Effects Of Blood Perfusion Research Articles

Quantitative investigation on the effects of eyeball geometry, blood perfusion and natural convection in retinal laser surgery

The photothermal effects of laser on tissue are widely used in ophthalmology to treat retinal diseases. The accurate modelling of retinal laser surgery will prove valuable guidance for clinic treatment. There are several important issues should be carefully evaluated during retinal laser surgery modelling, including the eye geometry (whole eye or fundus only, retinal pigment epithelium layer incorporated or not), blood perfusion and natural convection. In previous publications, the existence of the anterior part of eyeball and retinal pigment epithelium layer is neglected to simply the eye geometry due to low laser light absorption (anterior part of eyeball) or small volume occupation (retinal pigment epithelium layer), respectively. However, the justification of this treatment has not been conducted. In this study, we will quantitatively investigate these factors systemically in a large pulse duration range that covers all the retinal laser surgery used in clinic. To do this, we present a bioheat transfer model for the simulation of the thermal response of the eye to laser irradiation. In the simulation, the 3D whole-eye geometry is considered. The Pennes bioheat transfer equation is adopted for the whole-eye temperature modelling. Simultaneously, we treat the fundus as a multilayered medium that all primary components, including RPE layer, are considered for first time in whole eye modelling. Our model calculates the thermal responses of the eye during laser retinal surgery with the pulse duration from nanosecond to tens of second. The effects of eye geometry, blood perfusion and natural convection are clearly clarified based on the laser pulse duration and incident energy used. The results show that neglecting the anterior part of eyeball will introduce the computational error more than 27 %. The existence of the retinal pigment epithelium layer should always be considered in retinal laser surgery modelling in all pulse durations used in clinic, otherwise more than 20 % computational error will be generated. When the pulse duration is longer than 10s, the effect of blood perfusion and natural convection in vitreous body should both be considered.

Non-Fourier Bioheat Transfer Analysis in Brain Tissue During Interstitial Laser Ablation: Analysis of Multiple Influential Factors

This work presents the dual-phase lag-based non-Fourier bioheat transfer model of brain tissue subjected to interstitial laser ablation. The finite element method has been utilized to predict the brain tissue's temperature distributions and ablation volumes. A sensitivity analysis has been conducted to quantify the effect of variations in the input laser power, treatment time, laser fiber diameter, laser wavelength, and non-Fourier phase lags. Notably, in this work, the temperature-dependent thermal properties of brain tissue have been considered. The developed model has been validated by comparing the temperature obtained from the numerical and ex vivo brain tissue during interstitial laser ablation. The ex vivo brain model has been further extended to in vivo settings by incorporating the blood perfusion effects. The results of the systematic analysis highlight the importance of considering temperature-dependent thermal properties of the brain tissue, non-Fourier behavior, and microvascular perfusion effects in the computational models for accurate predictions of the treatment outcomes during interstitial laser ablation, thereby minimizing the damage to surrounding healthy tissue. The developed model and parametric analysis reported in this study would assist in a more accurate and precise prediction of the temperature distribution, thus allowing to optimize the thermal dosage during laser therapy in the brain.

The Power Setting of Focused Ultrasound for the Palliative Treatment of Advanced Pancreatic Cancer: A Study in an Ex Vivo Bovine Liver

High-intensity focused ultrasound (HIFU) ablation has been widely used in advanced pancreatic cancer in recent years. In numerous studies, HIFU has been shown to be safe, effective, and practicable, but there are a few HIFU-related adverse effects. The patients’ discomfort during therapy increased proportionally with increasing delivered energy and pain levels seemed to be independent of the dose of anesthetic or sedation. If the power used in therapy is too high, the temperature of the target area will rise rapidly, and the boiling and cavitation make the shape of the necrosis area difficult to control. In recent years, moderate-intensity focused ultrasound (MIFU) has also been shown to heat the tumor locally for palliative treatment. Choosing the appropriate power and effectively controlling the tissue temperature until reaching the threshold for thermal necrosis are of great significance for ensuring the safety of palliative treatment. In this study, an infrared temperature measurement experimental system was set up to measure the temperature rise at different power in an ex vivo bovine liver. It was found that when the acoustic intensity of the focused ultrasound was lower than the cavitation threshold (within the range of the MIFU), the temperature of the tissue kept rising at a steady rate and could still reach the thermal damage threshold temperature within tens of seconds. The results showed that the temperature induced by the MIFU was almost entirely dependent on the thermal effect, and the temperature of the tissue at the end of sonication was linearly related to the power. Finally, this study considered the effect of blood perfusion on the temperature for the application of focused ultrasound in the palliative treatment of advanced pancreatic cancer with the goal of providing a reference for the application of focused ultrasound in the palliative treatment of advanced pancreatic cancer.

Effect of Blood Perfusion on Temperature Distribution in the Multilayer of the Human Body with Interstitial Hyperthermia Treatment for Tumour Therapy

Blood perfusion is defined as the volume of blood flowing through units of tissue volume per second. In thermoregulation, blood perfusion is a factor that affects heat transfer in the body, the greater the rate of blood perfusion will complicate the distribution of temperature throughout the body. In the study of bioheat transfer, heat transfer in the human body can be used as a therapy. At therapeutic temperatures (above 40°C), cells will die and stop their growth or commonly called hyperthermia therapy. It can allow thermonecrosis in body tissues and can be useful for tumour tissue. Of the various types of hyperthermia therapy, interstitial hyperthermia therapy is considered more effective because heat is directly delivered to tumour tissue to minimize other tissues exposed to therapeutic temperatures. Currently, there are no studies that study the effect of blood perfusion on the treatment of interstitial hyperthermia, even though blood perfusion greatly affects the temperature distribution in the human body/ In this study, heat transfer analysis will be performed on five layers of the human body, namely the epidermis, dermis, fat, muscle, and bones with interstitial application of hyperthermia therapy and affected by blood perfusion with a value of (8x10-4; 4x10-4; 2x10-4; 1x10-3; and 2x10-3)/s completed using finite element method with unsteady conditions in two axial dimensions. The part of the tumour studied is a tumour in the arm (forearm) in the span of 600s. This study shows that blood perfusion affects the value of temperature distribution in five layers of the body in unsteady conditions. The greater the value of blood perfusion flowing in the body, the more difficult the temperature will be to transmit because the blood distributes heat throughout the body faster, the difference between blood perfusion values is quite significant.

Finite Difference Method Simulation on Effect of Blood Perfusion on Temperature Distribution of Female Human Skin

<p><span lang="EN-US">Bioheat</span><span lang="EN-US"> transfer is a combination of heat transfer and biology process comprising of transfer of heat from human living tissue to the environment. This study aims to estimate the temperature distribution of female human’s skin. In this study, effect of varied blood perfusions of 1.5, 2.0, 2.5 and 3.0 kg/s.m<sup>3 </sup>on bioheat transfer of female human skin, which was modeled into four layers, was simulated. To address this issue, one-dimensional unsteady state finite difference method was applied in this study. Result of this study informed that the finite difference method can be used to solve the bioheat transfer equation and to estimate temperature distribution of different skin layers of female human. In this study, blood perfusion affects temperature distribution in the four layers of unstable women's skin. The highest blood perfusion of 3 kg/s.m<sup>3</sup> resulted in more homogeny temperature distribution of different skin layers. This circumstance occurred since higher blood perfusion increases heat transfer between blood and skin layers.</span></p>

Development of a numerical multi-layer model of skin subjected to pulsed laser irradiation to optimise thermal stimulation in photorejuvenation procedure

Background and Objective: This paper presents the development of a 3D physics-based numerical model of skin capable of representing the laser-skin photo-thermal interactions occurring in skin photorejuvenation treatment procedures. The aim of this model was to provide a rational and quantitative basis to control and predict temperature distribution within the layered structure of skin. Ultimately, this mathematical and numerical modelling platform will guide the design of an automatic robotic controller to precisely regulate skin temperature at desired depths and for specific durations. Methods: The Pennes bioheat equation was used to account for heat transfer in a 3D multi-layer model of skin. The effects of blood perfusion, skin pigmentation and various convection conditions are also incorporated in the proposed model. The photo-thermal effect due to pulsed laser light on skin is computed using light diffusion theory. The physics-based constitutive model was numerically implemented using a combination of finite volume and finite difference techniques. Direct sensitivity routines were also implemented to assess the influence of constitutive parameters on temperature. A stability analysis of the numerical model was conducted. Results: Finally, the numerical model was exploited to assess its ability to predict temperature distribution and thermal damage via a multi-parametric study which accounted for a wide array of biophysical parameters such as light coefficients of absorption for individual skin layers and melanin levels (correlated with ethnicity). It was shown how critical is the link between melanin content, laser light characteristics and potential thermal damage to skin. Conclusions: The developed photo-thermal model of skin-laser interactions paves the way for the design of an automated simulation-driven photorejuvenation robot, thus alleviating the need for inconsistent and error-prone human operators.

From Micromagnetic to In Silico Modeling of Magnetic Nanodisks for Hyperthermia Applications

AbstractMagnetic nanodisks have been recently proposed as biomedical tools for therapeutics at the nanoscale level, with a special focus on hyperthermia for cancer cure. Here we present a detailed study of permalloy nanodisks to be used in alternative to superparamagnetic iron oxide nanoparticles, as efficient heating agents that release heat via magnetic hysteresis. A micromagnetic modeling analysis is carried out to identify sizes and ac field parameters that maximize the specific loss power (SLP), guaranteeing the fulfillment of biophysical constraints (Hergt–Dutz limit) and vortex state at remanence (reduced agglomeration effects). The highest SLP (790 W g−1) is found for 100 nm diameter and 20 nm thickness nanodisks, excited at a frequency of 75 kHz. Further analysis elucidates the influence of magnetostatic interactions and local nanodisk‐field orientation on the SLP of nanodisk clusters, which originate from the deposition in target tissues. At high concentrations, magnetostatic interactions can lead to a reduction of 40–50% in the hysteresis losses. From thermal simulations, we finally demonstrate that in a murine model temperature increments comparable to that obtained in calorimetric measurements under quasi‐adiabatic conditions can be achieved only by using an order of magnitude larger dosage of nanodisks, due to blood perfusion effects.

Numerical study on the effects of blood perfusion and tumor metabolism on tumor temperature for targeted hyperthermia considering a realistic geometrical model of head layers using the finite element method

The main aim of the present work is to determine the temperature distribution in the normal and cancerous tissues to achieve the desired condition of hyperthermia. Hyperthermia can be defined as the mild elevation of the temperature to 40–46 °C, which induces the cancer cell death and enhances the effects of the radiotherapy and chemotherapy. In the present research, the realistic geometry of the human head layers and the tumor are modelled, geometrically, and then simulated similar to the real samples of MRI images with the size of 5990 mm3. The temperature distribution in the tumor and healthy tissues was obtained based on the solution of Penne’s bio-heat transfer equation utilizing the Finite Element scheme. Employing the accurate boundary conditions for the thermal simulation of the problem, two main layers of the human brain, namely, white matter (WM) and gray matter (GM), as well as the cerebrospinal fluid (CSF) and the skull, are considered in the thermal analysis. In order to examine the hyperthermia conditions, the effects of the different blood perfusion rates and tumor metabolism on the tumor temperature are analyzed. The results showed that by reducing the blood perfusion rate from 0.0016 to 0.0005(ml/(ml.s)), the temperature increased by nearly 0.2 ℃ at the center of the tumor implying that the variations of the blood perfusion rate in the tumor have not a significant influence on its temperature. Moreover, it was found that when the tumor metabolism increases five times (equal to 125 × 103 W/m3) than its normal value (equal to 25,000 W/m3), the temperature reaches to the range needed for ablation of the brain tumor (40–46 ℃). The results also indicated that the manipulation of the cancer tissues metabolic rate via thermal simulation could be efficiently employed to estimate the amount of heat needed for the thermal ablation of the tumor.

Two-port network modeling for bio-heat transfers in lungs

Abstract In open-heart surgery, temperature changes may severely damage organ tissues, therefore a better knowledge of thermal transient effects is required to improve temperature control. Heat transfer in a biological context is usually treated by means of empirical relationships or simple resistance models. In some cases, fairly simplified models only involving thermal resistance R and a heat capacity C are used. More advanced models which may be accurate enough tend to rely on heavy finite element computations. An intermediate model is sought to more accurately describe transient effects. By combining the well-known Pennes’ bio-heat equation combined to a thermal two-port network, a circuit model is proposed to take into account thermal transients in a perfused tissue. A larger frequency band can be taken into account for such an approach. The proposed models may also consider the effect of blood perfusion on the temperature transients, as well as blood temperature fluctuations (as in extracorporeal circulation, for example) and metabolic heat generation. For a simple 1D scenario, sensitivities to different heat or temperature inputs are compared. The obtained impedance expressions are also analyzed for different branch levels of the lung.

Numerical analysis of local non-equilibrium heat transfer in layered spherical tissue during magnetic hyperthermia

A solid multi-layered concentric sphere with Gaussian space source is considered as the tissue model for magnetic hyperthermia treatment. The generalized dual-phase-lag model of bioheat transfer is used to describe the behavior of heat transport in tissue in the hyperthermia treatment process for accounting the local non-equilibrium effect. The effects of blood perfusion with the transient temperature are included in the tissue model. The hybrid numerical scheme based on Laplace transform, change of variables, and the modified discretization technique is extended to solve the present problem. The analytical solution for constant heat generation in the inner sphere is presented and evidences the accuracy and rationality of the present numerical results. In an ideal hyperthermia treatment, all the diseased tissues should be selectively heated without affecting any healthy tissue. Attempting to achieve the ideal temperature distribution, the thermal dose is estimated at the specified condition. The corresponding thermal efficacy of tumor damage has also been assessed based on the Arrenius equation.

Dimethyl Sulfoxide is Less Effective in Immersing Cryopreserved Large Pieces of Tissue: A Rabbit Hind-Limb Model.

BackgroundDimethyl sulfoxide (DMSO) cryoprotectant can effectively alleviate the damage to single tissue during cryopreservation and restore its physiological activity after rewarming. However, studies have not been successful for preserving large tissue. This study aimed to investigate the application conditions of DMSO in large composite-tissue by performing femoral artery perfusion and soaking in a rabbit hind-limb model.Material/MethodsA microdialysis-freezing point osmometer was used to detect the minimum time required for effective perfusion of 10% v/v perfusion and 20% v/v perfusion group. Magnetic resonance spectroscopy (MRS) was used to detect the area under the spectrum peak of DMSO in perivascular, intramuscular, subcutaneous areas, and compare the area under the spectrum peak in the 20% vascular perfusion group and other whole immersion groups.ResultsThe minimum time required for effective perfusion of muscle in the 10% v/v group was 30 minutes, the DMSO concentration was stable at 5% v/v; In the 20% v/v group the minimum time was at 20 minutes, stable at 12% v/v. There was a statistically difference of the area under the spectrum peak in the 10% group and the 20% v/v group after vascular perfusion in different tissue locations (P<0.05). The 20% vascular perfusion group and the different concentration of DMSO in the large tissue soaking group were statistically different (P<0.05). There was a significant difference in the 20% v/v vascular perfusion group compared to the low concentration immersion group, but no difference compared to the 50% immersion group.ConclusionsThe effect of blood perfusion on cryopreservation in large tissue by using DMSO was slightly better than overall soaking, especially in preservation of skin and subcutaneous tissue.

Numerical analysis of power dissipation requirement in magnetic hyperthermia problems.

Control of the therapeutic temperature is essential in performing magnetic fluid hyperthermia. Thus, reliable predictions of the power dissipation are required to determine the correct dosage of magnetic particles to be injected into the cancerous tissue prior to treatment. To meet this requirement, the present study evaluates the power dissipation requirement for two magnetic hyperthermia problems reported in the literature. There is a significant challenge for solving the bio-heat transfer model for concentric bi-layered solid spheres. Consequently, the present study employs a hybrid technique based on Laplace transformation and a modified discretization scheme to solve the considered hyperthermia problems. Analytical solutions are provided to demonstrate the validity of the proposed approach. The unreliability of the results presented in the literature is then demonstrated using the proposed numerical scheme. In general, the results presented in this study show that the power dissipation required to maintain an effective temperature range in the tumor domain is related to the rate of temperature rise, the tumor size, the blood perfusion rate, and the tissue properties. In particular, the power dissipation should be increased for the cooling effect of blood perfusion or a smaller tumor volume.

An analytical solution of the bioheat model in a spherical tissue due to laser irradiation

This article studies an analytical approach associated with Laplace transform, experimental temperature data and a sequential concept over time to obtain the thermal damage and the temperature in living tissue due to laser irradiation. The effects of blood perfusion and the thermal relaxation time on the temperature of skin tissues and the resulting of thermal damage are investigated. The resulting of thermal damage to the tissue is assessed by the denatured protein range using the formulation of Arrhenius. The outcomes show that the hyperbolic bioheat model is reduced to the parabolic bioheat model when the relaxation time is close to zero. The numerical outcomes of thermal injuries and temperatures are graphically introduced. In conclusion, the comparison between the numerical computations and the existing experimental study displays that a current mathematical model is an effective tool for evaluating the biological heat transfer in biological tissues.

Numerical study on the effects of blood perfusion and body metabolism on the temperature profile of human forearm in hyperthermia conditions.

The development of mathematical models for describing the thermal behavior of living tissues under normal or hyperthermia conditions is of increasing importance. In this research, a 3D forearm model based on anthropometric measurement of 25 samples in Tehran, Iran was developed. The tissue temperature distribution is obtained via the Finite Volume Method (FVM) by considering the appropriate boundary conditions, blood perfusion, body metabolism, and the application of hyperthermia conditions on the tissue. The Pennes Bioheat Transfer Equation (PBHTE) is considered in this regard. Also, various thermophysical properties are assumed for the model in order to clarify the effects of such parameters on the tissue temperature distribution. The results of this study indicate that it is possible to provide the desired conditions for many therapeutic processes by controlling the parameters such as blood perfusion, body metabolism and the type of external heat source applied on the tissue. Generally, by decreasing the body metabolism, increasing the blood perfusion rate in tissue and applying a fluctuating heat flux, instead of uniform heat flux on the surface of the forearm skin, it is possible to provide the hyperthermia conditions without causing damages such as burn injuries to the other parts of the tissue. By using the results of this study, the appropriate conditions of hyperthermia can be obtained.

Numerical Study of Hyper-Thermic Laser Lipolysis With 1,064 nm Nd:YAG Laser in Human Subjects.

The aim of this study was to develop a numerical model for hyperthermic laser lipolysis in human subjects to improve understanding of the procedure and find optimal therapeutic parameters. A numerical model of hyperthermic laser lipolysis (HTLL) on human subjects was developed that is based on light and heat transport, including the effects of blood perfusion and forced air cooling. Tissue damage was evaluated using the Arrhenius model. Three irradiation scenarios were considered: single skin area irradiation without and with forced air cooling, and sequential heating of four adjacent skin areas in a cyclical manner. An evaluation of the numerical model was made by comparing the recorded skin surface temperature evolution during an experimental HTLL procedure performed on the abdomen of ten human volunteers using a 1,064 nm Nd:YAG laser irradiation. A good agreement was obtained between the simulated skin surface temperatures and thatas measured during the HTLL procedure. The temperature difference between the simulations and experiments was in the range of 0.2-0.4°C. The model parameters, which were fitted to the experiment were the perfusion parameter (0.36-0.79 and 0.18-0.49 kg/m 3 ·s for dermis and subcutis) and the subcutaneous tissue absorption coefficient (0.17-0.21 cm -1 ). By using the developed HTLL model and the determined parameters, temperature depth distributions and the resulting thermal injury to adipocytes were simulated under different treatment conditions. Optimal ranges of the HTTL treatment parameters were determined for different skin types, damaging adipocytes while preserving skin cells. The target subcutaneous temperatures were in the range of 43-47°C, which has been found to lead to programmed adipocyte death. The optimal treatment parameters were further used to define a range of recommended protocols for safe and effective multiarea cycled HTLL treatment of large body surfaces. Specifically, for the set of chosen optimal treatment parameters (4-5 treatment cycles, 1.2 W/cm 2 radiant exposure, and 60-130 W/cm 2 forced air heat-transfer coefficient) the threshold surface temperature during irradiation was found to be in the range of 31-38°C, depending on the skin type and heat-transfer coefficient. The developed numerical model allows for the calculation of the temperature distribution and the resulting injury to adipocyte cells within deeper lying fatty tissuesunder different clinical treatment conditions. It is demonstrated that by measuring the temporal evolution of the skin surface temperatureand by stopping the laser irradiation at predefined skin surface threshold temperatures, it may be possible to monitor and control the effects of the HTLL procedure deeper within the tissue. As such, the model provides a better insight into the HTLL, and may become a tool for defining the range of safe and effective HTLL treatment protocols for patients with different skin types. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Cerebral Perfusion Changes After Osteopathic Manipulative Treatment: A Randomized Manual Placebo-Controlled Trial.

Osteopathic Manipulative Treatment (OMT) is a therapeutic approach aimed at enhancing the body’s self-regulation focusing on somatic dysfunctions correction. Despite evidence of OMT effectiveness, the underlying neurophysiological mechanisms, as well as blood perfusion effects, are still poorly understood. The study aim was to address OMT effects on cerebral blood flow (CBF) in asymptomatic young volunteers as measured by Magnetic Resonance Arterial Spin Labeling (ASL) method. Thirty blinded participants were randomized to OMT or placebo, and evaluated with an MRI protocol before manual intervention (T0), immediately after (T1), and 3 days later (T2). After T0 MRI, participants received 45 min of OMT, focused on correcting whole body somatic dysfunctions, or placebo manual treatment, consisting of passive touches in a protocolled order. After treatment, participants completed a de-blinding questionnaire about treatment perception. Results show significant differences due to treatment only for the OMT group (OMTg): perfusion decreased (compared to T0) in a cluster comprising the left posterior cingulate cortex (PCC) and the superior parietal lobule, while increased at T2 in the contralateral PCC. Furthermore, more than 60% of participants believed they had undergone OMT. The CBF modifications at T2 suggest that OMT produced immediate but reversible effects on CBF.

Numerical simulation of temperature variations in a canine knee joint during therapeutic heating

Tissue heating is used for the treatment of health disorders. However, the benefits of this therapy depend heavily on the temperature reached in the tissues. Values outside the ideal range recommended for therapeutic effects may result in ineffective or tissue-damaging treatments. Thus, understanding the heat transfer process and knowing the temperature distribution in biological tissues are essential factors for this treatment to be applied safely and effectively. In this context, the numerical simulation becomes an interesting tool to understand the temperature field in the different tissues that make up the joint and, thus, to contribute to a better application of the thermal resources used in the clinical practice of physiotherapy. This study aimed to simulate the transient heat transfer in a canine knee joint during the application of a therapeutic heating feature and to investigate the effects of blood perfusion performed at a constant rate (A1 simulation) and as a function of tissue temperature distribution (A2 simulation). The heat diffusion equation was used to model the heat transfer phenomenon. The simulations were performed using the ANSYS-CFX® program. The results obtained from the simulations were compared with in vivo experimental data. The A1 simulation showed a maximum percentage difference of 25.6% compared to the experimental data. In contrast, the highest percentage difference found for the A2 simulation was 9.8%. In conclusion, the results suggest that simulation can be an important tool to evaluate the temperature behaviour of biological tissues during the application of thermal therapeutic resources.

Observation of the effect of blood perfusion combined with penehyclidine hydrochloride injection in the treatment of acute severe organophosphorus pesticide poisoning

Objective To explore the clinical effect of blood perfusion combined with penehyclidine hydrochloride injection in the treatment of acute severe organophosphorus pesticide poisoning. Methods 58 patients with severe organophosphorus pesticide poisoning were selected as the research subjects.By using digital table method, they were randomly divided into observation group and control group, 29 cases in each group.The two groups were given conventional treatment and blood perfusion treatment after admission, the observation group was treated with penehyclidine hydrochloride injection on this base.Before and after treatment, the myocardial enzymes, liver, kidney function index, blood gas analysis, cholinesterase activity, as well as other treatment of the two groups were observed, and the results were compared. Results Compared with the control group, after treatment, the myocardial enzyme, transaminase, serum amylase and creatinine levels in the observation group were significantly lower, cholinesterase level was significantly increased, the oxygen partial pressure increased, the partial pressure of carbon dioxide decreased obviously, the differences were statistically significant(all P<0.05). The hospitalization time and cholinesterase activity recovery time of the observation group were significantly shorter than those of the control group[(12.57±2.14)d vs.(16.35±2.73)d, (5.46±2.29)d vs.(7.61±3.47)d], and the cure rate of the observation group was significantly higher than that of the control group(100.00% vs.82.76%), the differences were statistically significant(t=2.139, 2.208, χ2=5.472, all P<0.05). Conclusion Blood perfusion can directly adsorb organophosphorus pesticide, shorten the recovery time of cholinesterase and reduce the case fatality rate, and it combined with penehyclidine hydrochloride injection not only can improve the clinical curative effect of blood perfusion, but also can protect the organ. Key words: Poisoning; Pesticides; Organophosphorus compounds; Perfusion; Penehyclidine hydrochloride

Numerical analysis of thermal impact of intramyocardial capillary blood flow during radiofrequency cardiac ablation

Purpose: The thermal effect of the intramyocardial blood perfusion on the size of lesions created by radiofrequency cardiac ablation (RFCA) has not been adequately studied to date. Our objective was to assess the impact of including this phenomenon in RFCA computer modelling in terms of the thermal lesion depth created.Methods: A computer model was built and computer simulations were conducted to assess the effect of including the blood perfusion term in the bioheat equation. This term mimics the intramyocardial blood flow (i.e., blood perfusion) in the cardiac wall at the site at which the RFCA is being conducted and hence represents a heat removing mechanism. When considered, blood perfusion rates ranged from 609 to 1719 ml/min/kg. Two electrode design and modes were considered: a non-irrigated electrode with constant temperature mode and an irrigated electrode with constant power mode.Results: All the depths computed without including the blood perfusion term were larger than those that did include it, regardless of perfusion rate. The differences in lesion depth between ignoring and including blood perfusion increased over time; for a 60 s RFCA they were 0.45 and 1 mm for minimum and maximum perfusion rate, respectively. The differences were more or less independent of blood flow in the cardiac chamber, electrode type and ablation mode.Conclusions: The findings suggest that the heat-sink effect of blood perfusion should be taken into account in the case of ablations (>1 minute) such as those conducted in RFCA of the ventricular wall.

Modeling of the temperature field of a tumor tissue loaded by magnetic nanoparticles

Background: Magnetic hyperthermia is a recent therapy used to treat cancer. It is based on the heating of magnetic nanoparticles under the effect of an alternating magnetic field. A mathematical study was considered the effect of heating magnetic nanoparticles to obtain an increase in the desired temperature while causing minimal damage to surrounding healthy tissue. We investigated the thermal response of different materials. An analytical resolution is proposed to solve the bio-heat transfer problem in a two-zone tissue in spherical geometry with blood perfusion and metabolism. Bio-heat equation is used to predict the temperature rise in terms of characteristics of the different magnetic nanoparticles (MNPs), applied magnetic field, and size of the tissue. Methods: The tumor is selectively loaded with magnetic nanoparticles of which are inside the healthy tissue, which does not contain nanoparticles. Under application of the magnetic field, the tumor will experience a rapid increase in temperature, which causes necrosis of the latter while healthy tissue remains safe. Results: Results of the thermal response of three ferro-fluid materials (fcc Fe Pt), magnetite and maghemite (volume fraction of MNPs p = 0.0001), on the tumor (size r =1[cm]) under application of alternating magnetic field (the strength and frequency of applied AC magnetic field H=10 [kA/m] and f=300 [kHz]) show an increase in temperature at the center, which vary from one material to another. It reaches 51°C for (fcc FePt); for magnetite and maghemite, it reaches 43°C. The simulations show that these nanoparticles provide the necessary power to conduct treatment with hyperthermia. The different parameters show that they have an influence on the temperature we observed, ranging from 45°C up to 51°C for volume fraction of MNPs E† = 0.00006, 0.00008, 0.0001. The strength of applied AC magnetic field varies as H= 5, 10, 15(kA/m) and shows significant variation for the temperature ranging between 42°C and 60°C. For the frequency of applied AC magnetic field varied as f=150,300, 450(kHz), the temperature varies between 44°C and 54°C. Finally, the effects of tumor size are considered, the temperature with parameters of (fcc FePt) MNPs, p=0.0001, H=10 (kA/m), and f=300 (kHz) at the center and at the interface of the tumor for a size of 10 mm radius is 51°C and 48°C, respectively. For a tumor of 5 mm radius, we note that the temperature decreases at 49°C and 47°C, which is due to the effect of blood perfusion. Conclusion: Theoretical evaluation of nanoparticles as warming agents for magnetic hyperthermia is carried out by combining the heat generating model and bio-heat transfer equation. Accordingly, (fcc FePt) MNPs were found to have a heat capacity greater than that of other MNPs such as magnetite. This study shows that each item contributes to a significant change in temperature, which causes us to determine the best to achieve optimal treatment. This therapy proves to be promoted with its ability to eliminate tumor tissue while preserving healthy tissue.