Simulation of tumor ablation in hyperthermia cancer treatment: A parametric study

A holistic simulation framework is established on magnetic hyperthermia modeling to solve the treatment process of tumor, which is surrounded by a healthy tissue block. The interstitial tissue fluid, MNP distribution, temperature profile, and nanofluids are involved in the simulation. Study evaluates the cancer treatment efficacy by cumulative-equivalent-minutes-at-43 centigrade (CEM43), a widely accepted thermal dose coming from the cell death curve. Results are separated into the conditions of with or without gravity effect in the computational domain, where two baseline case are investigated and compared. An optimal treatment time 46.55 min happens in the baseline case without gravity, but the situation deteriorates with gravity effect where the time for totally killing tumor cells prolongs 36.11% and meanwhile causing 21.32% ablation in healthy tissue. For the cases without gravity, parameter study of Lewis number and Heat source number are conducted and the variation of optimal treatment time are both fitting to the inverse functions. For the case considering the gravity, parameters Buoyancy ratio and Darcy ratio are investigated and their influence on totally killing tumor cells and the injury on healthy tissue are matching with the parabolic functions. The results are beneficial to the prediction of various conditions, and provides useful guide to the magnetic hyperthermia treatment

Modelling floppy iris syndrome and the impact of pupil size and ring devices on iris displacement

INTRODUCTION:The aim of this paper was to further develop a previously described finite element model which equates clinical iris billowing movements with mechanical buckling behaviour, simulating floppy iris syndrome. We wished to evaluate the impact of pupil dilation and mechanical devices on normal iris and floppy iris models. METHODS:Theoretical mathematical modelling and computer simulations were used to assess billowing/buckling patterns of the iris under loading pressures for the undilated and dilated normal iris, the undilated and dilated floppy iris, and additionally with a mechanical ring device. RESULTS:For the normal iris, billowing/buckling occurred at a critical pressure of 19.92 mmHg for 5 mm pupil size, which increased to 28.00 mmHg (40.56%) with a 7 mm pupil. The Malyugin ring device significantly increased critical initiating buckling pressures in the normal iris scenario, to 34.58 mmHg (73.59%) for 7 mm ring with boundary conditions I (BC I) and 34.51 mmHg (73.24%) with BC II. For the most floppy iris modelling (40% degradation), initiating buckling value was 18.04 mmHg (-9.44%), which increased to 28.39 mmHg (42.52%) with the 7 mm ring. These results were much greater than for normal undilated iris without restrictive mechanical expansion (19.92 mmHg). CONCLUSION:This simulation demonstrates that pupil expansion devices inhibit iris billowing even in the setting of floppy iris syndrome. Our work also provides a model to further investigate the impact of pupil size or pharmacological interventions on anterior segment conditions affected by iris position

Fluid-structure interaction in phaco-emulsification based cataract surgery

Cataract scatters the light as it enters the eye, blurs images and severely interferes people's daily activities. The only effective therapy is cataract surgery, in which the clouded lens is phacoemulsified and removed. However, an aberrant iris distortion, namely intra-operative floppy iris syndrome (IFIS), is not uncommon in the phacoemulsification process, and it greatly degrades the surgical outcomes. Despite its great impact, the mechanism of IFIS has seldom been explored from the mechanics viewpoint. This study constitutes the first exploration into IFIS mechanism within the torsional-irrigation/aspiration (T-I/A) combined mode, from the perspective of fluid-structure coupling, employing our newly developed fluid-structure interaction (FSI) simulation framework. The impacts of several factors, including probe type and position, irrigation and aspiration (I/A), iris stiffness and lens presence, are evaluated in two different torsional-irrigation/aspiration (T-I/A) combined configurations, corresponding to the scenarios of coaxial and bimanual I/A operations. Results reveal that by altering the probe's location in anterior chamber, three distinct modes of iris dynamics are recognized and defined as repulsion (RP), attraction (AT), and adhesion (AH) modes according to the relative iris-probe location. Among them, RP mode, where the iris is repelled by the probe, is preferred to ensure the safety of the iris. Furthermore, IFIS could be alleviated by stiffening iris, reducing I/A strength and choosing coaxial I/A device. These interventions result in the contraction of the damaging AH zone towards the iris root, occurring at approximately one-fourth (coaxial case), one-fifth (coaxial case), and one-fourth of the iris length, achieved by quadrupling iris stiffness, ceasing I/A flow, and utilizing coaxial I/A device, respectively. However, the risk of IFIS is only marginally impacted by the lens presence. Our findings gain a deeper insight into the iris dynamics in T-I/A mode from fluid-iris interaction viewpoint, which may provide valuable guidance for the surgical protocol operation

State-of-the-Art on Theories and Applications of Cable-Driven Parallel Robots

International audienceA cable-driven parallel robot (CDPR) is a type of high-performance robot that integrates cable-driven kinematic chains and parallel mechanism theory. It inherits the high dynamics and heavy load capacities of the parallel mechanism and significantly improves the workspace, cost, and energy efficiency simultaneously. As a result, CDPRs have irreplaceable positions in industrial and technological fields, such as astronomy, aerospace, logistics, simulators, and rehabilitation. CDPRs follow the cutting-edge trend of rigid-flexible fusion, reflect advanced lightweight design concepts, and have become a frontier topic in robotics research. This paper summarizes the kernel theories and developments of CDPRs, covering configuration design, cable-force distribution, workspace and stiffness, performance evaluation, optimization, and motion control. Kinematic modeling, workspace analysis, and cable-force solution are illustrated. Stiffness and dynamic modeling and analysis methods are discussed. To further promote the development, researchers should strengthen the investigation in configuration innovation, rapid calculation of workspace, performance evaluation, stiffness control, and rigid-flexible coupling dynamics. In addition, engineering problems such as cable materials, reliability design, and a unified control framework require attention

Simulation of fluid-structure interaction during the phaco-emulsification stage of cataract surgery

During cataract surgery the clouded lens is broken up by phacoemulsification. The iris can become highly mobile and could be entrained by the phacoemulsification probe, under a condition known as intraoperative floppy iris syndrome (IFIS). In this study we explore the mechanism of IFIS during phacoemulsification-based cataract surgery using fluid-structure interaction (FSI) simulations. As the first study of its kind, we developed a simplified two-dimensional simulation framework and utilized it to elucidate the dynamics of the iris and surrounding aqueous humor during phaco-emulsification. Three types of iris dynamics were observed when the phaco probe was operated in the torsional vibration mode and placed at various locations in the anterior chamber, which we termed as the repulsion (where the iris is repelled by the probe), attraction (where the iris is drawn toward the probe) and adhesion mode (where the iris is adhered to the probe at some point along its length), respectively. The anterior chamber is partitioned into different zones which exhibit each of these three modes. Furthermore, the effects of iris stiffness and length as well as the power and frequency of the probe operation were investigated. It was found that IFIS could be mitigated by increasing the iris stiffness, shortening the iris length (i.e., pupil dilation), decreasing the power of the emulsification probe, and maintaining the probe operation frequency in a range around the frequency of the iris’ fundamental bending mode. This study provides new physical insights into the dynamics of fluid-iris interaction during phaco-emulsification, which may guide clinicians to optimise their surgical protocol

A theoretical study of atmospheric pollutant NO₂ on as-doped monolayer WS₂ based on DFT method

For the relevant properties of pristine and doped (Si, P, Se, Te, As) monolayer WS2 before and after the adsorption of CO, CO2, N2, NO, NO2 and O2, density functional theory (DFT) calculations are made. Calculation results reveal that the monolayer WS2 doped with P and As atoms can be substrate materials for NO and NO2 gas sensors. However, after the subsequent CDD and ELF calculations, it is found that P-doped monolayer WS2 adsorbs NO and NO2 in a chemical way, while As-doped monolayer WS2 adsorbs NO and NO2 in a physical way. Also, the charge transfer between As-doped monolayer WS2 and NO is relatively small and not easily detected. Besides, As-doped monolayer WS2 system exhibits greater differences in optical properties (the imaginary part of reflectivity and dielectric function) before and after the adsorption of NO2 gas than before and after adsorption of NO gas. These differences in optical properties assist sensor devices in making gas adsorption-related judgments. Through the analysis of the recovery time, DOS and PDOS, As-doped monolayer WS2 is also verified to be a promising NO2 sensing material, whose recovery time is calculated to be as short as 0.169 ms at 300 K.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and Material

Development of an incoherent broadband cavity-enhanced absorption spectrometer for in situ measurements of HONO and NO2

Gaseous nitrous acid (HONO) is an important source of OH radicals in the troposphere. However, its source, especially that during daytime hours remains unclear. We present an instrument for simultaneous unambiguous measurements of HONO and NO2 with high time resolution based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS). To achieve robust performance and system stability under different environment conditions, the current IBBCEAS instrument has been developed with significant improvements in terms of efficient sampling as well as resistance against vibration and temperature change, and the IBBCEAS instrument also has low power consumption and a compact design that can be easily deployed on different platforms powered by a high-capacity lithium ion battery. The effective cavity length of the IBBCEAS was determined using the absorption of O2-O2 to account for the shortening effect caused by the mirror purge flows. The wall loss for HONO was estimated to be 2.0% via a HONO standard generator. Measurement precisions (2 σ) for HONO and NO2 are about 180 and 340ppt in 30s, respectively. A field inter-comparison was carried out at a rural suburban site in Wangdu, Hebei Province, China. The concentrations of HONO and NO2 measured by IBBCEAS were compared with a long optical path absorption photometer (LOPAP) and a NOx analyzer (Thermo Fisher Electron Model 42i), and the results showed very good agreement, with correlation coefficients (R2) of HONO and NO2 being ∼ 0.89 and ∼ 0.95, respectively; in addition, vehicle deployments were also tested to enable mobile measurements of HONO and NO2, demonstrating the promising potential of using IBBCEAS for in situ, sensitive, accurate and fast simultaneous measurements of HONO and NO2 in the future