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Sports-related concussion is a major public health problem in the United States and yet its biomechanical mechanisms remain unclear. In vitro studies demonstrate axonal elongation as a potential injury mechanism; however, current response-based injury predictors (e.g., maximum principal strain, ε(ep)) typically do not incorporate axonal orientations. We investigated the significance of white matter (WM) fiber orientation in strain estimation and compared fiber strain (ε(n)) with ε(ep) for 11 athletes with a clinical diagnosis of concussion. Geometrically accurate subject-specific head models with high mesh quality were created based on the Dartmouth Head Injury Model (DHIM), which was successfully validated (performance categorized as "good" to "excellent"). For WM regions estimated to be exposed to high strains using a range of injury thresholds (0.09-0.28), substantial differences existed between ε(n) and ε(ep) in both distribution (Dice coefficient of 0.13-0.33) and extent (∼ 5-10-fold differences), especially at higher threshold levels and higher rotational acceleration magnitudes. For example, an average of 3.2% vs. 29.8% of WM was predicted above an optimal threshold of 0.18 established from an in vivo animal study using ε(n) and ε(ep), respectively, with an average Dice coefficient of 0.14. The distribution of WM regions with high ε(n) was consistent with typical heterogeneous patterns of WM disruptions in diffuse axonal injury, and the group-wise extent at the optimal threshold matched well with the percentage of WM voxels experiencing significant longitudinal changes of fractional anisotropy and mean diffusivity (3.2% and 3.44%, respectively) found from a separate independent study. These results suggest the significance of incorporating WM microstructural anisotropy in future brain injury studies.

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X‐ray detectors are widely utilized in medical diagnostics and nondestructive product inspection. Halide perovskites are recently demonstrated as excellent candidates for direct X‐ray detection. However, it is still challenging to obtain high quality perovskites with millimeter‐thick over a large area for high performance, stable X‐ray detectors. Here, methylammonium bismuth iodide (MA3Bi2I9) polycrystalline pellets (PPs) are developed by a robust, cost effective, and scalable cold isostatic‐pressing for fabricating X‐ray detectors with low limit of detection (LoD) and superior operational stability. The MA3Bi2I9‐PPs possess a high resistivity of 2.28 × 1011 Ω cm and low dark carrier concentration of ≈107 cm−3, and balanced mobility of ≈2 cm2 V−1 s−1 for electrons and holes. These merits enable a sensitivity of 563 μC Gyair−1 cm−2, a detection efficiency of 28.8%, and an LoD of 9.3 nGyair s−1 for MA3Bi2I9‐PPs detectors, and the LoD is much lower than the dose rate required for X‐ray diagnostics used currently (5.5 μGyair s−1). In addition, the MA3Bi2I9‐PPs detectors work stably under high working bias field up to 2000 V cm−1 after sensing an integrated dose >320 Gyair with continuous X‐ray radiation, demonstrating its competitive advantage in practical application. These findings provide an approach to explore a new generation of low LoD, stable and green X‐ray detectors based on MA3Bi2I9‐PPs.