Annals of Biomedical Engineering最新文献

Objective

To determine the biomechanical properties of the central corneal region under intraocular pressure (IOP) and to develop an accurate method for predicting the corresponding responses.

Methods

In the rabbit corneal inflation test, a calculation method for the biomechanical properties in the thickness direction of the cornea was proposed. The corresponding stress–strain relationship was obtained from the change in the central corneal thickness and IOP. Finite element analysis (FEA) was utilized to predict the biomechanical responses of the central corneal region under IOP using the derived stress–strain relationship. The FEA predictions using the stress–strain relationships derived from the uniaxial tensile test and optical coherence elastography (OCE) were also conducted for comparison.

Results

The prediction accuracy of the FEA based on the inflation test was evaluated against OCE (in-plane), OCE (out-of-plane), and uniaxial tensile test. Compared to these methods, the maximum deviation of the apex displacement prediction based on the inflation test decreased by 73.2, 88.4, and 64.4%, respectively, and the maximum deviation of the central curvature prediction decreased by 89.2, 30.7, and 49.7%, respectively.

Conclusion

The stress–strain relationship in the thickness direction of the cornea can provide the most accurate prediction result of the corneal biomechanical responses under IOP. The inflation test-based method proposed can serve as an accurate tool for biomechanical characterization of the central corneal region.

To promote the adoption of exoskeletons in industries aiming to prevent work-related musculoskeletal disorders, it is essential to demonstrate their positive impact for specific tasks and users through practical evaluation methods. This study assessed four methods, each with a different level of detail, for modeling the support provided by a hinge-type back-support exoskeleton in OpenSim. Methods 1 and 2 simulated support as a pure torque applied at the hip joint, with Method 1 relying on user kinematics, and Method 2 using exoskeleton movement data to estimate the torque profile. Method 3 estimated supporting force vectors based on user kinematics and exoskeleton configuration, assuming the user’s body and the exoskeleton moved together. Method 4 incorporated the movement of the exoskeleton to simulate support as force vectors and was used as the reference for comparison. Results for back muscle activity and L5-S1 joint reaction forces were compared across the four modeling methods using data from fourteen participants performing squatting and stooping tasks with the exoskeleton. Statistical parameter mapping revealed significant differences in L5-S1 joint reaction forces between Methods 1 and 2 compared to Method 4 throughout the exoskeleton engagement period during squatting, and at the peak trunk angle during stooping. In contrast, minimal differences were observed between Method 3 and Method 4. These findings suggest that modeling exoskeleton support as force vectors based on user kinematics (Method 3) provides reasonable accuracy, demonstrating the feasibility of evaluating exoskeleton support with reduced data collection complexity and enabling an efficient assessment process.

Patient-specific mandibular reconstruction plates (PSMRPs) have gained prominence for their precise adaptation to mandibular contours and reported enhanced mechanical performance compared to the manual-bent mandibular reconstruction plates (MBMRPs). However, clinical adoption remains cautious due to insufficient biomechanical evidence directly and carefully comparing their performance. Hence, this study investigated the biomechanical behavior between two mandibular reconstruction assemblies with MBMRP and PSMRP, respectively. Mechanical properties of these two reconstruction systems, including yield and ultimate strength, fatigue strength and life, were evaluated through finite element analyses (FEA) and biomechanical tests, during which digital image correlation (DIC) was used to measure full-field displacements and strains. Results revealed that the PSMRP provides higher stiffness and longer fatigue life to the reconstruction system than the MBMRP, signified by above 33% higher stiffness in the quasi-static compression and exceeding 90% more life cycles in the cyclic test, respectively. These findings not only highlight the biomechanical advantages of PSMRP over MBMRP but also underline the strong correlation between FEA predictions and experimental outcomes in the mandibular reconstruction system, validating the FEA’s utility for preoperative biomechanical evaluation. Collectively, this work provides critical evidence supporting the biomechanical superiority of PSMRPs in mandibular reconstruction—potentially reducing risks of plate failure and reoperation—and establishes a translational framework that combines computational and experimental biomechanics to advance patient-specific implant design in oral, dental, and craniofacial surgery.

Graphical Abstract

Purpose

Pulmonary arterial hypertension (PAH) induces chronic pressure overload on the right ventricle (RV), driving remodeling, while the left ventricle (LV) remains largely preserved. The interventricular septum is often modeled as part of the LV; however, its role as a mechanically adaptive structure during PAH progression remains poorly understood. This study investigates full-thickness septal tissue mechanics in male and female rats.

Methods

RV and LV hemodynamics, septal morphology, and planar biaxial septum mechanical properties were measured in normotensive controls and rats at Weeks 4, 8, and 12 of pulmonary hypertension using the sugen-hypoxia (SuHx) rat model of PAH. Biaxial stress-strain data were fit with an exponential Fung-type constitutive model for quantitative comparison across groups.

Results

RV hemodynamics varied by both sex and disease stage, while LV hemodynamics only showed sex differences (males had larger LV volumes). Despite similar RV end-systolic pressures, septal adaptation was sex-specific. Septal tissues exhibited nonlinear, nearly isotropic mechanical behavior. Starting from the same baseline stiffness, female septal tissues became significantly more compliant at Week 4, while male septal tissues remained unchanged. By Week 8, the females returned to baseline stiffness, while the males hit their peak compliance. By Week 12, male and female septa converged to similar stiffnesses.

Conclusion

Septal mechanical properties adapt during RV pressure overload, becoming more compliant with advancing RV remodeling. The degree and timing of remodeling are sex- and disease stage-dependent. These distinct patterns suggest septal mechanics play a functional role in modulating RV-LV interaction and support the need to treat the septum as an independent structure contributing to both chambers.

Purpose

This study proposes a novel algorithm framework for optical coherence tomography (OCT) and carotid angiography co-registration (cACR), aiming to improve diagnostic precision and treatment planning for carotid artery disease.

Methods

The OCT-cACR algorithm integrates an enhanced U-Net segmentation model and a marker detection algorithm for segmenting target carotid vessels and detecting OCT probe markers. Based on the segmented target region, the You Only Look Once (YOLO) algorithm is further utilized to detect and track the OCT probe marker. The acquisition time point of each frame served as the matching parameter to achieve registration between the two modalities. Following registration, an expert compared the identified marker position on each angiography frame with its corresponding actual location to measure the resulting geographical error. The accuracy of cACR was validated using four real clinical cases, with a geographical error of less than 0.35 mm as the evaluation criterion.

Results

The segmentation model achieved higher accuracy (Dice coefficient: 0.867 ± 0.166) compared to baseline U-Net models. OCT-cACR demonstrated an accuracy of 93.33 to 100% in four test cases, thus achieving precise alignment of angiography and OCT images.

Conclusion

The proposed cACR approach is feasible and accurate and may serve as a promising tool for improving the diagnosis and treatment of carotid artery diseases.

This study combines optogenetics and retrograde transfection techniques to functionally target external urethral sphincter (EUS)-related neurons in the spinal cord and to demonstrate a proof-of-concept approach for modulating EUS activation, thereby influencing micturition. Experiments were conducted using C57BL/6 mice, in which an AAV vector (AAV2/6-eSyn-hChR2(H134R)-EGFP) was delivered to the EUS muscle, enabling retrograde transport and subsequent expression of light-sensitive proteins in motor neuron cell bodies within the spinal cord. Electromyography (EMG) of the EUS muscle in response to spinal cord photostimulation was then analyzed using fiber optics, showing that the muscle could maintain electrical activity for up to 60 s during illumination under our stimulation conditions. Finally, the real-time effects of spinal cord photostimulation on micturition were assessed via cystometry. When the bladder was sufficiently filled, 60 s of spinal cord stimulation extended continence time in proportion to the stimulation period (from 45 ± 8 s to 101 ± 14 s). These findings demonstrate that retrograde transfection from peripheral muscle to spinal motor neurons enables expression of light-sensitive proteins and allows optogenetic activation of neurons associated with the EUS. Moreover, fiber-optic stimulation effectively modulated EUS activity and micturition in situ. This electroceutical approach provides a proof-of-concept framework that may inform future strategies for treating urinary disorders and for investigating neural circuit function.

Purpose

Borderline left ventricle (BLV) presents a dilemma between pursuing a biventricular repair (BiVR) and a Stage 1 palliation (S1P) because a discordant pursuit of BiVR increases mortality risk. We aim to develop and validate a personalized computational model to assist surgical decision-making by predicting virtual surgery hemodynamics in BLV patients.

Methods

We developed a novel multi-block lumped parameter network (LPN) model of a BLV circulatory system. Patient-specific model parameters were estimated using a semi-automatic tuning framework to fit clinical data in ten retrospectively identified BLV patients. Virtual surgeries (BiVR and S1P) were performed on each patient to quantify post-operative hemodynamics.

Results

In patients who clinically received S1P (Group I, N = 5), a virtual BiVR predicted significantly elevated mean pulmonary artery pressure (PAP_mean: 38.00 ± 10.0 vs. 17.50 ± 2.7 mmHg, p < 0.01), mean left atrial pressure (LAP_mean: 25.40 ± 8.2 vs. 6.20 ± 1.2 mmHg, p < 0.0001), and single-ventricle end-diastolic pressure (SVEDP: 21.80 ± 8.7 vs. 4.80 ± 1.3 mmHg, p < 0.0001) compared with a virtual S1P. A virtual BiVR in patients who clinically underwent BiVR (Group II, N = 5) did not predict any adverse hemodynamic outcome.

Conclusion

A novel subject-specific computational modeling framework was developed to predict hemodynamics following virtual surgeries in BLV patients. The model predictions align with the clinically adopted procedure in this retrospectively selected cohort by predicting unacceptable PAP, LAP, and SVEDP. This predictive tool may guide surgeons in determining the hemodynamically optimal surgery for BLV infants, but it needs prospective validation on a larger cohort.

Central Message

Patient-specific computational modeling can predict hemodynamics following virtual surgery in borderline left ventricles and may assist surgical decision-making.

Perspective

A critical dilemma pediatric heart surgeons and pediatric cardiologists face is choosing between biventricular repair and single-ventricle palliation in patients born with a borderline left ventricle. Computational modeling using lumped parameter networks predicts hemodynamics from virtual surgery simulations and may enable clinicians to decide on the hemodynamically optimal procedure.

Purpose

Changes in residual limb volume and shape pose significant challenges in achieving and maintaining an accurate and comfortable fit for prosthetic socket. While numerous techniques for measuring residual limb volume have been proposed, their clinical application remains limited by insufficient resolution and the inability to perform in-socket measurements. To address this issue, this study develops a novel method for predicting residual limb soft tissue deformation to guide prosthetic socket design.

Methods

A three-dimensional (3D) finite element (FE) model of the human thigh was developed to simulate the soft tissue deformation during daily activities, driven by muscle contraction to replicate natural biomechanics. The model included hard tissue and muscle components, with the muscle modeled as a structure of evenly distributed, contractile fibers that generate movement. Parameters controlling fiber contraction were iteratively adjusted to best match the calculated tissue deformation and that observed in physical muscle models.

Results

The optimized FE model significantly improved the accuracy of predicting dynamic soft tissue deformation, with average errors of 0.83% and 1.86% for tissue expansion and contraction regions, respectively. For various gait patterns, the average differences in equivalent volume and cross-sectional area changes were also less than 0.83% and 1.86%, respectively.

Conclusion

The model demonstrated consistent prediction accuracy across different gait data. The fiber-driven soft tissue model developed offers a valuable tool for pre-design simulations of prosthetic sockets and orthoses. It is equally applicable to other wearable devices that interface with the skin, providing a robust framework for improving device design and functionality.