Publication collection
White matter asymmetry changes with age and depends on which tissue or pathway feature is measured. Using 35,120 individuals from 50 studies, this work charts 30 paired pathways from birth to 100 years. It provides a reference for interpreting lateralization across development and aging.
White matter growth charts built from 35,120 brain scans provide reference trajectories from birth to 100 years. The study measures tissue properties and pathway shape across 72 tracts, enabling age- and sex-adjusted comparisons. Public models, processing tools, and shareable derived data support independent use of the charts.
At 0.9 mm resolution on a NexGen 7T scanner, this study compares 11 time-matched diffusion acquisition and correction strategies. Four-direction phase encoding provides the strongest geometric fidelity and repeatability in five adults scanned twice. The findings inform high-resolution protocols for both fine superficial connections and long-range pathways.
Anatomical evidence from primate tract tracing guides reconstruction of short connections within the living human prefrontal cortex. The study maps 91 connections in 1,003 participants, finding reproducible individual patterns and substantial variation between people. It offers a framework for studying local circuitry using anatomically informed diffusion tractography.
This review explains how modern diffusion MRI preprocessing improves the anatomical fidelity and repeatability of tractography. It brings together evidence for denoising and correction of motion, eddy currents, susceptibility distortion, and Gibbs ringing. Practical acquisition advice and integrated pipelines help researchers apply these methods consistently.
Tractography can probe organized tissue far beyond cerebral white matter. This review surveys applications in the spinal cord, heart, peripheral nerves, brachial plexus, kidney, skeletal muscle, and prostate. It explains the acquisition and modeling adaptations each region requires, together with the anatomical opportunities and unresolved interpretation challenges.
Atlas templates and subject-specific tractography answer overlapping but different anatomical questions. This debate article explains the strengths of standardized population references and individual pathway reconstruction. It outlines why methodological choices should follow the research question, especially when individual variation and pathway geometry are central to an analysis.
Short association fibers are numerous but challenging to reconstruct because of their small size, variable anatomy, and partial volume effects. This communication summarizes key anatomical and methodological insights. It describes how better images, adapted processing, and suitable tracking parameters are opening the superficial white matter to investigation.
This study compares the development of short association fibers and long-range pathways in 616 participants aged 5.6–21.9 years. Diffusion tensor and NODDI measurements reveal shared age-related patterns alongside distinct features of superficial white matter. The results provide a reference for future studies of atypical development.
This short communication examines how animal models inform human tractography, drawing on a debate at the 2024 Tract-Anat Retreat. It highlights histological validation, high-resolution imaging, disease research, and comparative anatomy. The discussion also addresses species differences and the care required when translating findings to humans.
Diffusion and susceptibility-weighted imaging reveal how white matter pathways relate to the orientation of nearby blood vessels. Vessels often align with some local fiber populations but do not consistently follow the dominant tract direction or an entire pathway. The findings help interpret MRI contrasts influenced by both vascular and axonal geometry.
The first paper in the ISMRM preclinical diffusion MRI series presents community recommendations for imaging living small animals. It covers model selection, preparation, acquisition, processing, and interpretation, with an emphasis on reproducibility. The authors also identify open methodological questions and resources for sharing data and software.
The third ISMRM preclinical diffusion MRI paper addresses ex vivo image processing, comparisons with microscopy, and tractography. It explains how fixed-tissue experiments require choices that differ from in vivo workflows. Community recommendations and unresolved questions guide the design and interpretation of rigorous, reproducible validation studies.
This handbook chapter introduces the foundations of tractography validation and the roles of numerical simulations and physical phantoms. It explains how controlled reference systems can test reconstruction methods at different anatomical scales. The discussion helps researchers choose validation strategies and understand the limits of their conclusions.
The second tractography-validation chapter reviews anatomical reference systems, empirical validation when ground truth is unavailable, and ways to quantify agreement. It connects validation in real tissue with the practical interpretation of reconstructed pathways.
This handbook chapter synthesizes what validation studies have taught us about tractography. Evidence from simulations, phantoms, histology, and anatomical comparisons reveals both reliable capabilities and persistent limitations. The chapter connects complex tissue anatomy and reconstruction assumptions to the practical interpretation and continued development of diffusion MRI tractography.
Short superficial white matter pathways show widespread age-related diffusion changes and regionally varying reductions in length and volume. Data from 1,293 participants distinguish changes in fibers connecting neighboring gyri from those running within a gyrus, extending aging research beyond long-range bundles.
Imaging from 2,421 people aged 5–100 maps how the thickness and volume of superficial white matter vary across the brain and lifespan. These features follow region-specific trajectories and relate to cortical thickness and curvature, adding an often-missing component to descriptions of brain maturation and aging.
Across 2,789 imaging sessions spanning ages 0–100, this study links tract microstructure, tract geometry, and the morphology of connected cortex. Different features and pathways mature and decline on different schedules, and developmental age associations are related to patterns observed during aging.
Across 1,218 older adults, diffusion measurements and tract shape both changed with age. Microstructural trends were relatively widespread, while volume, length, and surface-area changes differed more across pathways, suggesting that bundle geometry adds complementary information about aging.
Distinct white matter bundles frequently share the same local orientation before diverging, creating ambiguities that better crossing-fiber detection cannot resolve. This study maps such bottlenecks across the brain and finds them throughout major pathway classes, including regions often described as containing a single fiber orientation.
Four bundle-segmentation workflows reveal how scanner, vendor, and acquisition changes affect white matter measurements. Spatial resolution was a major acquisition confound, while differences between segmentation workflows exceeded every other tested source of variation, particularly near the cortex.
Pandora provides population-based maps of 216 white matter bundles derived from 2,443 people using six automated tractography approaches. Its overlapping bundle representations support anatomical localization and comparison across studies without treating white matter as a single uniform region.
Forty-two teams dissected fourteen bundles from identical tractograms, revealing large differences in what researchers call the same pathway. Variation between dissection protocols exceeded within-protocol and between-person variation, demonstrating the need for clearer anatomical definitions and reproducible segmentation rules.
Anatomical inclusion and exclusion constraints substantially improve tractography in a previously studied validation dataset. The results demonstrate that high sensitivity and specificity can coexist when prior pathway knowledge is available, while also showing why this best-case setting differs from discovering unknown connections.
A fiber coherence index detects incorrectly flipped or permuted diffusion gradient tables by testing whether neighboring fiber orientations agree. Validation across research, clinical, and animal scans supports its use as an automated quality-control check.
CHIASM combines structural MRI, diffusion MRI, histological stains, and motor-cortex tracing in a common squirrel monkey reference space. The integrated atlas lets researchers compare tissue appearance across modalities and use labeled cortical regions and white matter pathways for anatomical localization.
Forty commonly used tractography configurations were tested against motor-cortex tracer anatomy in squirrel monkeys. Accuracy depended strongly on reconstruction, tracking, and seeding choices, and deteriorated with distance from the seed; some methods missed substantial parts of known pathways.
This review synthesizes a decade of tractography benchmark competitions. Physical phantoms, simulated data, and anatomical references reveal recurring tradeoffs between finding true pathways and avoiding false connections, while showing how acquisition, reconstruction, seeding, and evaluation choices shape apparent performance.
HARFI estimates the directional structure of correlations in white matter BOLD signals without restricting them to a tensor. Its sampling approach reduces orientation bias and represents bending or fanning patterns, providing a functional MRI complement to diffusion-based descriptions of white matter pathways.
Histology from three squirrel monkey brains shows that diffusion MRI fiber response functions vary across white matter regions. Choosing a different response function changes reconstructed fiber orientations and can alter tractography accuracy.
The 3D-VoTEM challenge tested 176 tractography submissions against a physical phantom and two ex vivo brain references. Despite modern modeling and tracking methods, substantial anatomical errors persisted across these complementary tests, demonstrating that algorithmic sophistication alone does not guarantee accurate connectivity.
Comparing tractography with myelin-stained histology confirms that streamlines preferentially terminate on gyral crowns. The bias persists across tracking algorithms, diffusion models, weightings, and high-resolution acquisitions, complicating interpretation of cortical connectivity from streamline density.
Histological validation compares several diffusion reconstruction methods against three-dimensional fiber geometry. Models captured overall angular structure better than discrete peak counts or low-angle crossings, and no method led across all accuracy criteria; dispersion estimates also showed limited agreement with histology.
Ex vivo diffusion MRI and matched histology challenge the assumption that smaller voxels eliminate crossing fibers. Across the tested scales, finer resolution revealed more complex orientations, indicating that tissue geometry remains a fundamental obstacle even when image resolution improves.
Repeated scans test how short clinical q-ball acquisitions balance diffusion weighting, direction count, and model complexity. The analysis shows that spherical harmonic order strongly affects derived metrics and that adding directions can be more useful than repeating measurements within a fixed scan time.
VALiDATe29 provides a common anatomical reference built from MRI of 29 squirrel monkeys. Structural, diffusion, and ex vivo templates are paired with cortical and white matter labels to support registration, regional measurements, and comparisons across animals and experiments.
Three-dimensional confocal microscopy provides a direct reference for testing diffusion MRI estimates of fiber orientation. Comparisons with constrained spherical deconvolution found good agreement for nearly parallel fibers but larger errors in crossing regions, including failure to resolve crossings below 60 degrees in this dataset.
