An individualized and multi-segmental bioheat model for predicting local conditions of the human body under various thermal environments.

Thermoregulatory bioheat models have attracted the attention of researchers due to their conformity with the basis of human thermal perception. For this reason, various models have been presented, such as simplified thermoregulatory bioheat (STB), individualized thermoregulatory bioheat (ITB), and multi-segmental thermoregulatory bioheat (MSTB). In the present study and based upon previous models, an individual multi-segment thermoregulatory bioheat (IMTB) model has been introduced. In this model, the body is subdivided into 17 segments and 3 layers, with the blood circulatory system consisting of arteries, veins, and superficial veins. Also, IMTB can evaluate the individual parameters effects (such as height, weight, gender, and age) on physiological parameters and active/passive systems. Finally, this new model was evaluated in human thermal response predictions over a wide range of transient and steady-state environmental conditions (5.0< Tair(°C) <50.0, 31.0 < RH (%)<70.0) and various individual characteristics (male and female, 20 < age (years) < 69, 50

Would personal cooling vest be effective for use during exercise by people with thoracic spinal cord injury?

People with thoracic spinal cord injury (SCI), named people with paraplegia (PA), are vulnerable to thermal heat stress during exercise due to disruption in their thermal physiology. Using personal cooling vests with phase change material (PCM) or ice presents a possible solution for PA to suppress the increase in core temperature and body heat storage. With the limited published experimental studies about effective cooling vest for PA, this work aims to develop an altered PA bioheat model combined with cooling vest model to study cooling vest performance during exercise. The integrated PA bioheat and vest models predict core and skin temperatures, latent and sensible heat losses and change in body heat storage for PA with and without a cooling vest. The models were validated with published experimental data on PA without the cooling vest and on PA with two cooling vests; one using PCM at melting temperature of 15 °C and the other using ice packets during exercise. It was observed that sensible heat losses at the four torso segments (abdomen, lower back, chest and upper back) increased with the vest case compared to the no-vest case; while, latent heat losses decreased compared to the no-vest case. However, insignificant change was seen in core temperatures and body heat storage as was also reported experimentally. The performance of each of the cooling vest during exercise on PA was dependent on skin coverage area and melting temperatures.

A heterogeneous tissue model for treatment planning for magnetic resonance-guided laser interstitial thermal therapy.

We evaluated a physics-based model for planning for magnetic resonance-guided laser interstitial thermal therapy for focal brain lesions. Linear superposition of analytical point source solutions to the steady-state Pennes bioheat transfer equation simulates laser-induced heating in brain tissue. The line integral of the photon attenuation from the laser source enables computation of the laser interaction with heterogeneous tissue. Magnetic resonance thermometry data sets (n = 31) were used to calibrate and retrospectively validate the model's thermal ablation prediction accuracy, which was quantified by the Dice similarity coefficient (DSC) between model-predicted and measured ablation regions (T > 57 °C). A Gaussian mixture model was used to identify independent tissue labels on pre-treatment anatomical magnetic resonance images. The tissue-dependent optical attenuation coefficients within these labels were calibrated using an interior point method that maximises DSC agreement with thermometry. The distribution of calibrated tissue properties formed a population model for our patient cohort. Model prediction accuracy was cross-validated using the population mean of the calibrated tissue properties. A homogeneous tissue model was used as a reference control. The median DSC values in cross-validation were 0.829 for the homogeneous model and 0.840 for the heterogeneous model. In cross-validation, the heterogeneous model produced a DSC higher than that produced by the homogeneous model in 23 of the 31 brain lesion ablations. Results of a paired, two-tailed Wilcoxon signed-rank test indicated that the performance improvement of the heterogeneous model over that of the homogeneous model was statistically significant (p < 0.01).

A new local thermal bioheat model for predicting the temperature of skin thermoreceptors of individual body tissues.

Under non-uniform environments, the human body thermal perception depends on the thermal responses of cutaneous thermoreceptors (TRs) in different body parts. However, skin TRs thermal response includes static and dynamic parts depending on TRs temperature and its change rate, respectively. Thus, it is necessary to evaluate the time-dependent temperatures of cutaneous TRs in different body parts. The Pennes equation is one of the most important bioheat equations for computing the temperature of biological bodies, but, it has been used for evaluating the mean temperature of the whole body, considering average properties for all body parts. In the present study, the Pennes equation was solved for 16 body parts by considering appropriate thermal/physiological properties for each segment. In addition, a controlling system was added to the Pennes equation by applying the thermoregulatory mechanisms of 65-node Tanabe (65MN) model. The time-dependent skin temperatures of the 16 body segments were obtained by solving the localized thermoregulatory bioheat equation. The validation of the present model was carried out using published experimental data and a good agreement was found.

Thermoregulation in premature infants: A mathematical model.

PURPOSE: In 2010, approximately 14.9 million babies (11.1%) were born preterm. Because preterm infants suffer from an immature thermoregulatory system they have difficulty maintaining their core body temperature at a constant level. Therefore, it is essential to maintain their temperature at, ideally, around 37°C. For this, mathematical models can provide detailed insight into heat transfer processes and body-environment interactions for clinical applications. METHODS: A new multi-node mathematical model of the thermoregulatory system of newborn infants is presented. It comprises seven compartments, one spherical and six cylindrical, which represent the head, thorax, abdomen, arms and legs, respectively. The model is customizable, i.e. it meets individual characteristics of the neonate (e.g. gestational age, postnatal age, weight and length) which play an important role in heat transfer mechanisms. The model was validated during thermal neutrality and in a transient thermal environment. RESULTS: During thermal neutrality the model accurately predicted skin and core temperatures. The difference in mean core temperature between measurements and simulations averaged 0.25±0.21°C and that of skin temperature averaged 0.36±0.36°C. During transient thermal conditions, our approach simulated the thermoregulatory dynamics/responses. Here, for all infants, the mean absolute error between core temperatures averaged 0.12±0.11°C and that of skin temperatures hovered around 0.30°C. CONCLUSIONS: The mathematical model appears able to predict core and skin temperatures during thermal neutrality and in case of a transient thermal conditions.

A Multi-Segmented Human Bioheat Model for Asymmetric High Temperature Environments.

In workplaces such as steel, power grids, and construction, firefighters and other workers often encounter non-uniform high-temperature environments, which significantly increase the risk of local heat stress and local heat discomfort for the workers. In this paper, a multi-segment human bioheat model is developed to predict the human thermal response in asymmetric high-temperature environments by considering the sensitivity of the modeling to angular changes in skin temperature and the effects of high temperatures on human thermoregulatory and physiological responses simultaneously. The extended model for asymmetric high-temperature environments is validated with the current model results and experimental data. The result shows that the extended model predicts the human skin temperature more accurately. Under non-uniform high-temperature conditions, the local skin temperature predictions are highly consistent with the experimental data, with a maximum difference of 2 °C. In summary, the proposed model can accurately predict the temperature of the human core and skin layers. It has the potential to estimate human physiological and thermoregulatory responses under uniform and non-uniform high-temperature environments, providing technical support for local heat stress and local thermal discomfort protection.

Mathematical modelling of thermoregulation processes for premature infants in closed convectively heated incubators.

The low-weight newborns and especially the premature infants have difficulty in maintaining their temperature in the range considered to be normal. Several studies revealed the importance of thermal environment and moisture to increase the survival rate of newborns. This work models the process of heat exchange and energy balance in premature newborns during the first hours of life in a closed incubator. In addition, a control problem was proposed and solved in order to maintain thermal stability of premature newborns to increase their rate of survival and weight. For this purpose, we propose an algorithm to control the temperature inside the incubator. It takes into account the measurements of the body temperature of a premature newborn which are recorded continuously. We show that using this model the temperature of a premature newborn inside the incubator can be kept in a thermal stability range.

Numerical simulation and heat transfer in sand therapy in Uyghur medicine / 中南大学学报(医学版)

Objective To investigate the mechanism of heat transfer process in sand therapy in Uyghur medicine. Methods A mathematical model was developed to describe the heat transfer process between human body and the sand during sand therapy. Temperature field was numerically simulated and analyzed based on this model. Results Temperature field in both human tissues and sand was calculated. The surface temperature of the sand and skin surface changed significantly at the beginning of the sand therapy, while sand temperature (5 cm deep) almost kept constant. The skin temperature dramatically increased at the beginning of the sand therapy and then slightly dropped. When sand was deeper than 10 cm, the thickness of sand would not influence the temperature field in human tissues during sand therapy. High initial temperature of sand might cause harmful skin burn. Threshold skin burn occurred if initial temperature of sand was higher than 64.6 ℃ and if the therapy lasted more than 30 minutes.Conclusion Temperature fieled in human tissues varies significantly with the initial temperature of sand, thickness of sand, and duration of therapy.