Maryam Tayebi

Purpose: Finite element (FE) models are widely used to study traumatic brain injury, but most are based on single-subject scans or generic atlases that may not represent specific cohorts, introducing variability in biomechanical outputs. This study presents a reproducible framework for generating a cohort-specific MRI-derived template brain and constructing a representative FE head model. Methods: A cohort-specific template was created from T1-weighted and diffusion-weighted MRI scans of collision sport athletes ( n = 78). An FE head model was then generated from this template, with material properties mapped using MRI-derived microstructural information. The anatomical accuracy of the template was evaluated using deformation-based morphometry against standard brain atlases. The FE model was validated against cadaveric head impact experiments. Subject-specific FE models were also developed to test the pipeline’s applicability and model performance. Results: Registration of an external non-collision sport controls ( n = 20) to the template showed reduced deformation compared with registration to the MNI152 and an existing adolescent atlas, indicating improved cohort representation. Validation against cadaveric data demonstrated small to moderate correlations between simulated and experimental nodal displacements. The subject-specific model showed significantly different strain distributions from isotropic and fiber dispersion-informed models at both impact intensities; the two template models did not differ significantly. Conclusion: The proposed framework enables reproducible construction of cohort-specific FE brain models using open-access tools. Results highlight the importance of subject- and cohort-specific modeling for accurately characterizing brain biomechanics. This approach improves the anatomical and microstructural realism of FE models and supports more precise mapping of mechanical strain to clinical outcomes in TBI.

Collision and contact-sport athletes are repeatedly exposed to subconcussive head impacts or subclinical head acceleration events (HAEs), which are impacts that do not result in a clinical diagnosis of mild traumatic brain injury but may induce subtle neurological alterations. These effects may include structural, functional, and metabolic changes within the brain. Various exposure quantification techniques have been developed to characterise HAE exposure, while diffusion MRI enables assessment of brain microstructural organisation, with changes in diffusion-derived metrics associated with pathophysiological processes. This systematic review was conducted in accordance with PRISMA guidelines to evaluate the use of various HAE exposure quantification techniques, exposure weighting approaches, and diffusion MRI in characterising the relationship between HAE exposure and brain microstructure in athletes. Across studies, longitudinal findings for fractional anisotropy (FA), mean (MD), axial (AD), and radial diffusivity (RD) were inconsistent, and substantial heterogeneity in exposure quantification methods and analyses was observed. However, quantitative analysis demonstrated a significant negative association between total subclinical HAE count across the season and FA, and a positive association with MD, suggesting cumulative microstructural alteration. Exposure metrics—including risk-weighted, time-weighted, and finite-element-derived strain measures—showed stronger associations with diffusion MRI alterations than simple impact counts or peak acceleration measures. However, HAE exposure risk models are sport-specific and require broader validation for applicability across sporting cohorts. Future studies should reduce methodological heterogeneity, control for confounding variables, and refine exposure quantification and weighting approaches to better understand the relationship between repetitive subclinical HAE exposure and WM microstructural integrity.

Purpose: Finite element (FE) models are widely used to study traumatic brain injury, but most are based on single-subject scans or generic atlases that may not represent specific cohorts, introducing variability in biomechanical outputs. This study presents a reproducible framework for generating a cohort-specific MRI-derived template brain and constructing a representative FE head model. Methods: A cohort-specific template was created from T1-weighted and diffusion-weighted MRI scans of collision sport athletes (n = 78). An FE head model was then generated from this template, with material properties mapped using MRI-derived microstructural information. The anatomical accuracy of the template was evaluated using deformation-based morphometry against standard brain atlases. The FE model was validated against cadaveric head impact experiments. A subject-specific FE model was also developed to test the pipeline’s applicability and model performance. Results: Registration of an external non-collision sport controls (n = 20) to the template showed reduced deformation compared with registration to the MNI152 and an existing adolescent atlas, indicating improved cohort representation. Validation against cadaveric data demonstrated small to moderate correlations between simulated and experimental nodal displacements. Subject-specific and fiber dispersion-informed models showed significantly different strain distributions compared with isotropic models under low-intensity impacts, but no significant differences under high-intensity impacts. Conclusion: The proposed framework enables reproducible construction of cohort-specific FE brain models using open-access tools. Results highlight the importance of subject-and cohort-specific modelling for accurately characterizing brain biomechanics. This approach improves the anatomical and microstructural realism of FE models and supports more precise mapping of mechanical strain to clinical outcomes in TBI. STATEMENTS AND DECLARATIONS: We declare that we have no financial or personal relationships with individuals, companies, or organisations that could inappropriately influence the content of this work. We also confirm that we hold no professional or personal interests in any product, service, or company that could be perceived as affecting the content and quality of this manuscript.

Ultra-high contrast (UHC) MRI describes forms of MRI in which little or no contrast is seen on conventional MRI images but very high contrast is seen with UHC techniques. One of these techniques uses the divided subtracted inversion recovery (dSIR) sequence, which, in modelling studies, can produce ten times the contrast of conventional inversion recovery (IR) sequences. When used in cases of mild traumatic brain injury (mTBI), the dSIR sequence frequently shows extensive abnormalities in white matter that appears normal when imaged with conventional T₂-fluid-attenuated IR (T₂-FLAIR) sequences. The changes are bilateral and symmetrical in white matter of the cerebral and cerebellar hemispheres. They partially spare the anterior and posterior central corpus callosum and peripheral white matter of the cerebral hemispheres and are described as the whiteout sign. In addition to mTBI, the whiteout sign has also been seen in methamphetamine use disorder and Grinker’s myelinopathy (delayed post-hypoxic leukoencephalopathy) in the absence of abnormalities on T₂-FLAIR images, and is a central component of post-insult leukoencephalopathy syndromes. This paper describes the concept of ultra-high contrast MRI, the whiteout sign, the theory underlying the use of dSIR sequences and post-insult leukoencephalopathy syndromes.

In modelling studies targeted MRI (tMRI) of small increases in the T1 of tissues using divided Subtracted Inversion Recovery (dSIR) sequences show ten or more times the contrast seen with conventional IR sequences. This may be particularly useful in imaging normal appearing white matter where there may be small changes in T1 and/or T2 in disease but these changes may be insufficient to produce useful contrast with conventional T2-weighted spin echo (T2-wSE) and T2-FLuid Attenuated Inversion Recovery (T2-FLAIR) sequences. In a case of recurrent mild Traumatic Brain Injury (mTBI), very extensive high contrast abnormalities were seen in white matter using a dSIR sequence that targeted small increases in T1 in areas where no abnormality was apparent with T2-wSE or T2-FLAIR sequences. The increases in T1 may be due to neuroinflammation and/or degeneration which produces the abnormalities seen on the dSIR images. tMRI of normal appearing white matter may have widespread application in clinical MRI of the brain.

Increasing evidence for the cumulative effects of head trauma on structural integrity of the brain has emphasized the need to understand the relationship between tissue mechanic properties and injury susceptibility. Here, diffusion tensor imaging, helmet accelerometers and amplified magnetic resonance imaging were combined to gather insight about the region-specific vulnerability of the corpus callosum to microstructural changes in white-matter integrity upon exposure to sub-concussive impacts. A total of 33 male Canadian football players (mean_age = 20.3 ± 1.4 years) were assessed at three time points during a football season (baseline pre-season, mid-season and post-season). The athletes were split into a LOW (N = 16) and HIGH (N = 17) exposure group based on the frequency of sub-concussive impacts sustained on a per-session basis, measured using the helmet-mounted accelerometers. Longitudinal decreases in fractional anisotropy were observed in anterior and posterior regions of the corpus callosum (average cluster size = 40.0 ± 4.4 voxels; P < 0.05, corrected) for athletes from the HIGH exposure group. These results suggest that the white-matter tract may be vulnerable to repetitive sub-concussive collisions sustained over the course of a football season. Using these findings as a basis for further investigation, a novel exploratory analysis of strain derived from sub-voxel motion of brain tissues in response to cardiac impulses was developed using amplified magnetic resonance imaging. This approach revealed specific differences in strain (and thus possibly stiffness) along the white-matter tract (P < 0.0001) suggesting a possible signature relationship between changes in white-matter integrity and tissue mechanical properties. In light of these findings, additional information about the viscoelastic behavior of white-matter tissues may be imperative in elucidating the mechanisms responsible for region-specific differences in injury susceptibility observed, for instance, through changes in micro-structural integrity following exposure to sub-concussive head impacts.

Introduction: A hiatal hernia can be classified as one of four types according to the position of the gastroesophageal (GE) junction and the extent of herniated stomach. Type IV paraesophageal hiatal hernia (PEHH) is characterized by a large defect in the diaphragmatic hiatus that allows other organs, besides stomach, such as the colon, pancreas, spleen, or small intestine to herniate into the thorax. Herniation of the pancreas through a gastroesophageal hiatus is a rare condition, and only a few cases have been reported in the literature. Case report: We present a case of an asymptomatic patient with paraesophageal herniation along with the body and tail of the pancreas. Conclusion: However, surgery is optimal choice for symptomatic patients, it is important for surgeons to consider the risks of different approaches and choose the best intervention.

Breast and endometrial cancer are the most common types of female cancers, but the incidence of both of these malignancies in a single patient is a rare event. Multiple primary malignancy has been increasingly reported over the past decade, and double primary cancer is considered as the most common type. In this study, we present a 53-year-old woman with synchronous primary malignancy of breast and endometrium. This patient had a history of breast and endometrial cancer in her family. Mammography and chest CT of the patient revealed a mass in the right breast and left supraclavicular region. However, the patient did not want to initiate treatment. Subsequently, the patient returned with a chief complaint of persistent abnormal vaginal bleeding. Abdominopelvic CT scan of the patient revealed a huge soft tissue mass in the pelvic cavity. She underwent hysterectomy, and pathology revealed endometrioid carcinoma, which had invaded the full thickness of uterine wall. Since this type of malignancy is rare and several risk factors are associated with it, it is worth being considered by clinicians when making decisions about screening or strategy for prevention.