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Thermal ablation of tumors is a minimally invasive technique more and more employed in cancer treatments. The main shortcomings of this technique are, on the one hand, the risk of an incomplete ablation, and on the other hand, the destruction of the surrounding healthy tissue. In this work, thermal ablation of a spherical hepatocellular carcinoma tumor (HCC) surrounded by healthy tissue is modeled. A modified porous media-based bioheat model is employed, including porosity variability from tumor core to healthy tissue, following experimental in vivo measures. Moreover, three different protocols are investigated: a constant heating protocol, a pulsating protocol, and a new developed damage-controlled protocol. The proposed damage-controlled protocol changes the heating source from constant to pulsating according to the thermal damage probability on the tumor rim. The equations are numerically solved by means of the commercial software COMSOL Multiphysics, and the outcomes show that the new proposed protocol is able to achieve the complete ablation in less time than the completely pulsating protocol, and to reach tissue temperature on the tumor rim 10 °C smaller than the constant protocol. These results are relevant to develop and improve different patient-based and automated protocols which can be embedded in medical devices’ software or in mobile applications, supporting medical staff with innovative technical solutions.

Studying fluid dynamics in an operating room has a key role to achieve the right air quality conditions inside, for different purposes, and thus the patient comfort, the correct air distribution (distinguishing infected or not infected patients), the recirculation of contaminants and so on. One of the most relevant parameters to take into account is the age of air, defined as the mean time that a particle takes to go from an inlet point to the considered point. This parameter can be employed to evaluate the air change effectiveness inside the room. In this study, the effect of two distinct arrangements of recovery grids for the air outflow and two different positions of the lighting systems are considered. The computational fluid dynamics software ANSYS Fluent is used to solve the partial differential equations governing the mass transport, air velocity components, turbulence, energy, and age of air in order to evaluate the changes in terms of age of air and air changes effectiveness in critical zones of an octagonal operating room. Inside the room, the presence of four people of medical staff and the patient is considered too. The results show critical differences among the distinct considered arrangements, highlighting how relevant the operating room fluid dynamics is. The lowest mean age of air (136 s) and the highest air changes effectiveness (108 %) among the simulated configurations occur in the case of vertical return grids and vision lamp on patient bed and when the xy vertical plane located at the center of the room is considered

Thermal ablation has a primary role in cancer treatment due to its minimal invasiveness, and the improvement of this technique is fundamental in order to avoid incomplete ablation or healthy tissues ablation. In this work, modified bioheat models based on Pennes’ or LTNE bioheat models are employed in a simplified two-layer spherical model made up by a hepatocarcinoma tumor bounded by a healthy liver tissue. Improvements are done by including variable porosity or perfusion into either LTNE-based or Pennes-based models, accounting for local properties variations. Other modifications in common to both models, like blood flow arrest induced by necrosis, or employing an equivalent external thermal dose as the heat source term, are introduced too. Numerical results are presented in terms of temperature fields, thermal damage evolution, and the resulting ablation size. The latter, that represent the main outcome from a thermal ablation procedure, is compared with experimental measurements performed on an in vivo clinical study referred to hepatocellular carcinomas in human beings. From these comparisons, it is shown that the modified porous media-based model provides a very good agreement, with lesion sizes differences which are no higher than 9.1%; on the other hand, the modified Pennes’ equation allows to a slight underestimation of the achieved temperatures due to a too much high heat sink effect. The information derived from the present study would be very helpful to improve thermal ablation modeling by employing a LTNE bioheat porous model that accounts for aspects like variable porosity and other model improvements.

In this work, two different bioheat models are implemente d to model a thermal ablation of hepatocellular carcinoma liver tumor . A mixed constant and pulsating heat source protocol is developed, evaluating the thermal damage level on the tumor rim. A porous media based model and a modified Pennes’ bioheat equation are developed to consider the realistic variation of both blood volume fraction (porosity) in the first model, and perfusion term in the second one , from tumor core, tumor rim, and the sur rounding healthy tissue. The results are presented in terms of temperature fields, thermal damage and dimension of the ablated zone achieved.

Nowadays, Organic Rankine Cycle (ORC) is one of the most promising technologies analyzed for electrical power generation from low-temperature heat such as renewable energy sources (RES), especially solar energy. Because of the solar source variation throughout the day, additional Thermal Energy Storage (TES) systems can be employed to store the energy surplus saved during the daytime, in order to use it at nighttime or when meteorological conditions are adverse. In this context, latent heat stored in phase-change transition by Phase Change Materials (PCM) allows them to stock larger amounts of energy because of the larger latent energy values as compared to the specific heat capacity. In this study, a thermal analysis of a square PCM for a solar ORC is carried out, considering four different boundary conditions that refer to different situations. Furthermore, differences in including or not natural convection effects in the model are shown. Governing equations for the PCM are written with references to the heat capacity method and solved with a finite element scheme. Experimental data from literature are employed to simulate the solar source using a time-variable temperature boundary condition. Results are presented in terms of temperature profiles, stored energy, velocity fields and melting fraction, showing that natural convection effects are remarkable on the temperature values and consequently on the stored energy achieved.

Thermal ablation is a minimally or noninvasive cancer therapy technique that involves fewer complications, shorter hospital stays, and fewer costs. In this paper, a thermal-ablation bioheat model for cancer treatment is numerically investigated, using a porous media-based model. The main objective is to evaluate the effects of a variable blood volume fraction in the tumoral tissue (i.e., the porosity), in order to develop a more realistic model. A modified local thermal nonequilibrium model (LTNE) is implemented including the water content vaporization in the two phases separately and introducing the variable porosity in the domain, described by a quadratic function changing from the core to the rim of the tumoral sphere. The equations are numerically solved employing the finite-element commercial code COMSOL Multiphysics. Results are compared with the results obtained employing two uniform porosity values (ε = 0.07 and ε = 0.23) in terms of coagulation zones at the end of the heating period, maximum temperatures reached in the domain, and temperature fields and they are presented for different blood vessels. The outcomes highlight how important is to predict coagulation zones achieved in thermal ablation accurately. In this way, indeed, incomplete ablation, tumor recurrence, or healthy tissue necrosis can be avoided, and medical protocols and devices can be improved.

Background and objectives Hyperthermia treatment is nowadays recognized as the fourth additional cancer therapy technique following surgery, chemotherapy, and radiation; it is a minimally or non-invasive technique which involves fewer complications, a shorter hospital stay, and fewer costs. In this paper, pulsating heat effects on heat transfer in a tumor tissue under hyperthermia are analyzed. The objective of the paper is to find and quantify the advantages of pulsatile heat protocols under different periodical heating schemes and for different tissue morphologies. Methods The tumor tissue is modeled as a porous sphere made up of a solid phase (tissue, interstitial space, etc.) and a fluid phase (blood). A Local Thermal Non-Equilibrium (LTNE) model is employed to consider the local temperature difference between the two phases. Governing equations with the appropriate boundary conditions are solved with the finite-element code COMSOL Multiphysics®. The pulsating effect is modeled with references to a cosine function with different frequencies, and such different heating protocols are compared at equal delivered energy, i. e. different heating times at equal maximum power. Results Different tissue properties in terms of blood vessels sizes and blood volume fraction in tissue (porosity) are investigated. The results are shown in terms of tissue temperature and percentage of necrotic tissue obtained. The most powerful result achieved using a pulsating heat source instead of a constant one is the decreasing of maximum temperature in any considered case, even reaching about 30% lower maximum temperatures. Furthermore, the evaluation of tissue damage at the end of treatment shows that pulsating heat allows to necrotize the same tumoral tissue area of the non-pulsating heat source. Conclusions Modeling pulsating heat protocols in thermal ablation under different periodical heating schemes and considering different tissues morphologies in a tumor tissue highlights how the application of pulsating heat sources allows to avoid high temperature peaks, and simultaneously to ablate the same tumoral area obtained with a non-pulsating heat source. This is a powerful result to improve medical protocols and devices in thermal ablation of tumors.

The relevance of thermal ablation in cancer treatment is growing through the years, because it involves fewer complications, a shorter hospital stays, and less costs. In this article, the effects of different antennas configurations in thermal ablation are investigated. Single, double, and triple antennas configurations are modeled in order to simulate the hepatic cancer treatment, which often requires the destruction of large volume lesions. The tissue is modeled as a porous domain made up by a solid phase (cells and interstitial spaces) and a fluid phase (blood). The generic heat sources are referred only to a part of this domain, and they supply equal total power and energy for the different configurations. A Local Thermal Non-Equilibrium (LTNE) model is employed, modified in order to include two-phase water vaporization (tissue and blood). Two different blood volume fractions in liver were considered and four different blood velocity were modeled. Governing equations with the appropriate boundary conditions are solved with the finite-element code COMSOL Multiphysics®. Results are presented in terms of temperature fields and tissue damage for the three different configurations and they show how using multiple antennas offers a potential solution for creating ablation zones with larger dimensions.

One of the most used cancer treatments is the thermal ablation, in which necrosis in tumor tissues is induced by employing a certain thermal dose. Depending on the lesion and other medical aspects, a prefixed thermal dose is applied by varying thermal power and/or exposure time. Besides, it is important to apply the right thermal dose in order to not damage healthy tissues. In this paper, the effects of a pulsating heat source on a tumor cell are investigated in order to improve thermal ablation processes. The tumor cell is modelled as a porous sphere made up by a solid phase (tissue, interstitial space, etc.) and a fluid phase (blood). The pulsating heat source term is referred only to a part of this sphere. A Local Thermal Non-Equilibrium (LTNE) model is employed to take into account the local temperature difference between the two phases. Governing equations with the appropriate boundary conditions are solved with the finite-element code COMSOL Multiphysics®. Results are presented in terms of temperature fields and tissue damage for different pulsatile heating conditions, blood velocities and porous tissue geometrical properties, in order to show under which condition, at equal thermal dose, thermal ablation procedure is optimized.

It is quite challenging to describe heat transfer phenomena in living systems because of the involved phenomena complexity. Indeed, thermal conduction and convection in tissues, blood perfusion, heat generation due to metabolism, complex vascular structure, changing of tissue properties depending on various conditions, are some of the features that make hard to obtain an accurate knowledge of heat transfer in living systems for all the clinical situations. This theme has a key role to predict accurately the temperature distribution in tissues, especially during biomedical applications, such as hyperthermia treatment of cancer, in which tumoral cells have to be destroyed and at the same time the surrounding healthy tissue has to be preserved. Moreover, the lack of experimentation in this field, due to ethical reasons, makes bioheat models even more significant. The first simple bioheat model was developed in 1948 by Pennes (J Appl Physiol 1:93-122, 1948) but it has some shortcomings that make the equation not so accurate. For this reason, over the years it has been modified and more complex models have been developed. The purpose of this review is to give a clear overview of how the bioheat models have been modified when applied in various hyperthermia treatments of cancer.

The investigation of bioheat transfer is a difficult issue because it entails a mixture of many mechanisms to take into account, such as thermal conduction in tissues, convection and blood perfusion, metabolic heat generation, vascular structure, changing of tissue properties depending on physiological condition and so on. This topic has a key role to predict accurately the temperature distribution in tissues, especially during biomedical applications. In this paper, different bioheat transfer models are resumed and compared. The biological tissue is modelled as a porous sphere and liver tissue properties are used. Governing equations are averaged over a Representative Elementary Volume (REV) of the living tissue. Transient bioheat equations based on models like, for example, Pennes model, Local Thermal Non-Equilibrium equations (LTNE model), are employed. In the employed equations, radiative heat transfer is also considered. Governing equations with the appropriate boundary conditions are solved with the finite-element code COMSOL Multiphysics®. The effects of hyperthermia on the living tissue are included with a source term in the tissue energy equation. Results are presented in terms of temperature profiles in the biological tissue; the aim is to appreciate differences due to the various bioheat models.

Sustainability is an increasingly common and important issue in daily life, which in turn becomes an advantage when handled strategically by managers in their businesses. Nevertheless, in the Brazilian cosmetics and personal care industry one can find companies that consciously resist this trend. In this context, this article aims to highlight the advantages of using sustainability as a business strategy. The method used was a case study with a qualitative approach. In the case of the company, which was the subject of study of this work, the reasons that have led it to remain inert are strongly related to its model for running the business, especially the lack of long-term planning, a strong hierarchy, low leadership awareness and overvaluation of investors, making sustainability a seemingly incompatible matter for the organization. The studied company's own stakeholders, particularly employees, have identified several innovative opportunities for it to progress toward sustainability. However, in most cases, managers have been prevented from pursuing sustainable actions on the grounds that such initiatives are subjective and have no value.