Investigation of crystalline lens overshooting: ex vivo experiment and optomechanical simulation results.

Introduction: Crystalline lens overshooting refers to a situation in which the lens momentarily shifts too much from its typical location immediately after stopping the rotational movement of the eye globe. This movement can be observed using an optical technique called Purkinje imaging. Methods: In this work, an experimental setup was designed to reproduce this effect ex vivo using a fresh porcine eye. The sample was rotated 90° around its centroid using a high-velocity rotation stage, and the Purkinje image sequences were recorded, allowing us to quantify the overshooting effect. The numerical part of the study consisted of developing a computational model of the eye, based on the finite element method, that allowed us to understand the biomechanical behavior of the different tissues in this dynamic scenario. A 2D fluid-structure interaction model of the porcine eye globe, considering both the solid parts and humors, was created to reproduce the experimental outcomes. Results: Outputs of the simulation were analyzed using an optical simulation software package to assess whether the mechanical model behaves optically like the real ex vivo eye. The simulation predicted the experimental results by carefully adjusting the mechanical properties of the zonular fibers and the damping factor. Conclusion: This study effectively demonstrates the importance of characterizing the dynamic mechanical properties of the eye tissues to properly comprehend and predict the overshooting effect.

Complexity of crystalline lens wobbling investigated by means of combined mechanical and optical simulations.

Crystalline lens wobbling is a phenomenon when the lens oscillates briefly from its normal position immediately after stopping the rotational movement of the eye globe. It can be observed by means of Purkinje imaging. The aim of this research is to present the data and computation workflow that involve both biomechanical and optical simulations that can mimic this effect, aimed to better understanding of lens wobbling. The methodology described in the study allows to visualize both the dynamic changes of the lens conformation within the eye and its optical effect in terms of Purkinje performance.

FEM thermal assessment of a 3-D irregular tumor with capillaries in magnetic nanoparticle hyperthermia via dissimilar injection points.

In this study, simulation of magnetic nanoparticle hyperthermia is performed on a 3D tumor model constructed based on a CT image of a tumor. In the first step, magnetic nanoparticles are injected into two points of the tumor tissue with the same parameters. Results show that temperature profiles in the vicinity of the injection points are not similar due to the presence of blood capillaries. Therefore, the effects of using dissimilar injection parameters for the two injection points on the heating pattern and damage fraction of the tumor are investigated. The results demonstrate that using dissimilar values for injection parameters such as injection rate, injection time, and nanofluid volume fraction is a way to achieve a higher damage fraction of the tumor cells, but, the asynchronous injections strategy does not lead to more significant damage to the tumor. None of the cases showed significant improvement in the uniformity of the temperature distribution, suggesting that conducting injections under the same conditions is the best way to create an almost uniform temperature profile. The numerical simulation validation results also advocate the accuracy of the model used in this study. This research can serve as a guide for designing parameters for future studies.

Simulation of heat transfer, mass transfer and tissue damage in magnetic nanoparticle hyperthermia with blood vessels.

Numerical simulation of magnetic nanoparticle hyperthermia for cancer treatment has been investigated in this study. The presented simulation did account for the effects of fluid flow, mass flow, and heat transfer during the MNP hyperthermia. The tumor was assumed to be a porous slab, 30% of which had been necrosed previously, with two capillaries, where magnetic nanoparticles were added into the bloodstream and distributed in the tumor by blood flow through capillaries. Fluid flow, mass transfer by capillaries, and interstitial tissues have been coupled in this study. Furthermore, tumor tissue damage has been calculated using a thermal damage indicator. The goal of this research is to find an optimum injection duration and exposure time in order to maximize hyperthermia treatment effectiveness using the BOBYQA optimization method. At the end of the 1-h time hyperthermia treatment, most of the non-necrotic tissue of the tumor were damaged. Moreover, the fraction of damaged tissue increased to more than 90% in some parts of the tumor. Results of this study indicate that MNP hyperthermia with the proposed setup can effectively damage the tumor in just one session, making it more susceptible to complementary therapies such as radiotherapy or chemotherapy.