disease progression in clinical trials.
© RSNA, 2008
]]>Materials and Methods: The medical ethics committee approved this study, and all patients provided informed consent. Fifty-three patients (24 female, 29 male; mean age, 48 years; age range, 14–76 years) with histologically confirmed gliomas were examined with dynamic contrast material–enhanced 1.5-T magnetic resonance (MR) imaging. CBV maps were created and normalized to unaffected white matter (normalized CBV maps). Four neuroradiologists independently measured the distribution of whole-tumor normalized CBVs and analyzed this distribution by classifying the values into area-normalized bins. Glioma grading was performed by assessing the normalized peak height of the histogram distributions. Logistic regression analysis and interobserver agreement were used to compare the proposed method with a hot-spot method in which only the maximum normalized CBV was used.
Results: For the histogram method, diagnostic accuracy was independent of the observer. Interobserver agreement was almost perfect for the histogram method ( = 0.923) and moderate for the hot-spot method ( = 0.559). For all observers, sensitivity was higher with the histogram method (90%) than with the hot-spot method (55%–76%).
Conclusion: Glioma grading based on histogram analysis of normalized CBV heterogeneity is an alternative to the established hot-spot method, as it offers increased diagnostic accuracy and interobserver agreement.
Supplemental material:
© RSNA, 2008
]]>Materials and Methods: Ethics committee approval and informed consent were obtained. Thirty patients with stroke underwent unenhanced CT, CT angiography, and CT perfusion studies at admission. Additionally, CT angiography was performed 24 hours after the stroke, and an unenhanced CT study was performed 5–7 days after the stroke. Five patients were excluded; the remaining patients (10 men, 15 women; mean age, 70 years ± 13 [standard deviation]) were separated into those with recanalization (n = 16) and those without recanalization (n = 9) at 24 hours. For patients with recanalization, the final infarct was outlined on unenhanced CT images obtained 5–7 days after the event and was superimposed on coregistered maps from the CT perfusion study performed at admission. Ischemic white matter tissue (cerebral blood flow [CBF] < 14 mL/min/100 g) was identified at the admission CT perfusion study, and the penumbra was defined as the difference between the ischemic region and the infarct region.
Results: Infarct regions showed a matched decrease in CBF and cerebral blood volume (CBV) at admission, whereas penumbra regions showed a significant (P < .05) decrease in CBF but no change in CBV (P > .05) from contralateral values. A threshold CBF · CBV value of 8.14 was the most sensitive (95%, 20 of 21 regions) and specific (94%, 32 of 34 regions) parameter for differentiating between regions of ischemic white matter that recovered and regions of ischemic white matter that infarcted.
Conclusion: The product of CBF and CBV derived from CT perfusion data provided the best differentiation between regions of ischemic white matter that infarcted and regions of ischemic white matter that recovered 5–7 days after a stroke.
© RSNA, 2008
]]>Materials and Methods: Approval for this retrospective HIPAA-compliant study was obtained from the Institutional Board of Research Associates, with waiver of informed consent. One hundred eighty-nine patients (122 male and 67 female patients; median age, 43 years; range, 4–80 years) were examined with dynamic susceptibility-weighted contrast material–enhanced perfusion magnetic resonance (MR) imaging and were followed up clinically with MR imaging (median follow-up, 334 days). Log-rank tests were used to evaluate the association between relative CBV and time to progression by using Kaplan-Meier curves. Binary logistic regression was used to determine whether age, sex, and relative CBV were associated with an adverse event (progressive disease or death).
Results: Values for the mean relative CBV for patients according to each clinical response were as follows: 1.41 ± 0.13 (standard deviation) for complete response (n = 4), 2.36 ± 1.78 for stable disease (n = 41), 4.84 ± 3.32 for progressive disease (n = 130), and 3.82 ± 1.93 for death (n = 14). Kaplan-Meier estimates of median time to progression in days indicated that patients with a relative CBV of less than 1.75 had a median time to progression of 3585 days, whereas patients with a relative CBV of more than 1.75 had a time to progression of 265 days. Age and relative CBV were also independent predictors for clinical outcome.
Conclusion: Dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging can be used to predict median time to progression in patients with gliomas, independent of pathologic findings. Patients who have HGGs and LGGs with a high relative CBV (>1.75) have a significantly more rapid time to progression than do patients who have gliomas with a low relative CBV.
© RSNA, 2008
]]>Materials and Methods: This HIPAA-compliant study had institutional review board approval, with waiver of informed consent. The authors evaluated the effect of dose modulation on four types of neuroradiologic CT studies: brain CT performed without contrast material (unenhanced CT) in adult patients, unenhanced brain CT in pediatric patients, adult cervical spine CT, and adult cervical and intracranial CT angiography. For each type of CT study, three series of 100 consecutive studies were reviewed: 100 studies performed without dose modulation, 100 studies performed with z-axis dose modulation, and 100 studies performed with x-y-z–axis dose modulation. For each examination, the weighted volume CT dose index (CTDIvol) and dose-length product (DLP) were recorded and noise was measured. Each study was also reviewed for image quality. Continuous variables (CTDIvol, DLP, noise) were compared by using t tests, and categorical variables (image quality) were compared by using Wilcoxon rank-sum tests.
Results: For unenhanced CT of adult brains, the CTDIvol and DLP, respectively, were reduced by 60.9% and 60.3%, respectively, by using z-axis dose modulation and by 50.4% and 22.4% by using x-y-z–axis dose modulation. Significant dose reductions (P < .001) were also observed for pediatric unenhanced brain CT, cervical spine CT, and adult cervical and intracranial CT angiography performed with each dose modulation technique. Image quality and noise were unaffected by the use of either dose modulation technique (P > .05).
Conclusion: Use of dose-modulation techniques for neuroradiology CT examinations affords significant dose reduction while image quality is maintained.
Supplemental material:
© RSNA, 2008
]]>Materials and Methods: All patients gave written informed consent for this institutional ethics committee–approved study. Thirteen patients (seven men, six women; age range, 29–69 years) with biopsy-proved low-grade glioma treated only with antiepileptic drugs were examined longitudinally with susceptibility-weighted perfusion, T2-weighted, fluid-attenuated inversion recovery, and high-dose contrast material–enhanced T1-weighted MR imaging at 6-month intervals to date or until malignant transformation was diagnosed. Student t tests were used to determine differences in rCBV values between "transformers" and "nontransformers" at defined time points throughout study follow-up.
Results: Seven patients showed progression to high-grade tumors between 6 and 36 months (mean, 22.3 months), and disease in six patients remained stable over a period of 12–36 months (mean, 23 months). Transformers had a slightly (but not statistically significantly) higher group mean rCBV than nontransformers at the point of study entry (1.93 vs 1.31). In nontransformers, the rCBV remained relatively stable and increased to only 1.52 over a mean follow-up of 23 months. In contrast, transformers showed a continuous increase in rCBV up to the point of transformation, when contrast enhancement became apparent on T1-weighted images. The group mean rCBV was 5.36 at transformation but also showed a significant increase from the initial study at 12 months (3.14, P = .022) and at 6 months (3.65, P = .049) before transformation. Rates of rCBV change between two successive time points were also significantly higher in transformers than in nontransformers.
Conclusion: In transforming low-grade glioma, susceptibility-weighted MR perfusion imaging can demonstrate significant increases in rCBV up to 12 months before contrast enhancement is apparent on T1-weighted MR images.
© RSNA, 2008
]]>Materials and Methods: This study was approved by the institutional review board, and informed consent was obtained. Diffusion-tensor imaging data with an isotropic voxel size of 1.9 mm3 were acquired at 3 T in 38 healthy volunteers (age range, 18–88 years; 18 women). Quantitative fiber tracking was used to calculate fractional anisotropy (FA) and mean diffusivity values, eigenvalues (1, 2, and 3), the number of fiber projections, and the number of fiber projections per voxel for three-dimensional reconstructed association, callosal, projection, and total brain fibers. Bivariate linear regression models were used to analyze correlations. Significant differences between correlations were assessed with the Hotelling-Williams test.
Results: For FA, the strongest degradation in association fibers and no significant changes in projection fibers were observed. The difference in correlation was significant (P = .002). The number of fiber projections and the number of fiber projections per voxel showed strong to moderate negative correlations that were dependent on age (P < .001) in the three fiber structures and total brain fibers, with the exception of the number of fiber projections per voxel in projection fibers, which showed no significant correlation. The decrease in the number of fiber projections was significantly greater (P = .043) in projection fibers than in total brain fibers, whereas the decrease in the number of fiber projections per voxel was significantly weaker (P = .005). Association fibers showed the largest changes per decade of age for FA (–1.13%) and for the number of fiber projections per voxel (–4.7%), whereas callosal fibers showed the largest changes per decade of age for the number of fiber projections (–10.4%).
Conclusion: Quantitative fiber tracking enables identification of differences in diffusivity and fiber characteristics due to normal aging.
© RSNA, 2008
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