Spin-lattice Relaxation Research Articles

Disrupted gray matter connectome in vestibular migraine: a combined machine learning and individual-level morphological brain network analysis

BackgroundAlthough gray matter (GM) volume alterations have been extensively documented in previous voxel-based morphometry studies on vestibular migraine (VM), little is known about the impact of this disease on the topological organization of GM morphological networks. This study investigated the altered network patterns of the GM connectome in patients with VM.MethodsIn this study, 55 patients with VM and 57 healthy controls (HCs) underwent structural T1-weighted MRI. GM morphological networks were constructed by estimating interregional similarity in the distributions of regional GM volume based on the Kullback–Leibler divergence measure. Graph-theoretical metrics and interregional morphological connectivity were computed and compared between the two groups. Partial correlation analyses were performed between significant GM connectome features and clinical parameters. Logistic regression (LR), support vector machine (SVM), and random forest (RF) classifiers were used to examine the performance of significant GM connectome features in distinguishing patients with VM from HCs.ResultsCompared with HCs, patients with VM exhibited increased clustering coefficient and local efficiency, as well as reduced nodal degree and nodal efficiency in the left superior temporal gyrus (STG). Furthermore, we identified one connected component with decreased morphological connectivity strength, and the involved regions were mainly located in the STG, temporal pole, prefrontal cortex, supplementary motor area, cingulum, fusiform gyrus, and cerebellum. In the VM group, several connections in the identified connected component were correlated with clinical measures (i.e., symptoms and emotional scales); however, these correlations did not survive multiple comparison corrections. A combination of significant graph- and connectivity-based features allowed single-subject classification of VM versus HC with significant accuracy of 77.68%, 77.68%, and 72.32% for the LR, SVM, and RF models, respectively.ConclusionPatients with VM had aberrant GM connectomes in terms of topological properties and network connections, reflecting potential dizziness, pain, and emotional dysfunctions. The identified features could serve as individualized neuroimaging markers of VM.

Low-field MRI study of the 1H distribution and migration in porous sediments during natural gas conversion from methane hydrate

Gas hydrates, crystalline compounds formed from water and guest molecules like methane, are gaining attention as a promising clean energy source. While research has extensively focused on the extraction and transport of natural gas hydrates from offshore marine sediments, the dynamic processes in the porous sediments remain under explored. This study employs low-field Magnetic Resonance Imaging (MRI) to investigate the in-situ formation and dissociation of methane hydrate within a partially saturated stack of glass beads. By integrating advanced MRI techniques, including 1D dhk SPRITE, bulk T1 distribution, and 2D spatial T2 imaging, this research provides a comprehensive analysis of fluid distribution and migration during phase transitions in the porous sediments. Three key findings emerged from the study. First, SE-SPI measurements successfully quantified hydrate and residual water saturation, aligning with previous X-ray CT and high-field MRI studies and validating low-field MRI for hydrate research. Secondly, this study introduced a volumetric approach to T1 and T2 measurements, distinguishing between free and bound water, with characteristic relaxation times for each, confirming the technique's capability to differentiate types of residual water. Finally, spatially resolved T2 relaxation time distributions revealed vertical fluid migration within the pore spaces, identifying an equilibrium zone where inflow and outflow rates were balanced. Overall, this study underscores the effectiveness of low-field MRI as a noninvasive tool for analyzing hydrate-bearing sediments. The findings lay the groundwork for further exploration of hydrate in porous sediments, enhancing our understanding of gas production dynamics in hydrate-rich environments.

Clustered ultra-small iron oxide nanoparticles as potential T1/T2 dual–modal magnetic resonance imaging contrast agents and application to tumor model

Many studies have been conducted on the use of ultra-small iron oxide nanoparticles (USIONs) (d < 3 nm) as potential positive magnetic resonance imaging (MRI)-contrast agents (CAs); however, there is dearth of research on clustered USIONs. In this study, nearly monodispersed clustered USIONs were synthesized using a simple two-step one-pot polyol method. First, USIONs (d = 2.7 nm) were synthesized, and clustered USIONs (d = 27.9 nm) were subsequently synthesized through multiple cross-linking of USIONs with poly(acrylic acid-co-maleic acid) (PAAMA) polymers with many -COOH groups. The clustered PAAMA-USIONs exhibited very weak ferromagnetism owing to the magnetic interaction between superparamagnetic USIONs; this was evidenced by their appreciable r1= 3.9 s‒1mM‒1and high r2/r1ratio of 14.6. Their ability to function as a dual-modal T1/T2MRI-CA in T1-weighted MRI was demonstrated when they simultaneously exhibited positive and negative contrasts in T1-weighted MRI of tumor model mice after intravenous injection. They displayed positive contrasts at the kidneys, bladder, heart, and aorta and negative contrasts at the liver and tumor.&#xD.

Changes and associations between synovial fluid and magnetic resonance imaging markers of osteoarthritis after high tibial osteotomy

BackgroundMechanobiological mechanisms of osteoarthritis (OA) are unclear. Our objectives were to explore: 1) changes in knee joint physiology using a large panel of synovial fluid biomarkers from before to one year after high tibial osteotomy (HTO) surgery, and 2) the association of changes in the synovial fluid biomarkers with the changes in MRI measures of knee effusion-synovitis and articular cartilage composition.MethodsTwenty-six patients with symptomatic knee OA and varus alignment underwent synovial fluid aspirations and 3 T MRI before and one year after medial opening wedge HTO. Cytokine and growth factor levels in synovial fluid were measured with multiplex assays. Ontology and pathway enrichment was assessed using data protein sets with gene set enrichment analysis (GSEA), and analyzed using linear mixed effects models. MRIs were analyzed for effusion-synovitis and T2 cartilage relaxation time using manual segmentations. Changes in biomarker concentrations were correlated to changes in MRI effusion-synovitis volume and articular cartilage T2 relaxation times.ResultsDecreased enrichment in Toll-like receptor and TNF-α signalling was detected one year after HTO. The leading contributors to this reduction included IL-6, TNF-α and IL-1β, whereas the highest contributors to positive enrichment were EGF, PDGF-BB and FGF-2. Effusion-synovitis volume decreased (mean [95%CI]) one year after HTO (-2811.58 [-5094.40, -528.76mm3]). Effusion-synovitis volume was moderately correlated (r [95% CI]) with decreased MMP-1 (0.44 [0.05; 0.71]), IL-7 (0.41 [0.00; 0.69]) and IL-1β (0.59 [0.25; 0.80]) and increased MIP-1β (0.47 [0.10; 0.73]). Medial tibiofemoral articular cartilage T2 relaxation time decreased (mean [95% CI]) one year after HTO (-0.33 [-2.69; 2.05]ms). Decreased T2 relaxation time was moderately correlated to decreased Flt-3L (0.61 [0.28; 0.81]), IL-10 (0.47 [0.09; 0.73]), IP-10 (0.42; 0.03–0.70) and increased MMP-9 (-0.41 [-0.7; -0.03]) and IL-18 (-0.48 [-0.73; -0.10]).ConclusionsDecreased aberrant knee mechanical loading in patients with OA is associated with decreased biological and imaging measures of inflammation (measured in synovial fluid and on MRI) and increased anabolic processes. These exploratory findings suggest that improvement in knee loading can produce long-term (one year) improvement in joint physiology.

Sex Differences in Fat Distribution and Muscle Fat Infiltration in the Lower Extremity: A Retrospective Diverse-Ethnicity 7T MRI Study in a Research Institute Setting in the USA.

Background: Fat infiltration in skeletal muscle is related to declining muscle strength, whereas excess subcutaneous fat is implicated in the development of metabolic diseases. Methods: Using multi-slice axial T2-weighted (T2w) MR images, this retrospective study characterized muscle fat infiltration (MFI) and fat distribution in the lower extremity of 107 subjects (64M/43F, age 11-79 years) with diverse ethnicities (including White, Black, Latino, and Asian subjects). Results: MRI data analysis shows that MFI, evaluated by the relative intensities of the pixel histogram profile in the calf muscle, tends to increase with both age and BMI. However, statistical significance was found only for the age correlation in women (p < 0.002), and the BMI correlation in men (p = 0.04). Sex disparities were also seen in the fat distribution, which was assessed according to subcutaneous fat thickness (SFT) and the fibula bone marrow cross-sectional area (BMA). SFT tends to decrease with age in men (p < 0.01), whereas SFT tends to increase with BMI only in women (p < 0.01). In contrast, BMA tends to increase with age in women (p < 0.01) and with BMI in men (p = 0.04). Additionally, MFI is positively correlated with BMA but not with SFT, suggesting that compromised bone structure may contribute to fat infiltration in the surrounding skeletal muscle. Conclusions: The findings of this study highlight a sex factor affecting MFI and fat distribution, which may offer valuable insights into effective strategies to prevent and treat MFI in women versus men.

Hypertonic water reabsorption with a parallel-current system via the glandular and saccular renal tubules of the Ruditapes philippinarum.

We investigated the renal function of the brackish water clam, Ruditapes philippinarum, employing magnetic resonance imaging (MRI). This kidney consists of two renal tubules, a glandular (GT) and a saccular (ST) tubule. After exposure to seawater containing manganese ion (Mn2+) at 20℃, the intensity of the T1-weighted MRI and longitudinal relaxation rates (1/T1=R1) of the kidney were increased. In the ST, haemolymph containing Mn2+ entered directly from the auricle, and the Mn2+ concentration ([Mn2+]) increased in the initial part of the ST. Thereafter, [Mn2+] was almost constant until the posterior end of the kidney. The GT received haemolymph from the pedal sinus via the visceral sinus. The GT runs parallel inside the ST, and [Mn2+] increased progressively until it merged with the ST. In a range of seawater with [Mn2+] from 1 to 30 mol·l-1, the [Mn2+] increased 12 fold in the posterior part of the ST, compared to the ambient [Mn2+]. Based on these results, the epithelium of the initial part of the ST reabsorbs water from luminal fluid, building up a higher osmotic pressure. Using this osmotic gradient, hypertonic water is reabsorbed via the epithelium of the GT to the ST, and then transferred to the haemolymph via the epithelium of the ST. Excess water is excreted as urine. This model was supported by the increases in the [Mn2+] in the ST when the clams were exposed to seawater containing Mn2+ at salinity from 26.0 to 36.0‰, showing that the parallel-current system works in hypotonic seawater.

Ultrafast T1-T1ρ NMR for Correlating Different Motional Regimes of Molecules.

Nuclear magnetic resonance (NMR) relaxation times provide detailed information about molecular motions and local chemical environments. Longitudinal T1 relaxation time is most often sensitive to relatively fast, nano- to picosecond ranges of molecular motion. Rotating frame T1ρ relaxation time reflects a much slower, micro- to millisecond range of motion, and the motional regime can be tuned by changing spin-lock field strength. Conventional methods for measuring T1 and T1ρ relaxation times are time-consuming, since experiments must be repeated many times with incremented magnetization recovery or decay delay. In this work, we introduce two novel and efficient NMR methods to correlate the T1 and T1ρ relaxation times. The first method, IR-SPICY, combines the conventional T1 inversion recovery (IR) with the single-scan T1ρ detection-based spin-lock cycle (SPICY). The second method, ultrafast (UF) IR-SPICY, allows measurement of whole two-dimensional T1-T1ρ correlation data in a single scan, in a couple of seconds, based on spatial encoding of the T1 dimension. We demonstrate the performance of the methods by studying relaxation of water in porous silica and hydrogel samples, latter acting as a model of the articular cartilage extracellular matrix. The methods allow correlating different molecular motional regimes, potentially providing unprecedented information about various chemical and biochemical systems, such as structures and fluid dynamics in porous materials, macromolecular changes in tissues, and protein dynamics. One to three orders of magnitude shortened experiment time enable the studies of changing or degrading samples. Furthermore, the single-scan approach may significantly facilitate the use of modern nuclear-spin hyperpolarization techniques to enhance the sensitivity of T1-T1ρ measurements by several orders of magnitude.

AI-ADC: Channel and Spatial Attention-Based Contrastive Learning to Generate ADC Maps from T2W MRI for Prostate Cancer Detection.

Apparent Diffusion Coefficient (ADC) maps in prostate MRI can reveal tumor characteristics, but their accuracy can be compromised by artifacts related with patient motion or rectal gas associated distortions. To address these challenges, we propose a novel approach that utilizes a Generative Adversarial Network to synthesize ADC maps from T2-weighted magnetic resonance images (T2W MRI). By leveraging contrastive learning, our model accurately maps axial T2W MRI to ADC maps within the cropped region of the prostate organ boundary, capturing subtle variations and intricate structural details by learning similar and dissimilar pairs from two imaging modalities. We trained our model on a comprehensive dataset of unpaired T2-weighted images and ADC maps from 506 patients. In evaluating our model, named AI-ADC, we compared it against three state-of-the-art methods: CycleGAN, CUT, and StyTr2. Our model demonstrated a higher mean Structural Similarity Index (SSIM) of 0.863 on a test dataset of 3240 2D MRI slices from 195 patients, compared to values of 0.855, 0.797, and 0.824 for CycleGAN, CUT, and StyTr2, respectively. Similarly, our model achieved a significantly lower Fréchet Inception Distance (FID) value of 31.992, compared to values of 43.458, 179.983, and 58.784 for the other three models, indicating its superior performance in generating ADC maps. Furthermore, we evaluated our model on 147 patients from the publicly available ProstateX dataset, where it demonstrated a higher SSIM of 0.647 and a lower FID of 113.876 compared to the other three models. These results highlight the efficacy of our proposed model in generating ADC maps from T2W MRI, showcasing its potential for enhancing clinical diagnostics and radiological workflows.

Spiral volumetric optoacoustic tomography of reduced oxygen saturation in the spinal cord of M83 mouse model of Parkinson's disease.

Metabolism and bioenergetics in the central nervous system play important roles in the pathophysiology of Parkinson's disease (PD). Here, we employed a multimodal imaging approach to assess oxygenation changes in the spinal cord of the transgenic M83 murine model of PD overexpressing the mutated A53T alpha-synuclein form in comparison with non-transgenic littermates. In vivo spiral volumetric optoacoustic tomography (SVOT) was performed to assess oxygen saturation (sO2) in the spinal cords of M83 mice and non-transgenic littermates. Ex vivo high-field T1-weighted (T1w) magnetic resonance imaging (MRI) at 9.4T was used to assess volumetric alterations in the spinal cord. 3D SVOT analysis and deep learning-based automatic segmentation of T1w MRI data for the mouse spinal cord were developed for quantification. Immunostaining for phosphorylated alpha-synuclein (pS129 α-syn), as well as vascular organization (CD31 and GLUT1), was performed after MRI scan. In vivo SVOT imaging revealed a lower sO2SVOT in the spinal cord of M83 mice compared to non-transgenic littermates at sub-100μm spatial resolution. Ex vivo MRI-assisted by in-house developed deep learning-based automatic segmentation (validated by manual analysis) revealed no volumetric atrophy in the spinal cord of M83 mice compared to non-transgenic littermates at 50μm spatial resolution. The vascular network was not impaired in the spinal cord of M83 mice in the presence of pS129 α-syn accumulation. We developed tools for deep-learning-based analysis for the segmentation of mouse spinal cord structural MRI data, and volumetric analysis of sO2SVOT data. We demonstrated non-invasive high-resolution imaging of reduced sO2SVOT in the absence of volumetric structural changes in the spinal cord of PD M83 mouse model.

A case report: mucinous carcinoma of extrahepatic bile ducts with periportal calcification suggestive of lymphatic calcification.

Mucinous carcinoma is a rare subtype of extrahepatic bile duct (EHBD) cancer in which abundant mucin surrounds cancer cell nests. Calcification is often observed in mucus-producing tumors, and we herein report a case of mucinous carcinoma of EHBD with diffuse periportal calcifications. A 92-year-old woman was seen for jaundice. Non-contrast CT showed diffuse semi-linear branching calcifications extending from the hepatoduodenal ligament along the long axis of the intra- and extrahepatic portal veins. A bile duct mass and multiple lymph nodes were hyperintense on T2-weighted MRI images, and periportal abnormal intensity was visible along the intrahepatic portal tract. On contrast-enhanced CT, the mass and enlarged lymph nodes showed a weak enhancing effect. In addition, a lesion with a similar enhancing effect was observed in parallel with periportal calcification, raising suspicion of tumor extension. An endoscopic bile duct biopsy was performed, which resulted in the tumor being diagnosed as a mucinous carcinoma. Considering the imaging findings, it was determined to be a mucinous carcinoma of EHBD origin, with lymphatic vessel infiltration and multiple lymph node metastases. The lymphatic tracts presented lymphangitic carcinomatosis extending from the hepatoduodenal ligament to intrahepatic portal tracts, and the diffuse periportal calcification was presumed to be calcification associated with the mucin component of tumor infiltration.

Clinical relevance of paramagnetic rim lesion heterogeneity in multiple sclerosis.

Previous studies reveal heterogeneity in terms of paramagnetic rim lesions (PRL) associated tissue damage. We investigated the physiopathology and clinical implications of this heterogeneity. In 103 MS patients (72 relapsing and 31 progressive), brain lesions were manually segmented on 3T 3D-FLAIR and rim visibility was assessed with a visual confidence level score (VCLS) on 3D-EPI phase. Using T1 relaxation time maps, lesions were categorized in long-T1 and short-T1. Lesion age was calculated from time of first gadolinium enhancement (N = 84 lesions). Results on clinical scores were validated in an extended cohort of 167 patients using normalized T1w-MPRAGE lesion values. Rim visibility (VCLS analysis) was associated with increasing lesional T1 (P/PFDR < 0.001). Of 1680 analyzed lesions, 427 were categorized as PRL. Long-T1 PRL were older than short-T1 PRL (average 0.8 vs. 2.0 years, P/PFDR = 0.005/0.008), and featured larger lesional volume (P/PFDR < 0.0001) and multi-shell diffusion-measured axonal damage (P/PFDR < 0.0001). The total volume of long-T1-PRL versus PRL showed 2× predictive power for both higher MS disability (EDSS; P/PFDR = 0.003/0.005 vs. P/PFDR = 0.042/0.057) and severity (MSSS; P/PFDR = 0.0006/0.001 vs. P/PFDR = 0.004/0.007). In random forest, having ≥1 long-T1-PRL versus ≥4 PRL showed 2-4× higher performance to predict a higher EDSS and MSSS. In the validation cohort, long-T1 PRL outperformed (~2×) PRL in predicting both EDSS and MSSS. PRL show substantial heterogeneity in terms of intralesional tissue damage. More destructive, likely older, long-T1 PRL improve the association with MS clinical scales. This PRL heterogeneity characterization was replicated using standard T1w MRI, highlighting its potential for clinical translation.

A Nitric Oxide-Sensing T1 Contrast Agent for In Vivo Molecular MR Imaging of Inflammatory Disease.

Nitric oxide (NO) is a signaling molecule that not only appears in the very early stage of inflammatory disease but also persists in chronic conditions. Its detection in vivo can, therefore, potentially enable early disease detection and treatment monitoring. Due to its transient nature and low abundance, however, noninvasive and deep-tissue imaging of NO dynamics is challenging. In this study, we present a magnetic resonance imaging (MRI) contrast agent based on a manganese porphyrin for specific imaging of NO. This agent is activated by NO, binds to tissue protein, accumulates so long as NO is actively produced, and confers a substantial bright contrast on T1-weighted MRI. In vitro tests confirm the specificity of activation by NO over other reactive oxygen or nitrogen species, absence of inflammation induced by the contrast agent, and sensitivity to NO levels in the tens of micromolar. In vivo demonstration in a mouse model of stress-induced acute myocardial inflammation revealed an over 2.2-times increase in T1 reduction in the inflamed heart compared to a healthy heart. This new NO-activatable T1 contrast agent holds the potential to provide early diagnosis of inflammatory disease, characterize different stages of inflammation, and ultimately guide the design of novel anti-inflammation therapeutics.

Anion and Cation Dynamics in Mixed-Anion Hydroborate Na3(BH4)(B12H12): 1H, 11B, and 23Na NMR Studies

Sodium borohydride-closo-hydroborate Na3(BH4)(B12H12) exhibits high room-temperature ionic conductivity and high electrochemical stability. To study the dynamical properties of this mixed-anion compound at the microscopic level, we have measured the 1H, 11B, and 23Na nuclear magnetic resonance spectra and nuclear spin-lattice relaxation rates over the temperature range of 8–573 K. Our 1H and 11B spin-lattice relaxation measurements have revealed two types of reorientational jump motion. The faster motional process attributed to reorientations of the [BH4]− anions is characterized by an activation energy of 159 meV, and the corresponding reorientational jump rate reaches ~108 s−1 near 130 K. The slower process ascribed to reorientations of the larger [B12H12]− anions is characterized by an activation energy of 319 meV, and the corresponding reorientational jump rate reaches ~108 s−1 near 240 K. The results of the 23Na nuclear magnetic resonance measurements are consistent with the fast long-range diffusion of Na+ ions in Na3(BH4)(B12H12). The diffusive jump rate of Na+ is found to reach ~104 s−1 at 300 K and ~8 × 108 s−1 at 530 K. A comparison of these jump rates with the ionic conductivity data suggests the importance of correlations between diffusing ions.

Superior temporal sulcus folding, functional network connectivity, and autistic-like traits in a non-clinical population.

Autistic-like traits (ALT) are prevalent across the general population and might be linked to some facets of a broader autism spectrum disorder (ASD) phenotype. Recent studies suggest an association of these traits with both genetic and brain structural markers in non-autistic individuals, showing similar spatial location of findings observed in ASD and thus suggesting a potential neurobiological continuum. In this study, we first tested an association of ALTs (assessed with the AQ questionnaire) with cortical complexity, a cortical surface marker of early neurodevelopment, and then the association with disrupted functional connectivity. We analysed structural T1-weighted and resting-state functional MRI scans in 250 psychiatrically healthy individuals without a history of early developmental disorders, in a first step using the CAT12 toolbox for cortical complexity analysis and in a second step we used regional cortical complexity findings to apply the CONN toolbox for seed-based functional connectivity analysis. Our findings show a significant negative correlation of both AQ total and AQ attention switching subscores with left superior temporal sulcus (STS) cortical folding complexity, with the former being significantly correlated with STS to left lateral occipital cortex connectivity, while the latter showed significant positive correlation of STS to left inferior/middle frontal gyrus connectivity (n = 233; all p < 0.05, FWE cluster-level corrected). Additional analyses also revealed a significant correlation of AQ attention to detail subscores with STS to left lateral occipital cortex connectivity. Phenotyping might affect association results (e.g. choice of inventories); in addition, our study was limited to subclinical expressions of autistic-like traits. Our findings provide further evidence for biological correlates of ALT even in the absence of clinical ASD, while establishing a link between structural variation of early developmental origin and functional connectivity.

Sex Disparity in the Canal-to-Body Ratio of the Cervical Spine Indicating the Prevalence of Cervical Myelopathy: A Cross-Sectional Study

Abstract Background A narrow spinal canal and large vertebral body have been thought to be risk factors for cervical myelopathy. It is generally known that males are more likely to develop cervical myelopathy than females. Thus, sex is also a factor that contributes to myelopathy. The anteroposterior (AP) diameter of the cervical spinal canal is well-established as a primary factor of myelopathy. Objective To investigate the sex discrepancy in the canal-to-body ratio of the cervical spine on magnetic resonance imaging (MRI). Materials and Methods This cross-sectional study included 59 males and 59 females, all aged between 20 and 40 years. Morphological parameters, including height, AP diameter of the vertebral body, and AP diameter of the spinal canal, were measured on sagittal T2-weighted MRI cervical spine images for each participant. The canal-to-body ratio, obtained by dividing the spinal canal's AP diameter by the vertebral body's AP diameter, served as a key metric. The average canal-to-body ratio values compared between male and female groups at each spinal level (C3–C7) elucidate potential gender-related differences. Results The height and the AP diameter of the vertebral body were larger in males than in females throughout C3–C7. There was a statistically significant difference between males and females. The AP diameter of the spinal canal was similar for both genders, with no statistically significant difference between them. The mean canal-to-body ratio was significantly larger in females than in males, with a statistically significant difference between males and females at each spinal level. Conclusion Females had a larger canal-to-body ratio, and men had a significantly lower one. The canal-to-body ratio method was thought to be superior to the absolute value of the AP diameter of the spinal canal for the diagnosis of canal stenosis.

Quantitative brain T1 maps derived from T1-weighted MRI acquisitions: a proof-of-concept study.

Longitudinal T1 relaxation time is a key imaging biomarker. In addition, T1 values are modulated by the administration of T1 contrast agents used in patients with tumors and metastases. However, in clinical practice, dedicated T1 mapping sequences are often not included in brain MRI protocols. The aim of this study is to address the absence of dedicated T1 mapping sequences in imaging protocol by deriving T1 maps from standard T1-weighted sequences. A phantom, composed of 144 solutions of paramagnetic agents at different concentrations, was imaged with a three-dimensional (3D) T1-weighed turbo spin-echo (TSE) sequence designed for brain imaging. The relationship between the T1 values and the signal intensities was established using this phantom acquisition. T1 mapping derived from 3D T1-weighted TSE acquisitions in four healthy volunteers and one patient with brain metastases were established and compared to reference T1 mapping technique. The concentration of Gd-based contrast agents in brain metastases were assessed from the derived T1 maps. Based on the phantom acquisition, the relationship between T1 values and signal intensity (SI) was found equal to T1 = 0.35 × SI-1.11 (R2 = 0.97). TSE-derived T1 values measured in white matter and gray matter in healthy volunteers were equal to 0.997 ± 0.096 s and 1.358 ± 0.056 s (mean ± standard deviation), respectively. Mean Gd3+ concentration value in brain metastases was 94.7 ± 30.0 μM. The in vivo results support the relevance of the phantom-based approach: brain T1 maps can be derived from T1-weighted acquisitions. High-resolution brain T1 maps can be generated, and contrast agent concentration can be quantified and imaged in brain metastases using routine 3D T1-weighted TSE acquisitions. Quantitative T1 mapping adds significant value to MRI diagnostics. T1 measurement sequences are rarely included in routine protocols. T1 mapping and concentration of contrast agents can be derived from routine standard scans. The diagnostic value of MRI can be improved without additional scan time.

MRI-Based Multi-Class Relevance Vector Machine Classification of Neurodegenerative Diseases.

Machine learning algorithms are a promising automated candidate that can help mitigate the growing need for dementia experts. Despite the substantial development in MRI-based machine learning analyses, case misclassification is a universal finding, yet the reasons behind misclassification are poorly understood. We implemented a multi-class classification approach that uses relevance vector machine and logistic classification to classify research participants based on their whole-brain T1-weighted MRI scans. A total of 468 participants from seven diagnostic classes were included: 144 healthy controls, 84 Alzheimer's disease, 108 behavioral variant frontotemporal dementia (bvFTD), 30 semantic variant primary progressive aphasia (svPPA), 30 non-fluent variant primary progressive aphasia (nfvPPA), 30 corticobasal syndrome (CBS), and 42 progressive supranuclear palsy syndrome (PSPS). We compared the algorithm's diagnostic accuracy against the clinical, pathological, genetic, and quantitative imaging data. The exact neurodegenerative syndrome was predicted in 71% of the cases, the neurodegenerative disease spectrum was predicted in 80% of the cases, and the algorithm distinguished controls from any dementia in 85% of the cases. The algorithm showed high performance in diagnosing healthy controls, moderate performance in diagnosing AD, bvFTD, and svPPA, and low performance in diagnosing CBS, nfvPPA, and PSPS. Based on the quantitative imaging data, most of the misclassified neurodegenerative cases had minimal atrophy and brain volumes comparable to healthy controls. In AD, early-onset AD cases with minimal brain atrophy represented most of the misclassified cases. In bvFTD, FTD genetic mutation carriers (predominantly C9orf72 repeat expansion), FTD phenocopy, patients meeting only possible bvFTD criteria represented most misclassified cases. Case misclassification in machine learning studies in neurodegenerative diseases results from neurodegenerative disease heterogeneity and the limitations of structural MRI's ability to capture the whole gamut of biological changes. Larger and more inclusive datasets that are representative of population biologic heterogeneity are needed to train better machine learning techniques, and a margin of error is expected and should be acceptable, like the uncertainty of a clinical diagnosis by a dementia expert.

Impact of Surgical Revascularization on Regression of Enlarged Perivascular Spaces in Adult Moyamoya Disease.

Previous studies have suggested that enlarged perivascular spaces (EPVSs) are potential radiological markers of cerebral ischemia in moyamoya disease (MMD). However, serial changes in EPVSs after surgical revascularization have not yet been clarified. We aimed to elucidate the postoperative changes in EPVSs in adult patients with MMD, clinical and radiological factors affecting the number of EPVSs, and the degree of postoperative changes. We counted the EPVSs in the centrum semiovale in each hemisphere on a T2-weighted MRI performed before surgery. EPVSs were quantified 3months and 2years after combined bypass surgery in surgically treated patients and compared with the number of EPVSs before surgery. We performed multivariate logistic regression analysis to identify the clinical and radiological factors associated with the number of EPVSs. This study included 120 hemispheres of 65 adults with MMD. Older age (P < 0.01), posterior cerebral artery (PCA) involvement (P < 0.01), and cerebral blood flow (CBF) impairment (P = 0.02) were significantly associated with a large number of EPVSs. The number of EPVSs markedly decreased at 3months and 2years after surgery compared with that before surgery (P < 0.01). PCA involvement (P = 0.04) and CBF impairment (P = 0.02) were independent predictors of the regression of EPVSs after surgery. The number of EPVSs in the centrum semiovale was closely associated with age, PCA involvement, and CBF impairment in adult patients with MMD, which remarkably regressed after surgical revascularization, especially in the hemispheres with PCA involvement and CBF impairment. EPVSs are reversible radiological markers reflecting impaired cerebral hemodynamics in adult patients with MMD.

T2 MRI visible Perivascular Spaces in Parkinson`s Disease: clinical significance and association with polysomnography measured sleep.

Poor sleep quality might contribute to the risk and progression of neurodegenerative disorders via deficient cerebral waste clearance functions during sleep. In this retrospective cross-sectional study, we explore the link between enlarged perivascular spaces (PVS), a putative marker of sleep-dependent glymphatic clearance, with sleep quality and motor symptoms in Parkinson`s disease (PD) patients. T2-weighted MRI images of 20 patients and 17 healthy control subjects were estimated visually for PVS in the basal ganglia (BG) and centrum semiovale (CSO). The patient group additionally underwent a single-night polysomnography. Readouts included polsyomnographic sleep features and slow-wave activity (SWA), a quantitative EEG marker of sleep depth. Associations between PVS counts, PD symptoms (MDS-UPDRS scores) and sleep parameters were evaluated using correlation and regression analyses. Intra- and inter-rater reproducibility was assessed with weighted Cohen`s kappa coefficient. BG and CSO PVS counts in both patients and controls did not differ significantly between groups. In patients, PVS in both brain regions were negatively associated with SWA (1-2Hz) (BG: r(15)=-0.58, padj=0.015 and CSO: r(15)=-0.6, padj=0.015). Basal ganglia PVS counts were positively associated with motor symptoms of daily living (IRR=1.05, CI [1.01, 1.09], p=0.007, padj=0.026) and antidepressant use (IRR=1.37, CI [1.05, 1.80], p=0.021, padj=0.043) after controlling for age. Centrum Semiovale PVS counts in patients were positively associated with a diagnosis of REM sleep behaviour disorder (IRR=1.39, CI [1.06 , 1.84]), p=0.018, padj=0.11). These results add evidence that sleep deterioration may play a role in impairing glymphatic clearance via altered perivascular function, potentially contributing to disease severity in PD patients.

A simplified approach to define cervical vertebral levels in spinal cord MRI studies.

Spinal cord (SC) cross-sectional areas (CSAs) assessed with MRI have proven to be extremely valuable imaging markers in several diseases. Among the challenges is the delineation of vertebral levels to determine level-dependent changes in cord atrophy. With this study, we aimed to (1) test the hypothesis that there is proportionality in the position of the first six intervertebral discs and the length of the upper portion of the SC and (2) show that a proportionality approach can simplify the CSA assessment across vertebrae offering good reliability. Forty-six volunteers underwent standard T2-weighted and T1-weighted cervical SC MRI acquisitions. The distance between the obex and the intervertebral discs (from C2-C3 to T1-T2) was measured on the T2-weighted acquisitions of the entire cohort. In a test-retest experiment on 12 subjects, the % disc position values were used to define vertebral levels, and a comparison was performed with manual vertebrae assignment in terms of mean CSA and its coefficient of variation. The mean upper cord length for the cohort was 144.0±13.1mm. The discs' level % position in the upper cord was found to be fairly consistent, with standard deviations of 0.8%-1.7%. The mean vertebral CSA obtained with the proportionality method was substantially equivalent to the manual approach in terms of mean CSA values and test-retest reliability. With this study, we propose a proportionality method for the assignment of cervical SC vertebral levels that can simplify the processing of MRI datasets in the context of CSA measurements.