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Monitoring dynamic collagen reorganization during skin stretching with fast polarization-resolved SHG imaging
摘要： The mechanical properties of biological tissues are strongly correlated to the specific distribution of their collagen fibers. Monitoring the dynamic reorganization of the collagen network during mechanical stretching is however a technical challenge because it requires mapping orientation of collagen fibers in a thick and deforming sample. In this work, a fast polarization-resolved SHG microscope is implemented to map collagen orientation during mechanical assays. This system is based on line-to-line switching of polarization using an electro-optical modulator and works in epidetection geometry. After proper calibration, it successfully highlights the collagen dynamic alignment along the traction direction in ex vivo murine skin dermis. This microstructure reorganization is quantified by the entropy of the collagen orientation distribution as a function of the stretch ratio. It exhibits a linear behavior, whose slope is measured with a good accuracy. This approach can be generalized to probe a variety of dynamic processes in thick tissues.
关键词： biomechanics,multiphoton microscopy,skin,polarization,collagen
更新于2025-09-23 15:23:52
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Imaging and Biomechanics
摘要： Over the past 3 decades, our ability to noninvasively image structures of the musculoskeletal system has facilitated clinical diagnoses and provided insight into the success of various therapeutic interventions. As imaging modalities are refined and novel approaches are introduced, imaging technologies can provide objective measures to better understand the natural history and mechanisms of diseases and optimize and evaluate their treatment. While traditional radiography and computed tomography are commonly used to evaluate the integrity of bony structures, recent advances include biplanar videoradiography, which can now be used to directly track 3-dimensional joint motion in vivo with a high degree of accuracy.11 As such, biplanar videoradiography has been applied to study the progression of arthrosis after anterior cruciate ligament (ACL) injury.4 Based on recent technological advances, ultrasound is now being used to measure cartilage thickness to study the progression of arthrosis in vivo after ACL injury.8 Likewise, there has been a real boon in the use of magnetic resonance imaging (MRI) to evaluate anatomic, biomechanical, and compositional interactions among the structures of an injured joint. For example, MRI has been used to evaluate compositional changes of the articular cartilage in the injured joint in relation to changes in loading during gait.13 These kinds of studies provide opportunities to better understand mechanisms of posttraumatic osteoarthritis following joint injury. Furthermore, MRI has been recently applied to gain insight into the mechanisms of ACL injury.9 By using the projections of the bone bruises that occurred during ligament rupture onto the articular surfaces within the 2 compartments of the knee via models derived from 3-dimensional MRI scans, the position of the tibia relative to the femur at the time of injury can be determined.9 MRI has also been used to evaluate the structural and mechanical integrity of the menisci3 and ACL grafts after surgery.1
关键词： biomechanics,knee,MRI,imaging
更新于2025-09-23 15:23:52
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Comparison of the posterior corneal elevation and biomechanics after SMILE and LASEK for myopia: a short- and long-term observation
摘要： Purpose This study compares the posterior corneal elevation and corneal biomechanics after small incision lenticule extraction (SMILE) and laser-assisted subepithelial keratomileusis (LASEK) for myopia correction in a short- and long-term observation. Methods This prospective study included 32 patients in the SMILE group and 32 patients in the LASEK group. Corneal posterior central elevation (PCE), posterior mean elevation (PME), corneal back power (Kb), and anterior chamber depth (ACD) were evaluated with Pentacam, and intraocular pressure (IOP), corneal hysteresis (CH), and corneal resistance factor (CRF) were evaluated with the ORA at pre-operation and 3 months and 3 years post-operation. Results Three months post-operatively, CH, CRF, and IOP decreased significantly and central posterior surface shifted backward in both groups (p < 0.05). CH was lower in the LASEK group (p = 0.03) and change of CH and CRF per unit corneal tissue removed (ΔCH/ablation depth (AD) and ΔCRF/AD) was lower in SMILE than in LASEK (p = 0.01, 0.03). Three years post-operatively, the PME shifted more posteriorly in LASEK (p = 0.04), but was stable in SMILE (p = 0.06). Kb flattened and ACD was shallower in both groups (compared to preoperative data, p < 0.001). CH in the LASEK group increased and is comparable to that in the SMILE group at 3 years post-operative. Conclusion Both SMILE and LASEK can change the posterior surface and corneal biomechanics. SMILE may have less influence on corneal biomechanics than LASEK at an early stage post-operative in terms of per unit corneal tissue removed, but the effect became comparable in a long-term observation.
关键词： Corneal biomechanics,Corneal posterior elevation,Small incision lenticule extraction,Laser-assisted subepithelial keratomileusis
更新于2025-09-23 15:22:29
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Recent developments in keratoconus diagnosis
摘要： Introduction: Keratoconus and ectatic corneal diseases represent a hot area of research. The need to enhance diagnosis in order to recognize milder forms of the disease and identify inherent predisposition for ectasia progression has gained significant importance because of refractive surgery and also due to the development of new treatment modalities to treat ectatic corneal diseases. This article discusses the nomenclature related to the diagnostic tests used to characterize keratoconus and ectatic corneal diseases, providing a prospective discussion on the latest developments for the diagnosis and follow up of these conditions, including imaging modalities, biomechanical assessments, and an outlook in genetics and molecular biology. Areas covered: We performed an extensive Pubmed literature search, considering the latest developments in the diagnosis of keratoconus and additional ectatic corneal diseases. Expert Commentary: Corneal ectasia is characterized by biomechanical failure and stromal thinning, causing corneal bulging with subsequent visual impairment due to irregular astigmatism. Moderate and advanced stages are easily recognized, but the identification of mild or subclinical forms remains a challenge. Keratoconus is the most common ectatic corneal disease, being a bilateral, typically asymmetric and progressive corneal dystrophy. Corneal ectasia may occur unilaterally due to the impact from the environment, such as eye rubbing. The advent of refractive surgery and the development of new treatment modalities augmented the need for the diagnosis of milder forms of ectatic corneal disease and to document ectasia progression. Placido disc based corneal topography is sensitive to detect mild ectatic patterns in patients with relatively normal DCVA and biomicroscopy. However, the limitations of this technology are realized by the occurrence of post-refractive keratectasia despite normal anterior curvature maps and cases with suspicious topographic patterns that proceeded with LCV, based on advanced corneal imaging, resulting in documented stable outcomes. Corneal tomography, biomechanical assessment, and ocular wavefront analysis are among the diagnostic tools that enhance our ability to diagnose milder stages of keratoconus, or, even, to characterize ectasia susceptibility. Artificial intelligence and machine learning algorithms have been successful to integrate data and develop novel more accurate indices with enhanced sensitivity and specificity. This article discusses the latest developments in the diagnosis of keratoconus, including imaging modalities, biomechanical assessments, and an outlook in genetics and molecular biology.
关键词： ectasia,tomography,biomechanics,keratoconus,topography
更新于2025-09-23 15:19:57
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Riboflavin/ultraviolet A-induced collagen cross-linking in rabbit corneal scar
摘要： ● AIM: To evaluate the biomechanical stability of the corneal scar treating with riboflavin and ultraviolet A (UVA). ● METHODS: Totally 86 New Zeal rabbits were divided into control group (group A, n=8) and trauma groups [group B (n=27), group C (n=24) and group D (n=27)]. Then groups B, C and D were divided into three sub-groups according to the time points of sacrifice, i.e. groups Ba, Ca and Da (4wk, n=8); Bb, Cb and Db (6wk, n=8); Bc (n=11), Cc (n=8) and Dc (8wk, n=11). The right corneas of these 78 rabbits in the trauma groups were penetrated. Group B were only sutured. Group C were treated with corneal cross-linking (CXL) immediately after suturing. Group D were treated with CXL seven days after suturing. The corneal scar strips of 4.0×10.0 mm2 were cut and the stress and Young’s modulus at 10% strain were evaluated. Samples from the three rabbits of group Bc and three of group Dc were used to measure the expression of alpha smooth muscle action (α-SMA). ● RESULTS: The mechanical strength of the corneal scar increased with time, and was strongest at 8wk after the injury. The ultimate stress of corneal scar (group D) were 2.17±0.52 MPa, 2.92±0.63 MPa, and 4.21±0.68 Mpa at 4wk, 6wk and 8wk, respectively; Young’s modulus were 10.94±1.57 MPa, 11.16±2.50 MPa, and 13.36±2.10 Mpa, which were higher than that of other groups except for normal control. The expression of α-SMA in group B and group D were 0.28±0.11 and 0.65±0.20, respectively, and the difference was statistically significant (P=0.048). ● CONCLUSION: CXL with riboflavin/UVA at seven days after suturing improved the biomechanical properties of corneal scars most effectively in the present study.
关键词： corneal penetrating injury,biomechanics,crosslinking,cornea,rabbit
更新于2025-09-19 17:15:36
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Fiberoptic microindentation technique for early osteoarthritis diagnosis: an in vitro study on human cartilage
摘要： In this study, the capability of a fiber optic microindenter sensor to discriminate between healthy and slightly degenerated human articular cartilage samples is demonstrated. The purely optical indenter sensor is characterized by extremely reduced dimensions (0.125 mm in diameter and 27 mm in length) in comparison to existing indenter probes offering advantages for endoscopic deployment. The indenter sensor is intended to assist the surgeon in the identification of damaged articular cartilage. From each of seven specimens of human tibia plateau three samples showing different Outerbridge grading were extracted. On each sample stress-relaxation measurements were performed with eight indentation steps, each step being 40 μm and the relaxation of the material was observed for 240 s after each step. A viscoelastic model was used to fit the relaxation and to extract the characteristic parameters according to the model. A highly significant difference in stiffness (p value <0.01) was observed between the native (grade 0) and early diseased (grade 1) human cartilage samples demonstrating the potential of the fiber optic indenter for the diagnosis of cartilage breakdown.
关键词： Cartilage biomechanics,Indentation,Fiber Bragg grating,Osteoarthritis
更新于2025-09-19 17:15:36
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Dynamic Scheimpflug Ocular Biomechanical Parameters in Healthy and Medically Controlled Glaucoma Eyes
摘要： To evaluate the relationship between biomechanical parameters measured with a dynamic Scheimpflug analyzer and glaucoma. Cross-sectional observational data of 47 eyes of 47 consecutive subjects with medically controlled primary open-angle glaucoma and 75 eyes of 75 healthy subjects examined with a dynamic Scheimpflug analyzer (Corvis ST) were retrospectively investigated. Eight biomechanical parameters were compared between eyes with and without glaucoma using multivariable models adjusting for intraocular pressure (IOP), central corneal thickness, age, and axial length. In multivariable models, glaucoma was negatively correlated with A1 time (P < 0.001, coefficient = ?0.5535), A2 time (P = 0.008, coefficient = ?0.1509), radius (P = 0.011, coefficient = ?0.4034), and whole eye movement (P < 0.001, coefficient = ?0.0622). Negative correlation between glaucoma and 3 parameters (A1 time, A2 time, and radius) consistently indicate larger deformability of the cornea and negative correlation between glaucoma and whole eye movement indicate smaller eye movement, in glaucoma eyes. There were significant correlations of many biomechanical parameters with other baseline factors (8 parameters with IOP, 2 with central corneal thickness, 4 with age, and 7 with axial length). Eyes with medically controlled glaucoma were more deformable than healthy eyes, which may increase the risk of optic nerve damage through an underestimation of IOP and biomechanical vulnerability of the globe. Many parameters showed a significant correlation with baseline factors, suggesting the importance of adjustment for these confounding factors when evaluating the correlation between biomechanical parameters and ocular diseases. These results suggest the relevance of measuring biomechanical properties of glaucoma eyes for accurate IOP measurement and risk assessment.
关键词： intraocular pressure,glaucoma,cornea,biomechanics,Scheimpflug photography
更新于2025-09-12 10:27:22
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Examining stance phases with the help of infrared optical sensors in horses
摘要： The purpose of the present study was to examine the walking phases in horses using the OptoGait system, which works with optical sensors. In this pilot study, 52 healthy horses were used. For each horse, an average of 45 steps were examined. The stance phase, swing phase, step distance, and walking speeds of the horses were recorded. The stance phase of each step was examined in a separate manner in 3 steps: contact phase, foot flat, and propulsive phase. The contact phase and the propulsive phase of the forelimb and hind limb were significantly different. The propulsive phase was significantly shorter in the forelimb compared to in the hind limb, and the contact phase was significantly shorter in the hind limb. The fact that the propulsive phase of the European warmblood horses used in our study was longer than that of the British and Arabian horses was significant. It is considered that this technique might be used in the diagnosis of lameness in horses in the future with the reference measurements that were created with these data obtained from healthy horses.
关键词： horse walking analysis,veterinary anatomy,Biomechanics,stance phase
更新于2025-09-11 14:15:04
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Radiology, Lasers, Nanoparticles and Prosthetics || 15. Prosthetics
摘要： When body parts and functions fail there are two possibilities for remedy: regeneration or replacement. Regeneration is always the better option. However, if by any reason this option is not available, replacement by a donor or by artificial parts is the second best choice. In this chapter we consider artificial replacements, called prostheses. Prostheses may replace limbs or organs and are supposed to take over as well as possible the function of the healthy organ. We distinguish between two types of prosthesis: Exoprosthesis, prosthesis external to the body; Endoprosthesis, prosthesis within the body, also called implants.
关键词： computer technology,electronics,implants,exoprosthesis,prostheses,biomechanics,biomedicine,endoprosthesis,materials science,bionics
更新于2025-09-11 14:15:04
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Biomechanical changes in the cornea following cataract surgery: a prospective assessment with the Corvis-ST
摘要： Importance: Intraocular pressure is often reduced following cataract surgery. Postoperative changes in corneal stiffness are likely to be at least partly responsible for any reduction in IOP measured with applanation tonometry. Background: To determine the effect of cataract surgery and corneal incision size on corneal biomechanics. Design: Prospective randomised trial Participants: One-hundred prospectively enrolled patients qualifying for cataract surgery Methods: Participants were randomised to clear corneal incisions with a 2.20 or 2.85mm keratome. Corvis-ST tonometry and dynamic corneal response measurements were obtained preoperatively, and 3-months postoperatively. Multiple regression analysis was completed using R software. Main Outcome Measures: Corvis-ST biomechanical parameters Results: Ninety-three eyes of 93 patients were included in the final analysis. Mean Corvis-ST biomechanically corrected intraocular pressure decreased by 3.63 mmHg postoperatively (95% confidence interval = 2.97 – 4.35, P ≤0.01), and central pachymetry increased by 6.96μm (4.33 – 9.59, P ≤0.01). Independent of IOP and pachymetry changes, mean (± standard error) corneal first applanation stiffness parameter reduced by 9.761±3.729 (P = 0.01) postoperatively. First applanation velocity increased by 0.007±0.002ms, second applanation velocity increased by 0.012±0.004ms (P ≤0.01), the first applanation deformation amplitude increased by 0.008±0.002mm (P ≤0.01), and the deflection amplitude at highest concavity increased by 0.030±0.069 (P ≤0.01). There were no significant differences between different incision size groups. Conclusions and Relevance: Corneal stiffness is reduced three months following cataract surgery and is associated with falsely low intraocular pressure measurements. This finding may be important for glaucoma patients and in particular when assessing the effectivity of Minimally Invasive Glaucoma Surgery devices.
关键词： Corneal biomechanics,Corvis-ST,Cataract surgery
更新于2025-09-09 09:28:46