The National Institute on Aging and the Alzheimer's Association charged a workgroup with the task of revising the 1984 criteria for Alzheimer's disease (AD) dementia. The workgroup sought to ensure ...that the revised criteria would be flexible enough to be used by both general healthcare providers without access to neuropsychological testing, advanced imaging, and cerebrospinal fluid measures, and specialized investigators involved in research or in clinical trial studies who would have these tools available. We present criteria for all-cause dementia and for AD dementia. We retained the general framework of probable AD dementia from the 1984 criteria. On the basis of the past 27 years of experience, we made several changes in the clinical criteria for the diagnosis. We also retained the term possible AD dementia, but redefined it in a manner more focused than before. Biomarker evidence was also integrated into the diagnostic formulations for probable and possible AD dementia for use in research settings. The core clinical criteria for AD dementia will continue to be the cornerstone of the diagnosis in clinical practice, but biomarker evidence is expected to enhance the pathophysiological specificity of the diagnosis of AD dementia. Much work lies ahead for validating the biomarker diagnosis of AD dementia.
Beyond detecting brain lesions or tumors, comparatively little success has been attained in identifying brain disorders such as Alzheimer’s disease (AD), based on magnetic resonance imaging (MRI). ...Many machine learning algorithms to detect AD have been trained using limited training data, meaning they often generalize poorly when applied to scans from previously unseen scanners/populations. Therefore, we built a practical brain MRI-based AD diagnostic classifier using deep learning/transfer learning on a dataset of unprecedented size and diversity. A retrospective MRI dataset pooled from more than 217 sites/scanners constituted one of the largest brain MRI samples to date (85,721 scans from 50,876 participants) between January 2017 and August 2021. Next, a state-of-the-art deep convolutional neural network, Inception-ResNet-V2, was built as a sex classifier with high generalization capability. The sex classifier achieved 94.9% accuracy and served as a base model in transfer learning for the objective diagnosis of AD. After transfer learning, the model fine-tuned for AD classification achieved 90.9% accuracy in leave-sites-out cross-validation on the Alzheimer’s Disease Neuroimaging Initiative (ADNI, 6,857 samples) dataset and 94.5%/93.6%/91.1% accuracy for direct tests on three unseen independent datasets (AIBL, 669 samples / MIRIAD, 644 samples / OASIS, 1,123 samples). When this AD classifier was tested on brain images from unseen mild cognitive impairment (MCI) patients, MCI patients who converted to AD were 3 times more likely to be predicted as AD than MCI patients who did not convert (65.2% vs. 20.6%). Predicted scores from the AD classifier showed significant correlations with illness severity. In sum, the proposed AD classifier offers a medical-grade marker that has potential to be integrated into AD diagnostic practice.
Neuropathological correlates of Alzheimer's disease (AD) emerge years before dementia. Biomarkers preceding cognitive decline and reflecting the causative processes can potentially aid early ...intervention and diagnosis. Diffusion tensor imaging (DTI) indirectly reflects tissue microstructure. To answer whether DTI is an early biomarker for AD and to explore the relationship between DTI and the established biomarkers of medial temporal lobe atrophy and cerebrospinal fluid (CSF) Aβ(42), T-tau, and P-tau, we longitudinally studied normal controls and patients with subjective (SCI) or mild (MCI) cognitive impairment. 21 controls and 64 SCI or MCI cases recruited from a university-hospital based memory clinic were re-examined after two to three years. FreeSurfer was used for longitudinal processing of morphometric data, and DTI derived fractional anisotropy, radial diffusivity, and mean diffusivity were analyzed in Tract-Based Spatial Statistics. Using regression models, we explored and compared the predictive powers of DTI and CSF biomarkers in regard to cognitive change and atrophy of the medial temporal lobe. Both DTI and CSF biomarkers significantly predicted cognitive decline and atrophy in the medial temporal lobe. In this population, however, DTI was a better predictor of dementia and AD-specific medial temporal lobe atrophy than the CSF biomarkers. The case for DTI as an early biomarker for AD is strengthened, but further studies are needed to confirm these results.
Recently, the lattice Boltzmann (LB) model has been used in medical imaging segmentation as alternatives for level set methods. The advantages of the LB model include its simple programming and the ...fact that it is easily paralleled, which can shorten computing times during real-time processing. However, traditional LB algorithms often fail to segment magnetic resonance (MR) brain images, which usually contain low-contrast intensity levels, noise and bias field. To solve these problems, this paper proposes a new LB algorithm assembled by local statistical region information, which can increase the between-class variances of the foreground and background by reducing intra-class variations and can achieve a better anti-noise performance by smoothing the noise of neighborhood pixels. To test its effectiveness and efficiency, comparison experiments were carried out with other LB and non-LB algorithms. The results show that our algorithm was validated on synthetic images and real MR images with desirable performance in the presence of low-contrast gray levels and noise. It also achieved best segmentation performance (with Dice coefficient 97.9 %) compared to other algorithms (with Dice coefficient 80.33, 58.11, 88.2, 81.77, 96.1 % respectively). In addition, the computing speed of the new algorithm is acceptable (18.65–27.62 s).
Background: Dizziness is a common symptom affecting about 30% of people over the age of 65. Objective: To investigate the hypothesis that structural abnormalities of the brain and cervical cord are ...more common in dizzy than in non-dizzy subjects. Methods: A case–control study of subjects over the age of 65 with and without dizziness: 125 dizzy subjects and 86 non-dizzy subjects were recruited from the community through articles in the local press. Magnetic resonance imaging (MRI) of the brain and neck was performed, and was read by a consultant neuroradiologist blind to the clinical details. Results: All dizzy subjects and all controls had at least one structural abnormality. Cerebral atrophy was found in 86% of dizzy subjects and 85% controls (p = 1.0) At least one white matter lesion was found in 69% of dizzy subjects and 78% controls (p = 0.21). White matter lesions in the midbrain were more common in dizzy than in non-dizzy subjects (22% v 4%, p < 0.001). There were no significant differences in the prevalence of cord compression, cervical subluxation, facet joint degeneration, vertebral artery compression, or vertebral artery occlusion between dizzy and non-dizzy subjects. Conclusions: Structural abnormalities of the brain and neck are common in both dizzy and non-dizzy subjects. “Routine” MRI is unlikely to reveal a specific cause for dizziness. The observation of more frequent white matter lesions in the midbrain in dizzy subjects requires further study to determine whether small vessel changes could cause dizziness in older people.
Abstract
The available literature has shown widespread brain structural and functional changes in patients with generalized anxiety disorder (GAD), of which the deficits in the amygdala-based ...circuits were the most consistent findings and played key role in underpinning the neural mechanisms of GAD. However, ample studies were primarily focused on the amygdala-related structural or functional alterations, considerably less is known about their covariations. To address this issue, we separately calculated the amygdala-based structural covariance (SC) and functional connectivity (FC) in GAD, and then explored their common changes using conjunction analyses. We further tested the influences of the clinical characteristics of patients on the relationship between their amygdala-related structural and functional organization changes using moderation analyses. GAD patients exhibited reduced SC of the bilateral amygdala with regions involved in high order prefrontal, cingulate, and insula cortices, and showed decreased FC of the right amygdala with the bilateral anterior cingulate cortex (ACC) and right temporal pole. SC and FC covariations were observed in the right amygdala-bilateral ACC connectivity and such connectivity was modulated by illness duration of GAD. The amygdala-ACC structural and functional covariations and their interactions with the illness duration of GAD may extend our knowledge of pathological mechanisms of such disease.
Objective. To determine the precision with which intrapartum metabolic acidemia and hypoxic–ischemic encephalopathy (HIE) in term and near-term infants can be identified by neonatal brain imaging.
...Study design. This is a case–control study whose inclusion criteria were neonates born at ≥34 weeks gestation with a cord gas at delivery, suspected neurological abnormalities, and computed tomography (CT) or magnetic resonance (MR) imaging of the brain. Neonates with chromosomal and major congenital malformations were excluded. Brain imaging for neonates with and without metabolic acidemia (pH < 7.0 and base deficit > 12 mM) at birth and HIE were retrospectively reviewed by a neuroradiologist blinded to their clinical course and compared.
Results. There were 54 neonates admitted to the NICU at a single university hospital between 1992 and 2006 that met these inclusion criteria of which 27 had metabolic acidemia at birth. There were 16 diagnosed clinically as having HIE at the time of neonatal discharge, 13 from the acidemic group and 3 from the nonacidemic group. Radiological signs of basal ganglia injury were significantly more common in neonates with metabolic acidemia (29.6%, 3.7%, p = 0.02) and HIE (37.5%, 7.9%, p = 0.01). Logistic regression corrected for gestational age showed that radiological signs of basal ganglia injury could identify the presence of HIE with area under the ROC curve of 0.71, sensitivity 37.5%, specificity 92.1%, positive predictive value 66.7%, and negative predictive value of 77.8%.
Conclusion. Radiological signs of basal ganglia injury on early neonatal imaging are associated with metabolic acidemia and HIE, but is not precise enough to serve as a gold standard in the identification of these conditions.
Image registration is a key component in existing magnetic resonance image processing software packages. Because of nonlinear variability in brain substructures, the commonly used registration ...pipelines applied to the entire brain area may not lead to accurate registration for substructures. This paper presents a two-stage registration approach for a better alignment of brain substructures or regions-of-interest. In the first stage, an affine transformation function is applied to the entire brain area and in the second stage, a nonrigid or deformable transformation function is applied to the substructure of interest. To show the usefulness of this two-stage registration, images from the Brainweb database are examined using normalized mutual information is used to assess the degree of alignment. The comparison results indicate improvements over the commonly used registration approaches.
Cranial magnetic resonance imaging (MRI) has revealed patchy periventricular white matter lesions or "unidentified bright objects" (UBOs) in otherwise neurologically intact individuals. Quantitative ...videofluoroscopic swallowing evaluations and cranial MRI examinations were studied in 49 neurologically normal volunteers (ages 43 to 79 years). Total swallowing duration (TSD) and its subcomponents of oral transit duration (OTD), stage transition duration (STD), and pharyngeal response duration were measured for liquid and semisolid swallows. MRIs were graded from 0, or no UBOs, to 3, or multiple and confluent lesions. The effect of the presence of UBOs on swallowing durational measures and risk factors was analyzed with age differences accounted for statistically (ANCOVA). TSD and OTD for semisolids were significantly differentiated by MRI score (P less than 0.009 and P less than 0.047, respectively). That is, a demonstrable effect was found for an increased number of UBOs on duration of oropharyngeal swallowing in normal individuals.
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