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Finite element-based feasibility study on utilizing heat flux sensors for early detection of vascular graft infections.

ABSTRACT: Aortic vascular graft infections have high morbidity and mortality rate, however, patients often do not show symptoms. Continuous implant surface monitoring will allow for early detection of infections on implant surfaces, which allows for antibiotic treatment prior to biofilm formation. We explore the possibility of using heat flux sensors mounted on an aortic vascular graft to sense the localized heat production at the onset of infectious growth. We apply Finite Element Model simulations to demonstrate changes of the heat transfer coefficient depending on different pulsatile flow parameters. We determine various differences, the main influence being the distance travelled from the inlet of the simulation with the highest heat transfer coefficient closest to the inlet and decreasing along the direction of travel of the fluid. The determined range of heat transfer coefficients of 200 to 4800 W/m² was applied to a second simulation of the thermal environment of the implant. We determined the heat transfer efficiency of the aortic graft system depending on different graft materials and thicknesses. We are further able to determine that the early detection of infection is possible by comparing the simulated amount of heat flux produced locally with the resolution of a commercial heat flux sensor.

SUBMITTER: Vehusheia SLK

PROVIDER: S-EPMC10533875 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature

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Finite element-based feasibility study on utilizing heat flux sensors for early detection of vascular graft infections.

Vehusheia Signe Lin Kuei SLK Roman Cosmin C Sonderegger Rafael R Cesarovic Nikola N Hierold Christofer C

Scientific reports 20230927 1

Aortic vascular graft infections have high morbidity and mortality rate, however, patients often do not show symptoms. Continuous implant surface monitoring will allow for early detection of infections on implant surfaces, which allows for antibiotic treatment prior to biofilm formation. We explore the possibility of using heat flux sensors mounted on an aortic vascular graft to sense the localized heat production at the onset of infectious growth. We apply Finite Element Model simulations to de ...[more]

PMID: 37758769

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Project description:Finite Element (FE) models of brain mechanics have improved our understanding of the brain response to rapid mechanical loads that produce traumatic brain injuries. However, these models have rarely incorporated vasculature, which limits their ability to predict the response of vessels to head impacts. To address this shortcoming, here we used high-resolution MRI scans to map the venous system anatomy at a submillimetre resolution. We then used this map to develop an FE model of veins and incorporated it in an anatomically detailed FE model of the brain. The model prediction of brain displacement at different locations was compared to controlled experiments on post-mortem human subject heads, yielding over 3,100 displacement curve comparisons, which showed fair to excellent correlation between them. We then used the model to predict the distribution of axial strains and strain rates in the veins of a rugby player who had small blood deposits in his white matter, known as microbleeds, after sustaining a head collision. We hypothesised that the distribution of axial strain and strain rate in veins can predict the pattern of microbleeds. We reconstructed the head collision using video footage and multi-body dynamics modelling and used the predicted head accelerations to load the FE model of vascular injury. The model predicted large axial strains in veins where microbleeds were detected. A region of interest analysis using white matter tracts showed that the tract group with microbleeds had 95th percentile peak axial strain and strain rate of 0.197 and 64.9 s-1 respectively, which were significantly larger than those of the group of tracts without microbleeds (0.163 and 57.0 s-1). This study does not derive a threshold for the onset of microbleeds as it investigated a single case, but it provides evidence for a link between strain and strain rate applied to veins during head impacts and structural damage and allows for future work to generate threshold values. Moreover, our results suggest that the FE model has the potential to be used to predict intracranial vascular injuries after TBI, providing a more objective tool for TBI assessment and improving protection against it.

Project description:BackgroundFree vascularized fibula graft (FVFG) techniques have most consistently demonstrated beneficial effects in young patients diagnosed with nontraumatic osteonecrosis of the femoral head (NONFH), and the core track technique (CTT) in particular is the most commonly used technique. As an alternative to CTT, the modified light bulb technique (LBT) has been reported to have a higher success rate. However, its biomechanical outcomes are poorly understood. This study aimed to compare the biomechanical properties of modified LBT with those of CTT in treating NONFH.MethodsTwo types (C1 and C2) of NONFH finite element models were established on the basis of a healthy subject and the Japanese Investigation Committee (JIC) classification system, and the CTT and LBT procedures were simulated in each type of model. The average von Mises stresses and stiffness of the proximal femur were calculated by applying a load of 250% of the body weight on the femoral head to simulate walking conditions. In addition, two patient-specific models were built and simulated under the same boundary conditions to further validate the LBT.ResultsIn the healthy subject-derived models, both the LBT and CTT resulted in reduced stresses in the weight-bearing area, central femoral head, femoral neck, and trochanteric and subtrochanteric regions and increased structural stiffness after surgery. In the weight-bearing area, the CTT reduced the stress more than the LBT did (36.19% vs 31.45%) for type C1 NONFH and less than the LBT did (23.63% vs 26.76%) for type C2 NONFH. In the patient-specific models, the stiffness and stresses also increased and decreased, respectively, from before to after surgery, which is consistent with the results of healthy subject-derived models.ConclusionThe biomechanical effects of the LBT and CTT differ by the JIC type of NONFH. In terms of preventing the collapse of the femoral head, the LBT may be more effective for JIC type C2 NONFH and may be a suitable alternative to the CTT, while for JIC type C1 NONFH, the CTT is still a better choice. Both techniques can improve the biomechanical properties of NONFH by reducing the proximal femoral stress and increasing the structural stiffness.

Project description:PurposeThe study presents an averaged anterior eye geometry model combined with a localised material model that is straightforward, appropriate and amenable for implementation in finite element (FE) modelling.MethodsBoth right and left eye profile data of 118 subjects (63 females and 55 males) aged 22-67 years (38.5 ± 7.6) were used to build an averaged geometry model. Parametric representation of the averaged geometry model was achieved through two polynomials dividing the eye into three smoothly connected volumes. This study utilised the collagen microstructure x-ray data of 6 ex-vivo healthy human eyes, 3 right eyes and 3 left eyes in pairs from 3 donors, 1 male and 2 females aged between 60 and 80 years, to build a localised element-specific material model for the eye.ResultsFitting the cornea and the posterior sclera sections to a 5th-order Zernike polynomial resulted in 21 coefficients. The averaged anterior eye geometry model recorded a limbus tangent angle of 37° at a radius of 6.6 mm from the corneal apex. In terms of material models, the difference between the stresses generated in the inflation simulation up to 15 mmHg in the ring-segmented material model and localised element-specific material model were significantly different (p < 0.001) with the ring-segmented material model recording average Von-Mises stress 0.0168 ± 0.0046 MPa and the localised element-specific material model recording average Von-Mises stress 0.0144 ± 0.0025 MPa.ConclusionsThe study illustrates an averaged geometry model of the anterior human eye that is easy to generate through two parametric equations. This model is combined with a localised material model that can be used either parametrically through a Zernike fitted polynomial or non-parametrically as a function of the azimuth angle and the elevation angle of the eye globe. Both averaged geometry and localised material models were built in a way that makes them easy to implement in FE analysis without additional computation cost compared to the limbal discontinuity so-called idealised eye geometry model or ring-segmented material model.

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Finite element-based feasibility study on utilizing heat flux sensors for early detection of vascular graft infections.

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Finite element-based feasibility study on utilizing heat flux sensors for early detection of vascular graft infections.

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