BACKGROUND AND PURPOSE:Accurate in vivo quantification of myelin remains challenging despite advances in MRI. We evaluated three-dimensional synthetic MRI-derived myelin volume fraction from three-dimensional quantification using an interleaved Look-Locker acquisition sequence with T2 preparation pulse (3D-QALAS) by comparing it with inhomogeneous magnetization transfer ratio, myelin water fraction, and the T1-weighted/T2-weighted ratio in healthy volunteers and patients with multiple sclerosis. MATERIALS AND METHODS:Thirty-one healthy volunteers and 33 consecutive patients with multiple sclerosis underwent 3T MRI including 3D-QALAS, 3D inhomogeneous magnetization transfer imaging, and 2D multi-echo spin-echo imaging for myelin water fraction. Synthetic T1-weighted/T2-weighted ratio maps were generated from quantitative R1, R2, and proton density data. Lesions were segmented using a deep learning-based method, and periplaque regions were defined by 2-voxel isotropic dilation. Atlas-based ROI analyses in normal-appearing brain tissue were performed using repeated-measures correlation. WM lesion-centered analyses were performed to compare metric differences relative to normal-appearing white matter using linear mixed-effects models. RESULTS:In normal-appearing brain tissue pooled across patients and volunteers, myelin volume fraction demonstrated strong overall repeated-measures correlations with the inhomogeneous magnetization transfer ratio (r = 0.86; 95% CI, 0.85-0.87) and the T1-weighted/T2-weighted ratio (r = 0.89; 95% CI, 0.88-0.89), and more modest correlations with myelin water fraction (r = 0.63; 95% CI, 0.61-0.64). The inhomogeneous magnetization transfer ratio-myelin water fraction correlation was r = 0.60 (95% CI, 0.58-0.62). This overall ranking was preserved in volunteers and patients analyzed separately, and Spearman analyses showed a similar pattern. In WM lesion-centered analyses, values relative to normal-appearing WM were lowest for myelin volume fraction (44.2% in plaque, 75.4% in periplaque), followed by the T1-weighted/T2-weighted ratio (56.5%, 77.3%), the inhomogeneous magnetization transfer ratio (74.7%, 87.8%), and myelin water fraction (93.4%, 98.3%). CONCLUSIONS:3D-QALAS-derived myelin volume fraction demonstrated strong overall concordance with the inhomogeneous magnetization transfer ratio in normal-appearing brain tissue and greater lesion-associated deviation from normal-appearing white matter than the other myelin-sensitive metrics. These findings support 3D-QALAS-derived myelin volume fraction as a promising volumetric biomarker of myelin integrity with whole-brain coverage suitable for routine clinical application.

We evaluated whether, compared with conventional deep learning reconstruction (DLR) and zero-filling interpolation (ZIP), super-resolution DLR (SR-DLR) enhances the visualization of vestibular schwannomas and cranial nerves in three-dimensional constructive interference in steady state (3D-CISS) magnetic resonance (MR) imaging. This retrospective study analyzed 39 patients with vestibular schwannomas who underwent 3T MR imaging with 3D-CISS. Axial images were reconstructed using SR-DLR, DLR, and ZIP. Three readers independently evaluated tumor depiction, depiction of facial and vestibulocochlear nerves, sharpness, noise, artifacts, and diagnostic acceptability. Quantitative indicators included edge rise distance (ERD) and edge rise slope (ERS) measured along a linear region of interest (ROI) drawn perpendicularly across the tumor–cistern cerebrospinal fluid (CSF) boundary, and signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and contrast ratio (CR) calculated from circular ROIs (3–5 mm) placed in the tumor and prepontine CSF. SR-DLR significantly improved visualization of vestibular schwannoma and facial and vestibulocochlear nerves compared with ZIP (p < 0.001). Nerve depiction ratings varied between readers when comparing SR-DLR and DLR. SR-DLR yielded significantly better sharpness, lower ERD and higher ERS than both DLR and ZIP (p < 0.001). Artifacts showed no significant differences. No clear deterioration in noise was noted. Objectively, SR-DLR showed significantly higher CR than DLR (p = 0.023) and ZIP (p < 0.001). SNR and CNR were significantly higher with SR-DLR than ZIP, but comparable to DLR. SR-DLR improves sharpness and lesion conspicuity on 3D-CISS imaging without a clear increase in artifacts or noise compared with ZIP.

Accurate identification of peripancreatic arteries in pancreatic ductal adenocarcinoma (PDAC) is essential for determining surgical strategy and prognosis. This study compared super-resolution deep learning reconstruction (SR-DLR) with normal-resolution deep learning reconstruction (NR-DLR) and hybrid iterative reconstruction (HIR) in the depiction of peripancreatic arteries in patients with PDAC undergoing pancreatic dynamic CT. This retrospective study included 40 patients (mean age, 70.8 ± 9.3 years) with pathologically confirmed PDAC who underwent pancreatic dynamic CT. Images were reconstructed using SR-DLR, NR-DLR, and HIR. In quantitative image analyses, CT attenuation, image noise, contrast-to-noise ratio (CNR), edge rise slope (ERS), and edge rise distance (ERD) were assessed. In qualitative image analyses, five radiologists independently evaluated arterial depiction of major arteries and small peripancreatic arteries, tumor–vessel interface, image noise, image sharpness, diagnostic acceptability, and tumor conspicuity. Statistical analyses were performed using paired t-tests and the Wilcoxon signed-rank test with Bonferroni correction. SR-DLR showed higher CT attenuation, lower image noise, and higher CNR than NR-DLR and HIR (all p < 0.001). For both the superior mesenteric artery and pancreatic parenchyma, ERS was higher with SR-DLR than with NR-DLR and HIR (all p ≤ 0.002), whereas ERD was lower than with NR-DLR and HIR (all p ≤ 0.001). In qualitative image analyses, SR-DLR achieved the highest scores for small peripancreatic arteries and all qualitative items except for the depiction of major peripancreatic arteries (p < 0.001). SR-DLR improved quantitative image quality and enhanced the qualitative depiction of small peripancreatic arteries and the tumor–vessel interface in pancreatic dynamic CT for patients with PDAC.

OBJECTIVES:We aimed to compare microstructural white matter alterations in multiple sclerosis (MS), anti-aquaporin-4 antibody-positive neuromyelitis optica spectrum disorders (AQP4-NMOSD), and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) using advanced quantitative MRI. METHODS:This retrospective study included 84 participants (24 MS, 18 AQP4-NMOSD, 20 MOGAD, and 22 healthy controls). Quantitative MR relaxometry and multi-shell diffusion-weighted imaging were acquired at 3 T to derive myelin volume fraction (MVF), axonal volume fraction, g-ratio, and diffusion tensor metrics. Normal-appearing white matter (NAWM) was analyzed in all patients, and plaque-based analyses were performed in patients with focal white matter lesions (20 MS, 8 AQP4-NMOSD, 8 MOGAD). Diagnostic performance was assessed using receiver operating characteristic (ROC) analyses. RESULTS:In NAWM, MS showed significantly lower fractional anisotropy than MOGAD or controls (P < 0.05), and AQP4-NMOSD exhibited lower MVF than MOGAD (P < 0.05). Among patients with lesions, plaques in MS had significantly lower MVF and higher g-ratio than those in AQP4-NMOSD (P < 0.0001) and MOGAD (P < 0.05). Plaques in AQP4-NMOSD showed a lower g-ratio than MOGAD (P < 0.01). Univariate ROC analyses revealed that plaque g-ratio distinguished AQP4-NMOSD from MS (AUC 0.92 [95%CI, 0.82-1.00], sensitivity 100.0%, specificity 75.0%) and from MS + MOGAD (AUC 0.88 [0.77-0.99], sensitivity 100.0%, specificity 75.0%). A multivariate model combining NAWM and plaque metrics further improved discrimination (AUC 0.95 [0.88-1.00], sensitivity 75.0%, specificity 95.0%, and AUC 0.91 [0.81-1.00], sensitivity 50.0%, specificity 92.9%). CONCLUSION:Quantitative MRI metrics-especially MVF and g-ratio-demonstrate distinct microstructural profiles among MS, AQP4-NMOSD, and MOGAD, enabling improved disease differentiation.

This case report shows that paramagnetic rim lesions (PRLs), markers of chronic active lesions in multiple sclerosis, vary in visibility depending on scan-parameters of susceptibility-weighted imaging (SWI). Routine SWI for microbleed detection with low flip angle (FA) failed to depict PRLs, while longer TE and higher FA improved visibility. Phase images consistently visualized PRLs. These findings underscore the need to optimize TE and FA, as suboptimal SWI settings may hinder PRL detection.

OBJECTIVE:We aimed to elucidate the correlation between cognitive function and relaxation rates of the cerebral cortex in the early stages of cognitive decline. METHODS:Brain MRI was performed on 97 community-dwelling elderly participants aged 65-84 years. R1 (1/T1) and R2 (1/T2) maps were obtained with synthetic MRI (SyMRI). Cognitive function was evaluated using the Japanese version of the Montreal Cognitive Assessment (MoCA). Participants were categorized into mild cognitive impairment (n = 47) and healthy control (n = 50) groups. Voxel-based quantification (VBQ) and voxel-based morphometry (VBM) analyses were conducted using two-sample t-tests and multiple regression models, with age and sex as covariates. RESULTS:VBQ revealed a significant negative correlation between R1 values and MoCA visuospatial/executive score in the bilateral frontal pole and left superior frontal gyrus (family-wise error-corrected p < 0.05). No significant correlations were found between R2 values and visuospatial/executive score. The multiple regression analysis for VBM showed no significant correlations, and the two-sample t-tests for both VBQ and VBM revealed no significant group differences. CONCLUSION:Visuospatial/executive impairment correlated with higher R1 and R2 values in the frontal cortex, suggesting their potential as biomarkers for early cognitive decline.

Radiation dose is a major concern in dynamic myocardial CT perfusion scan. The purpose of this study was to investigate the effect of reducing the sampling rate on quantitative and semi-quantitative values. This single-center prospective study included 45 patients with type 2 diabetes mellitus (mean age, 58 ± 10 years [SD]; 30 men). Stress and rest dynamic CT perfusion scans were performed every heartbeat for 25 s. Coronary flow reserve (CFR) was calculated as the ratio of stress to rest myocardial blood flow. The summed difference score (SDS) was evaluated using stress and rest myocardial blood flow. CFR and SDS values were compared using the original dataset (1RR) and datasets with reduced sampling rates of 2 and 3 RR intervals (2RR and 3RR). Simulated effective doses were also compared. The mean CFR using the 1RR dataset was 5.89 ± 2.53, unchanged using the 2RR dataset (5.67 ± 2.42, p = 0.08) and decreased to 5.47 ± 2.45 (p = 0.001) using the 3RR dataset. The median SDS (interquartile range) using the 1RR, 2RR and 3RR datasets were 0 (0, 5.75), 0.5 (0, 7) and 0 (0, 6), respectively, with no difference (p > 0.05). The effective doses simulated using the 2RR and 3RR data were 6.7 ± 1.4 mSv and 5.8 ± 1.3 mSv, respectively, significantly lower than the original dose (9.2 ± 1.8 mSv, p < 0.001). A sampling rate of 2RR might be feasible for both semi-quantitative and quantitative evaluation in dynamic myocardial CT perfusion exams.

The aging process induces a variety of changes in the brain detectable by magnetic resonance imaging (MRI). These changes include alterations in brain volume, fluid-attenuated inversion recovery (FLAIR) white matter hyperintense lesions, and variations in tissue properties such as relaxivity, myelin, iron content, neurite density, and other microstructures. Each MRI technique offers unique insights into the structural and compositional changes occurring in the brain due to normal aging or neurodegenerative diseases. Age-related brain volume changes encompass a decrease in gray matter and an increase in ventricular volume, associated with cognitive decline. White matter hyperintensities, detected by FLAIR, are common and linked to cognitive impairments and increased risk of stroke and dementia. Tissue relaxometry reveals age-related changes in relaxivity, aiding the distinction between normal aging and pathological conditions. Myelin content, measurable by MRI, changes with age and is associated with cognitive and motor function alterations. Iron accumulation, detected by susceptibility-sensitive MRI, increases in certain brain regions with age, potentially contributing to neurodegenerative processes. Diffusion MRI provides detailed insights into microstructural changes such as neurite density and orientation. Neurofluid imaging, using techniques like gadolinium-based contrast agents and diffusion MRI, reveals age-related changes in cerebrospinal and interstitial fluid dynamics, crucial for brain health and waste clearance. This review offers a comprehensive overview of age-related brain changes revealed by various MRI techniques. Understanding these changes helps differentiate between normal aging and pathological conditions, aiding the development of interventions to mitigate age-related cognitive decline and other symptoms. Recent advances in machine learning and artificial intelligence have enabled novel methods for estimating brain age, offering also potential biomarkers for neurological and psychiatric disorders.

ABSTRACT:The aging process induces a variety of changes in the brain detectable by magnetic resonance imaging (MRI). These changes include alterations in brain volume, fluid-attenuated inversion recovery (FLAIR) white matter hyperintense lesions, and variations in tissue properties such as relaxivity, myelin, iron content, neurite density, and other microstructures. Each MRI technique offers unique insights into the structural and compositional changes occurring in the brain due to normal aging or neurodegenerative diseases. Age-related brain volume changes encompass a decrease in gray matter and an increase in ventricular volume, associated with cognitive decline. White matter hyperintensities, detected by FLAIR, are common and linked to cognitive impairments and increased risk of stroke and dementia. Tissue relaxometry reveals age-related changes in relaxivity, aiding the distinction between normal aging and pathological conditions. Myelin content, measurable by MRI, changes with age and is associated with cognitive and motor function alterations. Iron accumulation, detected by susceptibility-sensitive MRI, increases in certain brain regions with age, potentially contributing to neurodegenerative processes. Diffusion MRI provides detailed insights into microstructural changes such as neurite density and orientation. Neurofluid imaging, using techniques like gadolinium-based contrast agents and diffusion MRI, reveals age-related changes in cerebrospinal and interstitial fluid dynamics, crucial for brain health and waste clearance. This review offers a comprehensive overview of age-related brain changes revealed by various MRI techniques. Understanding these changes helps differentiate between normal aging and pathological conditions, aiding the development of interventions to mitigate age-related cognitive decline and other symptoms. Recent advances in machine learning and artificial intelligence have enabled novel methods for estimating brain age, offering also potential biomarkers for neurological and psychiatric disorders.

PurposeThis study aimed to evaluate the relationship between sleep quality as assessed using the Pittsburgh Sleep Quality Index (PSQI) and the index of diffusivity along the perivascular space (ALPS index), a possible indirect indicator of glymphatic system activity.Materials and methodsThis study included the diffusion magnetic resonance imaging (MRI) data of 317 people with sleep disruption and 515 healthy controls (HCs) from the Human Connectome Project (WU-MINN HCP 1200). The ALPS index was calculated automatically based on diffusion tensor image analysis (DTI)-ALPS of diffusion MRI. The ALPS index of the sleep disruption and HC groups was compared using general linear model (GLM) analysis with covariates, such as age, sex, level of education, and intracranial volume. In addition, to confirm the relationship between sleep quality and the ALPS index in the sleep disruption group as well as evaluate the effect of each PSQI component on the ALPS index, correlation analyses between the ALPS indices and PSQI scores of all the components and between the ALPS index and each PSQI component was performed using GLM analysis with the abovementioned covariates, respectively.ResultsThe ALPS index was significantly lower in the sleep disruption group than in the HC group (p = 0.001). Moreover, the ALPS indices showed significant negative correlations with the PSQI scores of all the components (false discovery rate [FDR]-corrected p < 0.001). Two significant negative correlations were also found between the ALPS index and PSQI component 2 (sleep latency, FDR-corrected p < 0.001) and 6 (the use of sleep medication, FDR-corrected p < 0.001).ConclusionOur findings suggest that glymphatic system impairment contributes to sleep disruption in young adults.

This study evaluated the frequency, and effect of physiological 2-deoxy-2-[fluorine-18] fluoro-D-glucose (FDG) tracer injection and its association with the penetration rates of mobile devices. This retrospective analysis included 213 patients (mean age ± standard deviation, 66.2 ± 14.1 years; range 23–93 years; 125 men) who underwent FDG-positron emission tomography examination. Elevated FDG activity in the thenar eminence with maximum standardized uptake value (SUVmax) ≥ 2.5 was considered positive. Differences according to age, sex, laterality, and tracer injection side were evaluated using Fisher’s exact test. Associations were assessed using Pearson’s correlation coefficient. Twenty-three percent (49/213) of the patients had elevated FDG activity in the thenar eminence (mean SUVmax, 3.50 ± 1.04; range 2.5–6.3), including 18 with bilateral findings. No significant difference existed according to age (< 50 years vs. 50–69 years vs. ≥ 70 years), sex, laterality, or tracer injection side. No significant correlation existed between penetration rates of mobile devices and the findings (p = 0.08). Elevated FDG activity in the thenar eminence occurs in adults, regardless of age, sex, laterality, or tracer injection side. This should be considered a common physiological change that does not warrant any further investigation.

Abstract Although differentiating benign and malignant thymic epithelial lesions is important to avoid unnecessary treatment and predict prognosis, it is challenging because of overlaps in the chest computed tomography (CT) findings. In this study, we investigated whether the diameter of the thymic vein and other CT findings could differentiate between benign (thymoma and thymic cysts) and malignant (thymic carcinoma, [TCa]) lesions. We conducted a retrospective study across two tertiary referral hospitals in Japan between November 2009 and June 2018. We included 12 patients with TCa, 34 patients with thymomas, and 17 patients with thymic cysts. We analyzed the receiver operating characteristic (ROC) curve to determine the best cut-off values and performed univariate and multivariate analyses of CT findings to distinguish TCa from other benign lesions. Post-hoc analysis was performed for the maximum short axis of the thymic vein using the Mann–Whitney U test, and the number of the maximum short axis of the thymic vein ≥ the cutoff was determined using the Fisher exact test with a family-wise error-correction using Bonferroni's method. ROC analysis showed that a maximum short axis of the thymic vein ≥2 mm was considerably more frequent in TCa than in the other lesions (P < .001 for both), with 83% sensitivity and 86% specificity. Univariate and multivariate analyses revealed the association with TCa of the number of the maximum short axis of the thymic vein ≥2 mm (P = .005, multivariate generalized linear model analysis), ill-defined margin (P = .001), and mediastinal lymphadenopathy (P < .001). Thymic vein diameter was in descendimg order of TCa > thymoma > thymic cysts with statistically significant differences between the groups (Ps < .05). Thymic vein diameter was significantly longer in TCa than in thymoma and thymic cysts. Measurement of the maximum short axis of the thymic vein could be a powerful diagnostic tool to differentiate TCa from thymoma and thymic cysts.

ACTA2-related vasculopathy is an autosomal dominant genetic disorder characterized by aortic aneurysms and dissection, and limb artery lesions are rare. We report a case of transcatheter arterial embolization for a pseudoaneurysm of a deep femoral artery in a patient with presumptive ACTA2-related vasculopathy. A 58-year-old woman was presumed to have an ACTA2 mutation based on her history of aortic diseases and family history of ACTA2 mutations. During follow-up, contrast-enhanced computed tomography for aortic diseases revealed occlusion and vessel wall abnormalities of the bilateral deep femoral arteries. Two weeks later, she complained of acute right inguinal pain without any triggering factors, and contrast-enhanced computed tomography revealed a pseudoaneurysm of the right deep femoral artery. Vascular fragility due to ACTA2 mutation was believed to be the cause of the pseudoaneurysm. Transcatheter arterial embolization was successfully performed and no rebleeding occurred during 1.5 years after the transcatheter arterial embolization.

The central sulcus is an important landmark in the brain. This study aimed to investigate the distinctive signal of the paracentral lobule (PL) on T1-weighted images (T1WIs; the white PL sign) and evaluate its usefulness as a new method of identifying the central sulcus. T1WIs of the brain of 96 participants (age, 58.9 ± 17.9 years; range, 8–87 years) scanned at 3-T MR system were retrospectively reviewed. First, we qualitatively analyzed the signal of the cortex of the PL by comparing it with that of the ipsilateral superior frontal gyrus on a 4-point grading score. Second, we compared the cortical signal intensity and gray/white-matter contrast between the PL and superior frontal gyrus. Third, we evaluated the usefulness of the PL signal for identifying the central sulcus. The PL cortex was either mildly hyperintense (grade 2) or definitely hyperintense (grade 3) in comparison with that of superior frontal cortex in all participants. The signal intensity of the PL cortex was significantly higher than that of the superior frontal cortex (p < 0.001), whereas the gray/white-matter contrast of the PL was weaker than that of the superior frontal gyrus (p < 0.001). The central sulci were identified with 94.3% accuracy (181/192) using the new method. The white PL sign may be helpful in identifying the central sulcus, and this approach can be recognized as a new method for identification of the central sulcus.

Neurobiological mechanisms for social skills acquisition in schizophrenia remain largely unknown. We investigated whether an electrophysiological index of cognitive function predicts the degree of training-related social skills improvement in schizophrenia. Thirteen patients with schizophrenia underwent assessment of mismatch negativity (MMN) event-related potentials, followed by participation in a 3-month social skills training. Larger right frontal/temporal MMN current density values elicited by across-phoneme change were significantly associated with individual degrees of improvement in total social skills scores as assessed by a structured role play test. Although preliminary, these results suggest that phonetic MMN could be an index of social skills acquisition in patients with schizophrenia.

The auditory mismatch negativity (MMN) or its magnetic counterpart (magnetic mismatch field, MMF) has been widely used to assess the ability of stimulus-driven change detection process in humans. The authors evaluated the similarity of inter-individual variation of the response strength between MMN and MMF recordings. Three types of MMN or MMF were recorded in ten healthy subjects: change in duration of pure-tone stimuli, change in duration of the Japanese vowel /a/, and difference between the Japanese vowels /a/ and /o/. There was no significant correlation between MMN amplitude and MMF strength under any condition and in either hemisphere. These results suggest that widely used indices of MMN in the two technologies, i.e., EEG-amplitude and MEG-ECD may not be proportional in an individual. To further clarify the differential significance of recording MMN/MMF may be important to establish MMN/MMF as clinical indices of individual ability of preattentive stage of auditory processing.

Objective: Autism is a form of pervasive developmental disorder in which dysfunction in interpersonal relationships and communication is fundamental. This study evaluated neurophysiological abnormalities at the basic level of language processing, i.e. automatic change detection of speech and non-speech sounds, using magnetoencephalographic recording of mismatch response elicited by change in vowels and tones.Methods: The auditory magnetic mismatch field (MMF) was evaluated in 9 adults with autism and 19 control subjects using whole-head magnetoencephalography. The MMF in response to the duration change of a pure tone or vowel /a/ and that in response to across-phoneme change between vowels /a/ and /o/, were recorded.Results: The groups were not significantly different in MMF power under any conditions. However, the autism group showed a left-biased latency prolongation of the MMF particularly under the across-phoneme change condition, and this latency delay was significantly associated with greater symptom severity.Conclusions: These results suggest that adults with autism are associated with delayed processing for automatic change detection of speech sounds. These electrophysiological abnormalities at the earliest level of information processing may contribute to the basis for language deficits observed in autism.Significance: These results provide the first evidence for delayed latency of phonetic MMF in adults with autism. (c) 2005 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Schizophrenia is associated with language-related dysfunction. A previous study [Schizophr. Res. 59 (2003c) 159] has shown that this abnormality is present at the level of automatic discrimination of change in speech sounds, as revealed by magnetoencephalographic recording of auditory mismatch field in response to across-category change in vowels. Here, we investigated the neuroanatomical substrate for this physiological abnormality. Thirteen patients with schizophrenia and 19 matched control subjects were examined using magnetoencephalography (MEG) and high-resolution magnetic resonance imaging (MRI) to evaluate both mismatch field strengths in response to change between vowel /a/ and /o/, and gray matter volumes of Heschl's gyrus (HG) and planum temporale (PT). The magnetic global field power of mismatch response to change in phonemes showed a bilateral reduction in patients with schizophrenia. The gray matter volume of left planum temporale, but not right planum temporale or bilateral Heschl's gyrus, was significantly smaller in patients with schizophrenia compared with that in control subjects. Furthermore, the phonetic mismatch strength in the left hemisphere was significantly correlated with left planum temporale gray matter volume in patients with schizophrenia only. These results suggest that structural abnormalities of the planum temporale may underlie the functional abnormalities of fundamental language-related processing in schizophrenia.