Magnetic Resonance Diffusion Tensor Imaging Research Articles

Reorganization of the structural connectome during vision recovery in pituitary adenoma patients post-transsphenoidal surgery.

Pituitary adenomas (PAs) can exert pressure on the optic apparatus, leading to visual impairment. A subset of patients may observe a swift improvement in their vision following surgery. Nevertheless, the alterations in the structural connectome during the early postoperative period remain largely unexplored. The research employed probabilistic tractography, graph theoretical analysis, and statistical methods on preoperative and postoperative structural magnetic resonance imaging and diffusion tensor images from 13 PA patients. Postoperative analysis revealed an increase in global and local efficiency, signifying improved network capacity for parallel information transfer and fault tolerance, respectively. Enhanced clustering coefficient and reduced shortest path length were also observed, suggesting a more regular network organization and shortened communication steps within the brain network. Furthermore, alterations in node graphical properties were detected, implying a restructuring of the network's control points, possibly contributing to more efficient visual processing. These findings propose that rapid vision recovery post-surgery may be associated with significant reorganization of the brain's structural connectome, enhancing the efficiency and adaptability of the network, thereby facilitating improved visual processing.

Evaluation of Magnetic Resonance Diffusion Tensor Imaging in Early Detection of Cervical Spondylotic Myelopathy

Evaluation of Magnetic Resonance Diffusion Tensor Imaging in Early Detection of Cervical Spondylotic Myelopathy

Structure of brain grey and white matter in infants with spastic cerebral palsy and periventricular white matter injury.

To investigate the possible covariation of grey matter volume (GMV) and white matter fractional anisotropy in infants with spastic cerebral palsy (CP) and periventricular white matter injury. Thirty-nine infants with spastic CP and 25 typically developing controls underwent structural magnetic resonance imaging and diffusion tensor imaging. Multimodal canonical correlation analysis with joint independent component analysis were used to capture differences in GMV and fractional anisotropy between groups. Correlation analysis was performed between imaging findings and clinical features. Infants with spastic CP showed one joint group-discriminating component (i.e. GMV-fractional anisotropy) associated with regions in the cortico-basal ganglia-thalamo-cortical loop and in the corpus callosum compared to typically developing controls and one modality-specific group-discriminating component (i.e. GMV). Significant negative correlations were found between loadings in certain regions and the motor function score in spastic CP. In infants with spastic CP, covarying GMV-fractional anisotropy and altered GMV in specific regions were implicated in motor dysfunction, which confirmed that simultaneous GMV and fractional anisotropy changes underly motor deficits, but might also extend to sensory, cognitive, or visual dysfunction. These findings also suggest that multimodal fusion analysis allows for a more comprehensive understanding of the relevance between grey and white matter structures and its crucial role in the neuropathological mechanisms of spastic CP.

Role of magnetic resonance diffusion tensor imaging in assessment of back muscles in young adults with chronic low back pain

BackgroundLow back pain (LBP) is one of the most common musculoskeletal complaints and considered as the most disabling condition among general population. Magnetic resonance imaging (MRI) is the preferred modality in imaging of LBP. Diffusion tensor imaging (DTI) is a version of MRI that can detect tissue microstructure changes occurring in different pathologies. The commonly used parameters are fractional anisotropy (FA) and mean diffusivity (MD). We aimed in this study to evaluate the role of DTI in the assessment of back muscles in young adults with chronic LBP with no major neurological or orthopedic disorders.ResultsThere was a statistically significant difference in MD values of back muscles between patients and control groups. At the ROC curve, for psoas muscle, the AUC was 0.906 with a cutoff point of 0.951. Sensitivity and specificity were 89.2% and 90.9% with accuracy 89.8%. For multifidus muscle, the AUC was 0.919 with a cutoff point of 1.29. Sensitivity and specificity were 91.9% and 90.9% with accuracy 91.4%. For erector spinae muscle, the AUC was 0.834 with a cutoff point of 1.224. Sensitivity and specificity were 81.1% and 72.7% with accuracy 77.9%. There was a statistically significant difference in FA values of back muscles between the patients and control groups. At the ROC curve, for psoas muscle, the AUC was 0.840 with a cutoff point of 0.546. Sensitivity and specificity were 81.1% and 72.7% with accuracy 77.97%. For multifidus muscle, the AUC was 0.875 with a cutoff point of 0.415. Sensitivity and specificity were 81.1% and 90.9% with accuracy 84.7%. For erector spinae muscle, the AUC was 0.805 with a cutoff point of 0.437. Sensitivity and specificity were 81.1% and 77.3% with accuracy 79.7%.ConclusionsDTI is a valuable promising noninvasive tool in the assessment of back muscles quality in patient with chronic low back pain, with no detected neurological or orthopedic pathologies. This is due to its sensitivity to microscopic intracellular changes that could not be detected on conventional imaging, allowing better tissue characterization.

Thalamopeduncular Tumors in Pediatric Age: Advanced Preoperative Imaging to Define Safe Surgical Planning: A Multicentric Experience.

Background: Thalamopeduncular tumors are challenging lesions arising at the junction between the thalamus and the cerebral peduncle. They represent 1-5% of pediatric brain tumors, are mainly pilocytic astrocytoma and occur within the first two decades of life. To date, the optimal treatment remains unclear. Methods: We retrospectively reviewed pediatric patients who underwent surgery for thalamopeduncular tumors in the Academic Pediatric Neurosurgery Unit of Padova and Verona from 2005 to 2022. We collected information on age, sex, symptoms, preoperative and postoperative neuroradiological studies, histological specimens, surgical approaches, and follow-up. Results: We identified eight patients with a mean age of 9 years. All lesions were pilocytic astrocytoma. The main symptoms were spastic hemiparesis, cranial nerve palsy, headache, and ataxia. The corticospinal tract was studied in all patients using diffusion-tensor imaging brain MRI and in two patients using navigated transcranial magnetic stimulation. The transsylvian approach was the most frequently used. A gross total resection was achieved in two patients, a subtotal resection in five and a partial resection in one. In three patients, a second treatment was performed due to the regrowth of the tumor, performing an additional surgery in two cases and a second-look surgery followed by adjuvant therapy in one. After the surgery, four patients maintained stability in their postoperative neurological exam, two patients improved, and two worsened but in one of them, an improvement during recovery occurred. At the last follow-up available, three patients were disease-free, four had a stable tumor residual, and only one patient died from the progression of the disease. Conclusions: Advanced preoperative tools allow one to define a safe surgical strategy. Due to the indolent behavior of thalamopeduncular tumors, surgery should be encouraged.

Role of MRI Diffusion Tensor Imaging in Early Diagnosis of Cervical Spondylotic Myelopathy (CSM)

Abstract Background and Purpose Cervical spondylotic myelopathy (CSM) is a common degenerative disorder of the cervical spine and is considered as the most common cause of spinal cord dysfunction in older individuals worldwide. Assessing the severity of the disease objectively remains a challenge and there is still remaining controversy in terms of the optimal timing and indications for surgical intervention. The conventional MRI is the gold standard for radiographic evaluation of the spinal cord; however, it cannot assess the underlying microstructural deficits of the spinal cord and it has a limited application in determining prognosis and recovery of the disease [1]. We sought to assess the utility of MR diffusion tensor imaging as an imaging technique in clinically suggested CSM patients by obtaining the microstructural parameters (Fractional anisotropy; FA and apparent diffusion coefficient; ADC) in the cervical spinal cord segments. Patient & methods our study was a prospective cross-sectional study including 40 patients with clinical manifestations of cervical spondylotic myelopathy. The patients were sorted according to the European myelopathy score into three categories as follows: grade 1 (with mild symptoms), grade 2 (with moderate symptoms) and grade 3 (with severe symptoms). All the patients were investigated with a 1.5 T MRI unit acquiring conventional MRI and DTI sequences. FA and ADC values at each spinal segment from C2/C3 to C6/C7 were generated and measured using manual drawing of multiple ROIs within the cervical cord in the sagittal and axial combined anatomical and color-coded images. For each of these cases, the patient’s age, gender, DTI parameters at each spinal segment level, maximum compression level, conventional T2WI characteristics and EMS score were recorded, analyzed and compared. Results The study included 23 females (57.5%) and 17 males (42.5%). Their age ranged from 30 to 72 years with a mean age of 47.3 ± 9.79 years. The study revealed a significant difference in the mean FA and ADC values between stenotic and non-stenotic segments of the cervical spinal cord. There was a significant correlation between the European myelopathy score and DTI parameters (FA and ADC). FA and ADC values performed better in recognizing myelopathic changes in patients who were classified as grade 1 according to EMS compared to conventional MRI T2WI which performed very poorly in recognizing myelopathy changes in the same patients, therefore DTI indices were more sensitive in the detection of CSM patients compared to conventional MRI especially in early myelopathic stages. T2 weighted images were highly significant in recognizing myelopathy changes in patients who were classified as grade 3 according to EMS. The CSM patients had significant FA decrease and ADC increase at the most compressed part of the cervical spinal cord and there was a significant correlation between the number of patients who had myelopathic changes by DTI parameters and the severity of disease. The FA sensitivity and specificity in recognition of myelopathic changes were 73.5% and 83.3% respectively and the ADC sensitivity and specificity were 100% and 70.6% respectively. Conclusion In conclusion, diffusion tensor imaging enhances the efficacy and accuracy of MRI in the diagnosis of cervical spondylotic myelopathy. Therefore, it can be used as a non-invasive modality for detection of the spondylotic myelopathy changes in the early stages helping to decide the appropriate timing of decompression surgery before attaining the irreversible chronic changes. Abbreviations ADC: Apparent diffusion coefficient; CSM: Cervical spondylotic myelopathy; DTI: Diffusion tensor imaging; FA: Fractional Anisotropy; EMS: European myelopathy score

Potential Role of MR Diffusion Tensor Imaging of the Spinal Cord in Early Detection of Cervical Spondylotic Myelopathy and Assessment of Its Severity

Background Cervical spondylotic myelopathy is the most common cause of spinal dysfunction in adults. Recent studies have shown a potential role for diffusion tensor imaging as a novel method for early detection of cervical cord myelopathy as compared with conventional MR sequences. Aim of the Work To evaluate the role of MR diffusion tensor imaging in the early detection of cervical spondylotic myelopathic changes in comparison to conventional MRI sequences to determine best clinical management and outcome for the patients. Patients and Methods Our study is a prospective study that included patients from August 2021 to December 2021. The study included 20 patients with clinical symptoms of cervical spondylotic myelopathy, referred to the Radiology department, Ain Shams University Hospitals for MRI cervical study. Results Our results showed a highly significant reduction of FA values and highly significant increase of ADC values of the cord opposite to the level of the most affected disc (P value <0.001 and 0.002 respectively). We also found that the magnitude of FA reduction and ADC increase correlated positively with the severity of disc affection, with the highest drop in FA values and increase in ADC values found to be in patients with established spinal cord hyperintensity on T2WI. Conclusion Diffusion tensor imaging could be used in early detection of cervical cord myelopathy before the appearance of altered cord intensity on conventional MRI sequences and in assessment of its severity.

White matter hyperintensities in migraine are not mediated by a dysfunction of the glymphatic system-A diffusion tensor imaging magnetic resonance imaging study.

We assessed whether brain magnetic resonance imaging (MRI) markers of glymphatic function are altered in patients with migraine and brain white matter hyperintensities (WMHs). The glymphatic system is responsible for the outflow of waste products from the brain. An impaired glymphatic system has been associated with WMH; however, this impairment has not been shown in patients with migraine. The present cross-sectional study included consecutive patients with migraine from a single tertiary headache center. Glymphatic function was assessed by measuring the diffusion tensor imaging along the perivascular space (DTI-ALPS) technique, resulting in an index value. WMHs were assessed and quantified by using the Scheltens semi-quantitative score. We included 147 patients (120 women [81.6%]) with a median (interquartile range [IQR]) age of 45 (36-50) years. In all, 74 (50.3%) patients had WMHs. The median (IQR) ALPS index was similar in patients with WMHs compared with those without, at 2.658 (2.332-3.199) versus 2.563 (2.222-3.050) (p = 0.344). The Scheltens score did not correlate with ALPS index (rho = 0.112, p = 0.268). Our results suggest that the presence of WMHs is not associated with an impairment in the glymphatic system in patients with migraine. Although negative and worthy of further confirmation, our finding has implications for the understanding of the nature of WMH in patients with migraine.

Probing Evidence of Cerebral White Matter Microstructural Disruptions in Ischemic Heart Disease Before and Following Cardiac Rehabilitation: A Diffusion Tensor MR Imaging Study.

Ischemic heart disease (IHD) is linked to brain white matter (WM) breakdown but how age or disease effects WM integrity, and whether it is reversible using cardiac rehabilitation (CR), remains unclear. To assess the effects of brain aging, cardiovascular disease, and CR on WM microstructure in brains of IHD patients following a cardiac event. Retrospective. Thirty-five IHD patients (9 females; mean age = 59 ± 8 years), 21 age-matched healthy controls (10 females; mean age = 59 ± 8 years), and 25 younger controls (14 females; mean age = 26 ± 4 years). 3 T diffusion-weighted imaging with single-shot echo planar imaging acquired at 3 months and 9 months post-cardiac event. Tract-based spatial statistics (TBSS) and tractometry were used to compare fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) in cerebral WM between: 1) older and younger controls to distinguish age-related from disease-related WM changes; 2) IHD patients at baseline (pre-CR) and age-matched controls to investigate if cardiovascular disease exacerbates age-related WM changes; and 3) IHD patients pre-CR and post-CR to investigate the neuroplastic effect of CR on WM microstructure. Two-sample unpaired t-test (age: older vs. younger controls; IHD: IHD pre-CR vs. age-matched controls). One-sample paired t-test (CR: IHD pre- vs. post-CR). Statistical threshold: P < 0.05 (FWE-corrected). TBSS and tractometry revealed widespread WM changes in older controls compared to younger controls while WM clusters of decreased FA in the fornix and increased MD in body of corpus callosum were observed in IHD patients pre-CR compared to age-matched controls. Robust WM improvements (increased FA, increased AD) were observed in IHD patients post-CR. In IHD, both brain aging and cardiovascular disease may contribute to WM disruptions. IHD-related WM disruptions may be favorably modified by CR. 3 TECHNICAL EFFICACY: Stage 2.

Hypertensive Adults Exhibit Lower Myelin Content: A Multicomponent Relaxometry and Diffusion Magnetic Resonance Imaging Study.

It is unknown whether hypertension plays any role in cerebral myelination. To fill this knowledge gap, we studied 90 cognitively unimpaired adults, age range 40 to 94 years, who are participants in the Baltimore Longitudinal Study of Aging and the Genetic and Epigenetic Signatures of Translational Aging Laboratory Testing to look for potential associations between hypertension and cerebral myelin content across 14 white matter brain regions. Myelin content was probed using our advanced multicomponent magnetic resonance relaxometry method of myelin water fraction, a direct and specific magnetic resonance imaging measure of myelin content, and longitudinal and transverse relaxation rates (R1 and R2), 2 highly sensitive magnetic resonance imaging metrics of myelin content. We also applied diffusion tensor imaging magnetic resonance imaging to measure fractional anisotropy, mean diffusivity, radial diffusivity, and axial diffusivity values, which are metrics of cerebral microstructural tissue integrity, to provide context with previous magnetic resonance imaging findings. After adjustment of age, sex, systolic blood pressure, smoking status, diabetes status, and cholesterol level, our results indicated that participants with hypertension exhibited lower myelin water fraction, fractional anisotropy, R1 and R2 values and higher mean diffusivity, radial diffusivity, and axial diffusivity values, indicating lower myelin content and higher impairment to the brain microstructure. These associations were significant across several white matter regions, particularly in the corpus callosum, fronto-occipital fasciculus, temporal lobes, internal capsules, and corona radiata. These original findings suggest a direct association between myelin content and hypertension and form the basis for further investigations including longitudinal assessments of this relationship.

Analysis of the Curative Effect of Diffusion Tensor Imaging-Guided Percutaneous Endoscopic Lumbar Discectomy

Diffusion tensor imaging (DTI), a novel method of describing nerve structure, is a special form of magnetic resonance imaging (MRI). This new imaging method can be used to locate the diseased nerve roots in lumbar disc herniation. The objective of this study is to compare patient outcomes between single-level and doublesection percutaneous endoscopic lumbar discectomy (PELD) in the treatment of lumbar intervertebral disc herniation with single nerve root compression, where single-sided PELD is guided by magnetic resonance diffusion tensor imaging (DTI). The clinical data of patients with lumbar intervertebral disc herniation with double compression of single nerve root symptoms in the Affiliated Hospital of Weifang Medical University from January 2019 to May 2021 were retrospectively summarized and divided into single-level percutaneous endoscopic discectomy (PELD) group after DTI localization and double-section PELD group. The operation time, intraoperative bleeding, VAS score and JOA score of the two groups were compared, as well as the preoperative and postoperative fractional anisotropy (FA) values in the DTI group. The operation time and intraoperative bleeding volume of patients in the DTI group were significantly lower than those in the double segment group, and there was no significant difference between VAS scores and JOA scores in the two groups. After the operation, the nerve root FA value of the responsible compression site of patients in the DTI group increased significantly, but it was still lower than the healthy symmetrical part. The single-level PELD based on DTI has achieved a similar effect to that of the doublesegment PELD in 3 months after the operation, which can improve the FA value of the lesion nerve root. Its bleeding amount is less, and the operation time is shorter, but the efficacy of this technology still requires long-term follow-up of large samples.

Functional and structural networks decoupling in generalized tonic-clonic seizures and its reorganization by drugs.

To investigate potential functional and structural large-scale network disturbances in untreated patients with generalized tonic-clonic seizures (GTCS) and the effects of antiseizure drugs. In this study, 41 patients with GTCS, comprising 21 untreated patients and 20 patients who received antiseizure medications (ASMs), and 29 healthy controls were recruited to construct large-scale brain networks based on resting-state functional magnetic resonance imaging and diffusion tensor imaging. Structural and functional connectivity and network-level weighted correlation probability (NWCP) were further investigated to identify network features that corresponded to response to ASMs. Untreated patients showed more extensive enhancement of functional and structural connections than controls. Specifically, we observed abnormally enhanced connections between the default mode network (DMN) and the frontal-parietal network. In addition, treated patients showed similar functional connection strength to that of the control group. However, all patients exhibited similar structural network alterations. Moreover, the NWCP value was lower for connections within the DMN and between the DMN and other networks in the untreated patients; receiving ASMs could reverse this pattern. Our study identified alterations in structural and functional connectivity in patients with GTCS. The influence of ASMs may be more noticeable within the functional network; moreover, abnormalities in both the functional and structural coupling state may be improved by ASM treatment. Therefore, the coupling state of structural and functional connectivity may be used as an indicator of the efficacy of ASMs.

Predictive values of spinal cord diffusion magnetic resonance imaging to characterize outcomes after contusion injury.

To explore filtered diffusion-weighted imaging (fDWI), in comparison with conventional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI), as a predictor for long-term locomotor and urodynamic (UD) outcomes in Yucatan minipig model of spinal cord injury (SCI). Additionally, electrical conductivity of neural tissue using D-waves above and below the injury was measured to assess correlations between fDWI and D-waves data. Eleven minipigs with contusion SCI at T8-T10 level underwent MRI at 3T 4 h. post-SCI. Parameters extracted from region of interest analysis included Daxial from fDWI at injury site, fractional anisotropy and radial diffusivity from DTI above the injury site along with measures of edema length and cord width at injury site from T2 -weighted images. Locomotor recovery was assessed pre- and weekly post-SCI through porcine thoracic injury behavior scale (PTIBS) and UD were performed pre- and at 12 weeks of SCI. D-waves latency and amplitude differences were recorded before and immediately after SCI. Two groups of pigs were found based on the PTIBS at week 12 (p < 0.0001) post-SCI and were labeled "poor" and "good" recovery. D-waves amplitude decreased below injury and increased above injury. UD outcomes pre/post SCI changed significantly. Conventional MRI metrics from T2 -weighted images were significantly correlated with diffusion MRI metrics. Daxial at injury epicenter was diminished by over 50% shortly after SCI, and it differentiated between good and poor locomotor recovery and UD outcomes. Similar to small animal studies, fDWI from acute imaging after SCI is a promising predictor for functional outcomes in large animals.

White matter microstructural integrity continues to develop from adolescence to young adulthood in mice and humans: Same phenotype, different mechanism

As direct evaluation of a mouse model of human neurodevelopment, adolescent and young adult mice and humans underwent MR diffusion tensor imaging to quantify age-related differences in microstructural integrity of brain white matter fibers. Fractional anisotropy (FA) was greater in older than younger mice and humans. Despite the cross-species commonality, the underlying developmental mechanism differed: whereas evidence for greater axonal extension contributed to higher FA in older mice, evidence for continuing myelination contributed to higher FA in human adolescent development. These differences occurred in the context of species distinctions in overall brain growth: whereas the continued growth of the brain and skull in the murine model can accommodate volume expansion into adulthood, human white matter volume and myelination continue growth into adulthood within a fixed intracranial volume. Appreciation of the similarities and differences in developmental mechanism can enhance the utility of animal models of brain white matter structure, function, and response to exogenous manipulation.

Possibilities neuroimaging and neurophysiological research methods to objectify rehabilitation potential in patients with ischemic stroke (analytical review of the literature)

Cerebral stroke (CS) remains the most important medical and social problem. According to available data, only 25% of stroke survivors return to the premorbid level of daily or work activity, most patients have residual neurological disorders of varying severity. Effective rehabilitation of patients with CS requires not only timely initiation of treatment, but also an individual choice of rehabilitation program. To optimize the rehabilitation strategy in each case, it is necessary to set goals and objectives taking into account the rehabilitation potential (RP) and the prognosis of the patient’s recovery. This paper provides a definition of RP and ways to describe it. The existing neurophysiological methods for assessing the RP of functional recovery after CS, such as electroencephalography, evoked potentials and diagnostic transcranial magnetic stimulation (TMS), are considered. Information about neuroimaging diagnostic methods – computer (CT) and magnetic resonance imaging (MRI) in the context of determining RP is presented. The possibilities of functional and diffusion-t ensor MRI of the brain for assessing RP in various periods of the disease are highlighted in detail. Other possible predictors of the restoration of impaired functions are also considered – the volume and localization of the brain lesion, the patient’s age, cognitive functions and laboratory parameters. Modern complex approaches to the formation of algorithms for the quantitative assessment of RP are described. In particular, the current algorithms for evaluating RP – PREP2 for the upper limb and TWIST for predicting the recovery of walking disorders are described. Currently, there are no generally accepted methods for determining and quantifying RP. The instruments proposed for this purpose are insufficiently sensitive and specific or are not suitable for routine clinical practice.

Application of Magnetic Resonance Diffusion Tensor Imaging in Diagnosis of Lumbosacral Nerve Root Compression

The aim of this study was to assess the value of 3.0T magnetic resonance (MR) Diffusion tensor imaging (DTI) in the diagnosis of lumbosacral nerve root compression. The radiology reports, and clinical records of 34 patients with nerve root compression caused by lumbar disc herniation or bulging and 21 healthy volunteers who had undergone magnetic resonance imaging (MRI) and DTI scan were retrospectively reviewed. The differences in fractional anisotropy (FA) and apparent diffusion coefficient (ADC) between compressed and non-compressed nerve roots from patients and the normal nerve roots from healthy volunteers were compared. Meanwhile, the nerve root fiber bundles were observed and analyzed. The average FA and ADC values of the compressed nerve roots were 0.254 ± 0.307 and 1.892 ± 0.346 10^-3mm2/s, respectively. The average FA and ADC values of the non-compressed nerve roots were 0.377 ± 0.659 and 1.353 ± 0.344 10^-3mm2/s, respectively. The FA value of compressed nerve roots was significantly lower than that of non-compressed nerve roots (P < 0.01). The ADC value of compressed nerve roots was significantly higher than that of non-compressed nerve roots. There were no significant differences between the left and right nerve roots of normal volunteers in FA and ADC values (P > 0.05). The nerve roots at different levels of L3-S1 had significantly different FA and ADC values (P < 0.01). Incomplete fiber bundles with extrusion deformation, displacement or partial defect were observed in the compressed nerve root fiber bundles. The real diagnosis of the clinical situation of the nerve can provide neuroscientists with an important computer tool to help them infer and understand the possible working mechanism from the experimental data of behavior and electrophysiology. The compressed lumbosacral nerve roots can be accurately localized through 3.0T magnetic resonance DTI, which is instructive for accurate clinical diagnosis and preoperative localization.

Feasibility of Diffusion Tensor Imaging for Decreasing Biopsy Rates in Breast Imaging: Interim Analysis of a Prospective Study.

Because of the limited specificity of diagnostic imaging, many breast lesions referred for biopsy turn out to be benign. The objective of this study was to evaluate whether diffusion tensor MRI (DTI) parametric maps can be used to safely avoid biopsy of breast lesions. Individuals referred for breast biopsy based on mammogram (MG), ultrasound (US), and/or contrast enhanced (CE)-MRI were recruited. Scans consisting of T2-weighted and DTI sequences were performed. Multiple DTI-derived parametric color maps were evaluated semi-quantitatively to characterize lesions as "definitely benign," "not definitely benign," or "suspicious." All patients subsequently underwent biopsy. In this moderately-sized prospective study, 21 out of 47 pathologically proven benign lesions were characterized by both readers as "definitely benign," which would have precluded the need for biopsy. Biopsy was recommended for 11 out of 13 cancers that were characterized as "suspicious." In the remaining two cancers and 26 of 47 benign lesions, the scans were characterized as "not definitely benign" and hence required biopsy. The main causes for "not definitely benign" scans were small lesion sizes and noise. The results suggest that in appropriately selected patients, DTI may be used to safely reduce the number of unnecessary breast biopsies.

Magnetic Resonance Diffusion Tensor Imaging Characterize the Hepatic Ischemia-Reperfusion Injury in an Animal Study

Hepatic ischemia-reperfusion (I/R) injury is the main cause of morbidity and mortality after hepatectomy; thus, new methods for reducing I/R injury are required. The aim of this study is to evaluate changes in the average apparent diffusion coefficient (ADCavg) and fractional anisotropy (FA) in rabbits with partial hepatic I/R injury with magnetic resonance diffusion tensor imaging (DTI). The left lobe of the rabbit liver underwent 60 minutes of ischemia followed by 0.5, 2, 6, 12, 24, and 48 hours of reperfusion. T2-weighted images (T2WI), T1-weighted images (T1WI), DTI, and contrast-enhanced T1WI were performed; 6 b values were used for DTI on 6 diffusion directions. The serum levels of transaminases and liver histopathology findings were examined. In the early stage of I/R (0.5 hour), ADCavg decreased significantly and increased sharply to 2 hours, then increased from 6 hours to 48 hours of reperfusion, except for a transient decrease (24 hours). Meanwhile, FA showed almost the opposite trend, drastically increasing during the first 0.5 hour and then slightly decreasing until 48 hours of reperfusion, except for an obvious decrease in the 2-hours group. The serum levels of liver markers and the pathologic scores were sharply increased in the I/R group after reperfusion and correlated with DTI of hepatic tissue after I/R. Diffusion tensor imaging is feasible for imaging I/R-induced liver damage and can discriminate isotropic properties of the liver after I/R injury with objective changes in the ADCavg and FA. Diffusion tensor imaging can be a promising novel approach for use in clinical management after liver surgery.

Anatomical and Functional Connectivity of Critical Deep Brain Structures and Their Potential Clinical Application in Brain Stimulation

Subcortical structures, such as the hippocampus, amygdala, and nucleus accumbens (NAcc), play crucial roles in human cognitive, memory, and emotional processing, chronic pain pathophysiology, and are implicated in various psychiatric and neurological diseases. Interventions modulating the activities of these deep brain structures hold promise for improving clinical outcomes. Recently, non-invasive brain stimulation (NIBS) has been applied to modulate brain activity and has demonstrated its potential for treating psychiatric and neurological disorders. However, modulating the above deep brain structures using NIBS may be challenging due to the nature of these stimulations. This study attempts to identify brain surface regions as source targets for NIBS to reach these deep brain structures by integrating functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI). We used resting-state functional connectivity (rsFC) and probabilistic tractography (PTG) analysis to identify brain surface stimulation targets that are functionally and structurally connected to the hippocampus, amygdala, and NAcc in 119 healthy participants. Our results showed that the medial prefrontal cortex (mPFC) is functionally and anatomically connected to all three subcortical regions, while the precuneus is connected to the hippocampus and amygdala. The mPFC and precuneus, two key hubs of the default mode network (DMN), as well as other cortical areas distributed at the prefrontal cortex and the parietal, temporal, and occipital lobes, were identified as potential locations for NIBS to modulate the function of these deep structures. The findings may provide new insights into the NIBS target selections for treating psychiatric and neurological disorders and chronic pain.

Mechanical stiffness and anisotropy measured by MRE during brain development in the minipig

The relationship between brain development and mechanical properties of brain tissue is important, but remains incompletely understood, in part due to the challenges in measuring these properties longitudinally over time. In addition, white matter, which is composed of aligned, myelinated, axonal fibers, may be mechanically anisotropic. Here we use data from magnetic resonance elastography (MRE) and diffusion tensor imaging (DTI) to estimate anisotropic mechanical properties in six female Yucatan minipigs at ages from 3 to 6 months. Fiber direction was estimated from the principal axis of the diffusion tensor in each voxel. Harmonic shear waves in the brain were excited by three different configurations of a jaw actuator and measured using a motion-sensitive MR imaging sequence. Anisotropic mechanical properties are estimated from displacement field and fiber direction data with a finite element- based, transversely-isotropic nonlinear inversion (TI-NLI) algorithm. TI-NLI finds spatially resolved TI material properties that minimize the error between measured and simulated displacement fields. Maps of anisotropic mechanical properties in the minipig brain were generated for each animal at all four ages. These maps show that white matter is more dissipative and anisotropic than gray matter, and reveal significant effects of brain development on brain stiffness and structural anisotropy. Changes in brain mechanical properties may be a fundamental biophysical signature of brain development.