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We measure spectra of water mobilities (i.e., mean diffusivities) from intravoxel pools in brain tissues of healthy subjects with a non-parametric approach. Using a single-shot isotropic diffusion encoding (IDE) preparation, we eliminate signal confounds caused by anisotropic diffusion, including microscopic anisotropy, and acquire in vivo diffusion-weighted images (DWIs) over a wide range of diffusion sensitizations. We analyze the measured IDE signal decays using a regularized inverse laplace transform (ILT) to derive a probability distribution of mean diffusivities of tissue water in each voxel. Based on numerical simulations we assess the sensitivity and accuracy of our ILT analysis and optimize an experimental protocol for use with clinical MRI scanners. In vivo spectra of intravoxel mean diffusivities measured in healthy subjects generally show single-peak distributions throughout the brain parenchyma, with small differences in peak location and shape among white matter, cortical and subcortical gray matter, and cerebrospinal fluid. Mean diffusivity distributions (MDDs) with multiple peaks are observed primarily in voxels at tissue interfaces and are likely due to partial volume contributions. To quantify tissue-specific MDDs with improved statistical power, we average voxel-wise normalized MDDs in corresponding regions-of-interest (ROIs). This non-parametric, rotation-invariant assessment of isotropic diffusivities of tissue water may reflect important microstructural information, such as cell packing and cell size, and active physiological processes, such as water transport and exchange, which may enhance biological specificity in the clinical diagnosis and characterization of ischemic stroke, cancer, neuroinflammation, and neurodegenerative disorders and diseases. •We optimize a clinical protocol to measure isotropic diffusion encoded brain images.•We derive rotation-invariant distributions of intravoxel mean diffusivities in vivo.•We assess the uncertainty of measuring intravoxel mean diffusivity distributions.•Mean diffusivities distributions show mostly single peaks in healthy brain voxels.

Diffusion tensor imaging (DTI) is essential for assessing brain microstructure but requires long acquisition times, limiting clinical use. Recent deep learning (DL) approaches, such as SuperDTI or deepDTI, improve DTI metrics but demand large, high-quality datasets for training. We propose a self-supervised deep learning with fine-tuning (SSDLFT) framework to reduce training data requirements. SSDLFT involves self-supervised pretraining, which denoises data without clean labels, followed by fine-tuning with limited high-quality data. Experiments using Human Connectome Project data show that SSDLFT outperforms traditional methods and other DL approaches in qualitative and quantitative assessments of DWI reconstructions and tensor metrics. SSDLFT’s ability to maintain high performance with fewer training subjects and DWIs presents a significant advancement, enhancing DTI’s practical applications in clinical and research settings.

We evaluated white matter microstructure integrity in perinatally HIV-infected (PHIV) youths receiving cART compared to age- and gender-matched healthy youths through DTI metrics using voxel-based morphometry (VBM). We investigated 14 perinatally HIV-infected patients (age 17.9 ± 2.5 years) on cART and 17 healthy youths (HC) (age 18.0 ± 3.0 years) using a 3T MRI scanner. Four DTI-derived metrics were fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). Statistical analysis was done with voxel-based analysis of covariance (ANCOVA), with age and gender as covariates. Region-of-interest secondary analyses in statistically significant regions were also performed. Regional increases in FA in the PHIV youths were found in left middle frontal gyrus, right precuneus, right lingual gyrus, and left supramarginal gyrus. Increased MD was found in the right precentral gyrus while decreased MD was found in the white matter of the right superior parietal lobule and right inferior temporal gyrus/fusiform gyrus. Regions of increased/decreased RD overlapped with regions of increased/decreased MD. Both increased and decreased AD were found in three to four regions respectively. The regional FA, MD, RD, and AD values were consistent with the voxel-based analysis findings. The findings are mostly consistent with previous literature, but increased FA has not been previously reported for perinatally HIV-infected youths. Potentially early and prolonged therapy in our population may have contributed to this new finding. Both toxicity of antiretroviral therapy and indolent infection must be considered as causative factors in the DTI metric changes that we have observed.

Background: Hemisensory syndrome is characterized by a nondermatomal sensory deficit involving one half of the body. With the conventional imaging techniques, researches find low diagnostic yield in this condition; however, with the advancements in MRI imaging, there is hope to find the pathophysiological basis of hemisensory symptoms. Objective: To evaluate microstructural and perfusion changes in brain parenchyma in patients with hemisensory syndrome on MRI with diffusion tensor imaging (DTI) and arterial spin labeling (ASL). Material and Methods: A total of 20 patients with hemisensory symptoms and 10 age-matched controls were enrolled and divided in two study groups - a) case vs. control and b) affected vs. nonaffected cerebral hemisphere in cases. Quantification of absolute cerebral blood flow (aCBF), fractional anisotropy (FA), and mean diffusivity (MD) was done in both groups. Results: On ASL, there was significantly increased aCBF in thalamus on the contralateral-affected side. DTI revealed significantly decreased FA in the thalamus and increased FA in corona radiata of the affected side. There was a significant difference for MD of corona radiata between affected and nonaffected hemisphere. The mean value of MD in corona radiata is decreased on the affected side. Conclusion: Changes in advanced neuroimaging techniques like ASL and DTI along the pain processing pathway suggest an alteration in neuronal density and activity at the microstructural level. These findings may provide an insight into the etiopathogenesis of pain syndromes.

Background Bipolar disorder (BD) is one of the most debilitating and recurrent mental illnesses globally. It is characterised by frequent mood swings, both high and low, and the behavioural, motivational, and cognitive changes that go along with them. In recent years, studies using diffusion tensor imaging (DTI) have brought attention to the crucial part white matter (WM) abnormalities play in BD. The aim of this study was to evaluate white matter integrity using DTI in children with Type I BD, comparing findings with a healthy control group. Results Children with Type I BD exhibited significantly lower FA values across multiple white matter tracts, including the anterior and posterior corona radiata (ACR,PCR), superior and inferior longitudinal fasciculi (SLF,ILF), cingulum (CING), anterior thalamic radiation (ATR), fornix, corpus callosum (CC), and internal capsule (PLIC,ALIC) (P < 0.001). The bipolar group also showed greater mean diffusivity than healthy individuals; statistically significant differences at ACR, PCR, SCR, SLF, ILF, CING, ATR, fornix, CC, ALIC and PLIC; (P value < 0.001). Additionally, the patient group's Radial Diffusivity (RD) was noticeably higher than the control group's at ACR, PCR, SCR, SLF, ILF, CING, ATR, fornix and CC (P value < 0.001), and was insignificantly different at ALIC and PLIC.Apparent Diffusion Coefficient (ADC) was significantly higher at patient group, this difference reached statistical significance in the ACR, PCR, SLF, ATR, CC, ALIC, and PLIC (P value < 0.05) and was insignificantly different at ILF, CING, SCR, fornix and PCR between both groups. Conclusion Combining FA, MD, and RD parameters provided a comprehensive assessment of microstructural white matter changes in pediatric Type I BD, demonstrating DTI's potential as a diagnostic tool.

This study aimed to investigate possible signal changes in the dentate nucleus (DN) on diffusion tensor imaging (DTI) after administration of gadobutrol in a pediatric cohort. Total of 50 pediatric patients (mean age: 6.2 ± 4.3 years) with normal renal function exposed exclusively to the macrocyclic GBCA (mcGBCA) gadobutrol and 50 age- and sex-matched control patients with nonpathological neuroimaging findings (and no GBCA administration). Mean diffusivity (MD) and fractional anisotropy (FA) values were determined in the DN. A paired t test was performed to compare FA, MD values, and DN-to-middle cerebral peduncle (MCP) T1WI SI ratios between children exposed to gadobutrol and controls. Pearson correlation analysis was conducted to determine any correlation between FA and MD values as well as T1WI SI ratios and confounding parameters. The mean FA values of DN was significantly lower in children with mcGBCA than in the control group (p < 0.001; non-GBCA group, 0.299 ± 0.03; mcGBCA group, 0.254 ± 0.05), but no significant difference of the T1WI SI ratio was noted between the mcGBCA group (0.946 ± 0.06) and the control group (0.963 ± 0.05; p = 0.336). There was also a significant MD value difference between mcGBCA group and control group (p < 0.001; non-GBCA group, 0.152 ± 0.02 × 10−3 mm2/s; mcGBCA group, 0.173 ± 0.03 × 10−3 mm2/s). A significant correlation was identified between FA/MD values and the number of mcGBCA administration (FA; correlation coefficient =  − 0.355, p = 0.011 and MD; correlation coefficient = 0.334, p = 0.018). The administration of the gadobutrol was associated with higher MD and lower FA values in DN suggesting a difference in cerebellar tissue integrity between children exposed to mcGBCAs and control group.

A noninvasive technique for assessing tumor tissue characteristics is required to assist preoperative surgical planning for malignant brain tumors. Preoperative information on tumor cell density within a tumor would help better define the target for tumor biopsy, resulting in more accurate diagnosis and grading of malignant brain tumors. One possible source of this information is diffusion tensor imaging (DTI), although to date studies have focused on its ability to delineate white matter fiber tracks by fiber-tracking and to detect tumor infiltration around the tumor and normal white matter interface. However, the use of DTI for providing information on cell density has also been examined, although with the controversial results. In addition the exact relationships between cell density and the two key values that DTI provides, namely fractional anisotropy (FA) and mean diffusivity (MD), still need to be investigated. In the present study we performed a retrospective investigation of tumor cell density and FA and MD values in biopsy cases. We found that FA has a good positive correlation ( R = 0.75) and MD has a good negative correlation ( R = 0.70) with tumor cell density within the tumor core. Similar correlation was observed between the Ki-67 labeling index and FA ( R = 0.71) and MD ( R = 0.62). Thus, measurement of both FA and MD within the tumor core has a potential to provide detailed information on tumor cell density within the tumor. Although data obtained from DTI should be interpreted carefully and comprehensively with other imaging modalities such as positron emission tomography, DTI seems to be informative for planning the best biopsy target containing the highest cell density.

The aim of this study was to investigate the fractional anisotropy (FA) and mean diffusivity (MD) using a diffusion tensor imaging technique and whole-brain voxel-based analysis in patients with comitant strabismus. A total of 19 (nine males and ten females) patients with comitant strabismus and 19 age-, sex-, and education-matched healthy controls (HCs) underwent magnetic resonance imaging examination. Imaging data were analyzed using two-sample t-tests to identify group differences in FA and MD values. Patients with comitant strabismus were distinguishable from HCs by receiver operating characteristic curves. Compared with HCs, patients with comitant strabismus exhibited significantly decreased FA values in the brain regions of the left superior temporal gyrus and increased values in the bilateral medial frontal gyrus, right globus pallidus/brainstem, and bilateral precuneus. Meanwhile, MD value was significantly reduced in the brain regions of the bilateral cerebellum posterior lobe and left middle frontal gyrus but increased in the brain regions of the right middle frontal gyrus and left anterior cingulate. These results suggest significant brain abnormalities in comitant strabismus, which may underlie the pathologic mechanisms of fusion defects and ocular motility disorders in patients with comitant strabismus.

Schizophrenia is a chronic disabling mental illness. A novel magnetic resonance imaging (MRI) technique known as diffusion tensor imaging (DTI) is a non-invasive and does not need external contrast materials. It is capable of identifying anomalies in the white matter micro-structure of the brain. This work conducted the DTI in schizophrenic patients to evaluate altered structural integrity in grey and white matter. This prospective case control study was conducted on 25 schizophrenic patients selected from neuropsychiatric department, and 25 age/sex-matched healthy controls. Schizophrenic patients showed diminished fractional anisotropy in fornix, corpus callosum, right cingulum, right superior and inferior occipito-frontal fasciculi. Increased mean diffusivity in right inferior occipito-frontal fasciculus, corpus callosum, right thalamus and right basal ganglia were noted in schizophrenic patients. Fractional anisotropy and mean diffusivity had a predictive value for detection of schizophrenic patients. DTI of white and grey matter tracts is considered a promising tool for diagnosis of schizophrenic patients which usually have prolonged illness, chronic course and poor outcome.

Aim of study To evaluate the role of diffuse tensor imaging (DTI) in detecting structural alterations following TBI with persistent symptoms without findings on conventional structural imaging. Methods This was a prospective study that enrolled a total of 30 individuals (12 females and 18 males), 6 control with no history of trauma and 24 with previous history of trauma. All subjects underwent conventional brain MRI and DTI. The eigenvalues of the genue and splenium of corpus callosum (CC), superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF), corticospinal tract (CS), arcuate fasciculus (AF) were measured bilaterally in all cases using suitable region of interest and the fraction anisotropy (FA), mean diffusivity (MD), were calculated. FA and MD values were compared between patients and control subjects. Diagnostic accuracy was calculated for FA, MD and combined. Sensitivity and Specificity were determined from the curve and PPV, NPV and accuracy underwent calculation through cross-tabulation. Result As compared with controls, FA was significantly decreased and MD was significantly increased in genue and splenium of CC and CS. For the Combined FA & MD in differentiating cases with trauma there was statistically significant difference in SLF, AF, genue, splenium, ILF and CS as p value < 0.05. Conclusions DTI parameters is a promising tool in the detection of subtle brain parenchymal changes in patients with TBI who have persistent symptoms and no evident abnormalities on conventional MRI. Furthermore combined use of FA and MD shows better diagnostic accuracy in differentiation between control and trauma patient.