Johns Hopkins Biomedical Engineering

Remote photoplethysmography (rPPG) for heart rate (HR) measurement based on facial videos has recently attracted increasing attention. However, most existing methods focus on average heart rate (AHR) over a period rather than instantaneous heart rate (IHR), which better reflects physical and mental states. To address this issue, we propose a novel rPPG-based method for measuring IHR values from facial videos. Our method employs the wavelet synchrosqueezed transform (WSST) to generate time-frequency representations (TFRs) of chrominance (CHROM) signals from multiple facial regions of interest (ROIs), synchronously reflecting the IHR during a video segment. Furthermore, the TransUNet is introduced to refine these TFR images, enhancing the ridge line information related to IHRs. Comprehensive comparisons and ablation studies on four public datasets (UBFC-rPPG, PURE, UBFC-Phys, and MMPD) reveal that our WSST-UNet method achieves superior performance over several typical rPPG methods, achieving mean absolute errors (MAE) of 2.34 beats per minute (bpm), 1.29 bpm, 5.03 bpm, and 6.58 bpm, respectively. The proposed method offers a promising solution for practical application in video-based IHR measurements.

Purpose/Objective(s) Re-irradiation is increasingly utilized in modern radiation oncology in order to treat secondary recurrence and metastatic disease, yet accurate estimation of cumulative lifetime dose to organs at risk remains a major obstacle in safe treatment planning. Existing approaches use deformable image registration (DIR) techniques but are typically patient-specific, limited by imaging field-of-view, and inconsistent across institutions, restricting development of cumulative dose constraints supported by scientific evidence. We propose a standardized, phantom-based workflow for whole-body lifetime dose assessment to improve safety, comparability, and clinical integration. Materials/Methods A deformable dose accumulation workflow was developed to map radiotherapy dose distributions from multiple treatment courses onto the International Commission on Radiological Protection (ICRP) mesh-based whole-body reference phantoms, establishing a unified anatomical coordinate system independent of treatment site or posture. Intermediate anthropomorphic phantom variants were incorporated to reduce geometric discrepancies and preserve spatial dose fidelity. DIR performance was evaluated using geometric and dosimetric metrics, including dose-volume histogram (DVH) comparisons and a novel subregional dose evaluation tool designed to detect localized dose discrepancies independent of the deformation vector field. Cumulative doses were converted to EQD2 incorporating tissue recovery time–dependent models accounting for tissue repair between treatment courses to enhance clinical relevance. Results A collection of patient dose distributions were successfully mapped onto the whole-body ICRP reference phantoms. DVH analysis demonstrated similar or improved dosimetric agreement when mapping patient doses to the reference phantom compared with mapping to a secondary CT scan from the same patient. In a representative case, mean dose differences across multiple critical organs were within 9% following deformation to the phantom, whereas mapping the same distribution onto a secondary CT scan of the same patient yielded mean differences of approximately 14%. Conclusion A standardized phantom-based workflow for cumulative dose assessment is technically feasible and clinically relevant. By enabling reproducible lifetime dose tracking using the ICRP standard reference phantom, this approach strengthens toxicity modeling, supports development of clinically validated re-irradiation constraints, and enhances patient safety. Clinically, it may facilitate more informed retreatment decision-making, improve risk stratification and patient counseling, and promote consistent cumulative dose reporting across institutions, thereby advancing the safety and scientific rigor of re-irradiation practice.

We combine experiments and computational fluid dynamics to analyze in detail the hydraulic permeability of a new class of architected porous media called bijel-templated materials (BTMs), which are derived from the arrested spinodal decomposition of particle-stabilized emulsions. We benchmark our findings against particletemplated materials (PTMs), a class of porous media commonly used in technological applications. Despite similar pore sizes and porosities, BTMs exhibit up to a five-fold higher geometric throughput factor, reflecting their continuous, minimally constricting channel network. The decomposition of permeability into a size term and a topology-sensitive multiplier reveals that BTMs are size-dominated: once the characteristic channel size or radius of curvature is defined, permeability scales predictably without incurring additional topological penalties. By contrast, PTMs depend on both size and topology: although permeability scales with pore size, it is further modulated by porosity, constrictivity, and tortuosity arising from microstructural bottlenecks, which must be considered independently of pore size. Furthermore, BTMs preserve percolation at significantly lower porosities than PTMs, highlighting their inherent resilience in connectivity and demonstrating how spinodal bicontinuity enables efficient fluid transport. These findings reveal that bijel-derived architectures define a distinct morphological regime of flow, in which hydraulic permeability is governed by curvature and bicontinuity rather than traditional porosity-tortuosity scaling.

Introduction:Patients with diffuse lung disease (DLD) undergo CT scans for diagnosis and evaluation. Attempts to characterize the radiographic appearance of these regions with quantitative features like radiomics have been hindered by variability in CT acquisition and reconstruction parameters. The purpose of this investigation is to characterize the effect of CT reconstruction kernel on radiomic features in normal and fibrotic regions in DLD patients. Methods:Raw CT projection data of DLD patients receiving a thoracic CT exam was collected from 3 CT scanners (Definition AS, Flash, and Force; Siemens Healthineers, Forchheim, Germany) and retrospectively reconstructed with 5 reconstruction kernels (smooth, medium-smooth, medium, medium-sharp, and sharp). The medium kernel is part of the clinical protocol at our institution and considered the reference kernel for this investigation. Regions of classic normal and classic fibrosis were annotated by 2 thoracic radiologists on images reconstructed with reference kernels. The annotations were copied across each reconstruction, and 72 radiomic features were extracted from each annotation using Pyradiomics. Agreement between features in reference and non-reference kernels was assessed with concordance correlation coefficient (CCC). Features were considered robust if average CCC was > 0.9. Results:There were 66 patients included with 116 regions of normal and 208 regions of fibrosis annotated across all patients. Across kernels in normal tissue, 0/16 GLSZM, 1/16 GLRLM, 0/22 GLCM, and 5/18 first-order features were robust (average CCC > 0.9). Across kernels in fibrotic tissue, 1/16 GLSZM, 3/16 GLRLM, 3/22 GLCM, and 7/18 first-order features were robust, however the effect magnitude of sharper kernels was greater than in normal tissue. Conclusion:First-order features were more robust than other features; GLCM features were the least robust. There are more robust features across kernels in fibrotic tissue, but the magnitude of kernel effect is greater in fibrotic tissue than in normal tissue.

BackgroundAlzheimer's disease (AD) is the most common form of dementia, characterized by the accumulation of amyloid-β (Aβ) plaques and hyperphosphorylated tau tangles. The locus coeruleus (LC) is among the first brain regions to show degeneration and tau pathology during the early stages of AD. Previous studies have demonstrated that short-term chemogenetic LC stimulation can improve memory performance in the TgF344-AD rat model, while long-term norepinephrine reuptake inhibition can worsen memory deficits in the ADLPTau mouse model. However, the effects of long-term LC stimulation in tau mouse models on memory, synaptic plasticity, and tauopathy remain unclear.ObjectiveTo evaluate the impact of long-term LC stimulation on memory, synaptic plasticity, and tauopathy in PS19 mice using behavioral paradigms, electrophysiological recordings, and immunofluorescence analysis.MethodsThe radial arm water maze and fear conditioning test were conducted to assess memory performance in PS19 mice with and without long-term LC stimulation. Hippocampal long-term potentiation (LTP) was recorded to evaluate the effect of long-term LC stimulation on synaptic plasticity. Immunofluorescence was employed to examine tau phosphorylation, neurodegeneration, and neuroinflammation.ResultsLong-term LC stimulation in PS19 mice exacerbated spatial memory deficits in the water maze, impaired contextual fear memory, reduced hippocampal LTP, and increased asparagine endopeptidase (AEP) expression, tau hyperphosphorylation, and neuroinflammation.ConclusionsLong-term LC stimulation may exacerbate memory deficits in PS19 mice by impairing synaptic plasticity and increasing neural degeneration in the hippocampus. Increased AEP expression and tau hyperphosphorylation in the LC further suggest a possible association between LC overactivation and AEP-associated tau pathology.