An improved three-dimensional direct numerical modelling and thermal analysis of a female breast with tumour

Induced Current Electro-Thermal Imaging for Breast Tumor Detection: A Numerical and Experimental Study

This study proposes using magnetically induced currents in medical infrared imaging to increase the temperature contrast due to the electrical conductivity differences between tumors and healthy tissues. There are two objectives: (1) to investigate the feasibility of this active method for surface and deep tumors using numerical simulations, and (2) to demonstrate the use of this method through different experiments conducted with phantoms that mimic breast tissues. Tumorous breasts were numerically modeled and simulated in active and passive modes. At 750 kHz, the applied current was limited for breast tissue-tumor conductivities (0.3 S/m and 0.75 S/m) according to the local specific absorption rate limit of 10 W/kg. Gelatin-based and mashed potato phantoms were produced to mimic tumorous breast tissues. In the simulation studies, the induced current changed the temperature contrast on the imaging surface, and the tumor detection sensitivity increased by 4 mm. An 11-turn 70-mm-long solenoid coil was constructed, 20 A current was applied for deep tumors, and a difference of up to 0.4 ∘ C was observed in the tumor location compared with the temperature in the absence of the tumor. Similarly, a 23-turn multi-layer coil was constructed, and a temperature difference of 0.4 ∘ C was observed. The temperature contrast on the body surface changed, and the tumor detection depth increased with the induced currents in breast IR imaging. The proposed active thermal imaging method was validated using numerical simulations and in vitro experiments.

A computing platform to analyze breast abnormalities using infrared images

The present work shows a computational tool developed in the MATLAB platform. Its main functionality is to evaluate a thermal model of the breast. This computational infrastructure consists of modules in which manipulate the infrared images and calculate breast temperature profiles. It also allows the analysis of breast nodules. The different modules of the framework are interconnected through an interface which the major purpose is to automatize the whole process of the infrared image analysis, in a quick and organized way. The tool is initially supplied with a three-dimensional mesh that represents the substitute geometry of the patient's breast together with her infrared images which are transformed into temperature matrices. Through these matrices, the frontal and lateral mappings are performed by specified modules. This process generates an image and a text file with all the temperatures associated to the nodes of the surface mesh. The developed tool is also able to manage the use of a commercial mesh generation program and a computational fluid dynamics code, the FLUENT, in order to validate the technique by the use of a parametric analysis. In these analyses, the tumor may have several geometric shapes and different locations within the breast.

Plasmonic photothermal therapy in the near-IR region using gold nanostars

Photothermal therapy using nanoparticles is a prominent technique for cancer treatment. The principle is to maximize the heat conversion efficiency using plasmonic nanoparticle-light interaction. Due to their unique optical characteristics derived from their anisotropic structure, gold nanostars (GNSs) have gotten significant attention in photothermal therapy. To design a proper cancer treatment, it is vital to study the thermal effect induced close to the gold nanoparticles, in the vicinity, and the cancerous tissue. A temperature-dependent 2D model based on finite element method models is commonly used to simulate near-IR tumor ablation. The bioheat equation describes the photothermal effect within the GNSs and the environment. Surface cooling and heating strategies, such as the periodical heating method and a reduced laser irradiation area, were investigated to address surface overheating problems. We also determined that the optimal laser radius depends on tumor aspect ratio and laser intensity. Our results provide guidelines to evaluate a safe and feasible temperature range, treatment time, optimal laser intensity, and laser radius to annihilate a tumor volume.

Numerical Analysis of Temperature Distribution Profiles of Breast Tissues with Cyst and Tumor of Different sizes and Locations

Breast cancer causes more deaths among all types of cancers. Efforts have been put to study the change in temperature distribution profile of the breast in presence of an abnormality. By applying Pennes's bio-heat equation, a 2D finite element model is developed for the heat transfer mechanism. Surface temperature gradients due to the presence of abnormalities at various depths and sizes are analyzed. The results show that the presence of a cyst decreases the temperature whereas the occurrence of tumor increases the temperature inside the breast. It is observed that abnormal tissue having a radius less than 1.5cm and depth greater than 5cm, has a negligible effect on the surface temperature profile. The highest change in surface temperature is observed when a cyst or tumor is larger and present near the skin. The simulation results help in the better interpretation of the thermal images and calibration of infrared camera. This study could be helpful in the early diagnosis of breast cancer.

Review of Thermal and Physiological Properties of Human Breast Tissue

Electromagnetic thermal therapies for cancer treatment, such as microwave hyperthermia, aim to heat up a targeted tumour site to temperatures within 40 and 44 °C. Computational simulations used to investigate such heating systems employ the Pennes’ bioheat equation to model the heat exchange within the tissue, which accounts for several tissue properties: density, specific heat capacity, thermal conductivity, metabolic heat generation rate, and blood perfusion rate. We present a review of these thermal and physiological properties relevant for hyperthermia treatments of breast including fibroglandular breast, fatty breast, and breast tumours. The data included in this review were obtained from both experimental measurement studies and estimated properties of human breast tissues. The latter were used in computational studies of breast thermal treatments. The measurement methods, where available, are discussed together with the estimations and approximations considered for values where measurements were unavailable. The review concludes that measurement data for the thermal and physiological properties of breast and tumour tissue are limited. Fibroglandular and fatty breast tissue properties are often approximated from those of generic muscle or fat tissue. Tumour tissue properties are mostly obtained from approximating equations or assumed to be the same as those of glandular tissue. We also present a set of reliable data, which can be used for more accurate modelling and simulation studies to better treat breast cancer using thermal therapies.

Breast Thermography as an Adjunct Tool to Monitor the Chemotherapy Response in a Triple Negative BIRADS V Cancer Patient: A Case Study

Prior studies have reported that breast thermography is a potential adjunct tool to mammography in early cancer detection, especially in developing countries with limited medical facilities. This non-invasive, safe, and painless screening tool can reduce the mortality due to cancer by early detection and monitoring. This prospective study aims to analyze changes in static breast thermograms of a BIRADS V category breast cancer patient to assess the response to Neoadjuvant chemotherapy (NACT) in locally advanced cancer and to compare with thermograms of a BIRADS II category benign patient. Breast thermograms of the malignant and benign patients in five different views were taken using FLIR E40 thermal camera under strict acquisition protocols. Details of the patient along with the thermograms were recorded pre and post NACT. There is a qualitative reduction in the warm region of the surface after the first cycle of chemotherapy treatment. Thermal, fractal, and statistical analysis of thermograms is performed for both patients. In the patient with aggressive ductal carcinoma, the difference in the mean surface temperature between contralateral breasts is high, which is reduced after the first cycle of NACT. This preliminary study indicates that breast thermography can potentially be used as an effective non-invasive, non-contact, and radiation-free tool to analyze the effect of NACT on patients with different stages of breast cancer. This study also signifies the role of the thermography technique in reaching a largely rural population with limited medical resources for early cancer screening.

Computational Simulation of Breast Tissue with Lesion Characterized by a Thermal Gradient Oriented to Anomalies Smaller than 1 cm of Diameter

In this work, the computational simulation of thermal gradients related to internal lesions according to the phenomenon of pathological angiogenesis is proposed, this is based on the finite element method, and using a three¬dimensional geometric model adjusted to suit the real female anatomy. The simulation of the thermal distribution was based on the bioheating equation; it was carried out using the COMSOL Multiphysics® software. As a result, the simulation of both internal and superficial thermal distributions associated to lesions smaller than 1 cm and located inside the simulated breast tissue were obtained. An increase in temperature on the surface of the breast of 0.1 ° C was observed for a lesion of 5 mm in diameter and 15 mm in deep. A qualitative validation of the model was carried out by contrasting the simulation of anomalies of 10 mm in diameter at different depths (10, 15 and 20 mm) proposed in the literature, with the simulation of the model proposed here, obtaining the same behavior for the three cases.Clinical Relevance- The 3D computational tool adjusted to suit the anatomy of the real female breast allows obtaining the temperature distribution inside and on the surface of the tissue in healthy cases and with abnormalities associated with temperature elevations. It is an important characteristic of the model when the behavior of the parameters inside the tissue needs to be analyzed.

Theoretical Analysis for Using Pulsed Heating Power in Magnetic Hyperthermia Therapy of Breast Cancer

In magnetic hyperthermia, magnetic nanoparticles (MNPs) are used to generate heat in an alternating magnetic field to destroy cancerous cells. This field can be continuous or pulsed. Although a large amount of research has been devoted to studying the efficiency and side effects of continuous fields, little attention has been paid to the use of pulsed fields. In this simulation study, Fourier's law and COMSOL software have been utilized to identify the heating power necessary for treating breast cancer under blood flow and metabolism to obtain the optimized condition among the pulsed powers for thermal ablation. The results showed that for small source diameters (not larger than 4 mm), pulsed powers with high duties were more effective than continuous power. Although by increasing the source domain the fraction of damage caused by continuous power reached the damage caused by the pulsed powers, it affected the healthy tissues more (at least two times greater) than the pulsed powers. Pulsed powers with high duty (0.8 and 0.9) showed the optimized condition and the results have been explained based on the Arrhenius equation. Utilizing the pulsed powers for breast cancer treatment can potentially be an efficient approach for treating breast tumors due to requiring lower heating power and minimizing side effects to the healthy tissues.

A Computational Method for the Estimation of the Geometrical and Thermophysical Properties of Tumor Using Contact Thermometry

Contact thermometry is the measurement of surface temperature using sensors in contact with the medium. These surface temperatures can be potential indicators of any abnormality possibly a tumor. This research work aims to present a computation method that makes use of contact thermometry to estimate the geometric center, size, and thermophysical properties of breast tumor. Wearable thermal sensors captured real-time surface temperature readings from discrete point locations. The continuous heat distribution over the domain was formulated using forward heat transfer analysis. The optimization method estimated tumor parameters of the breast, and a three-dimensional thermal model was developed from the estimated parameters. Laboratory experiments on breast phantoms were done to validate the estimation method. Furthermore, real-time temperature readings of human subjects were recorded, and the estimated location and size were then compared with the mammogram results. It was found that the estimated two-dimensional geometric center and the size in diameter of the tumor closely match with the mammogram results. Further, the thermophysical properties estimated using the proposed method had a higher order in subjects having a tumor making it a tool for breast cancer screening.

An improved analytical model for heat flow in cancerous tumours to avoid thermal injuries during hyperthermia

The present study highlights an analytical hybrid scheme consisted of a shift of variables and finite integral transform for analysing a local thermal non-equilibrium (LTNE) bioheat model. This model can have utilised to be a betterment of prediction of the temperature field in the localised hyperthermia therapy (LHT) for the treatment of cancer patients. As the hyperthermia treatment is only the application in living tissues, an appropriate initial condition for the therapeutic thermal response is proposed instead of a constant temperature taken in the previous studies based on the 1-D heat flow. The present analysis suggests the therapeutic exposure time of 7776.8s (2.16 h) with constant heat flux and the exposure time of 10969.9s (3.06 h) with a sinusoidal heat flux within the usual temperature range of the hyperthermia (in a combination of thermal ablation and medium temperature hyperthermia) to be more effective in the treatment protocol. The presented results show that fatal injuries (tissue trauma, thermal burn, etc.) of internal organs might be possible to avoid by the current therapeutic condition. Therefore, this study may nullify the adverse effect of the existing model with the constant heating and consequently, the repercussion of the several therapeutic variables is to estimate with the development of a thermal profile for the suitability of a therapeutic condition. On the other hand, the present study well matches with the published analysis in case of both the theoretical and experimental (live tissues of the pig due to unavailability of real-time data on the human body) studies and it found the maximum deviation of the thermal response as 2.26% and 2.66%, respectively.

Pre-operative Assessment of Ablation Margins for Variable Blood Perfusion Metrics in a Magnetic Resonance Imaging Based Complex Breast Tumour Anatomy: Simulation Paradigms in Thermal Therapies

BACKGROUND AND OBJECTIVES

Image-guided medical interventions facilitates precise visualization at treatment site. The conformal prediction for sparing healthy tissue fringes precisely in the vicinity of irregular tumour anatomy remains clinically challenging. Pre-clinical image-based computational modelling is imperative as it helps in enhancement of treatment quality, augmenting clinical-decision making, while planning, targeting, controlling, monitoring and assessing treatment response with an effective risk assessment before the onset of treatment in clinical settings. In this study, the influence of heat deposition rate (SAR), exposure duration, and variable blood perfusion metrics for a patient-specific breast tumour is quantified considering the tumour margins thereby suggesting need of geometrically accurate models.

METHODS

A three-dimensional realistic model mimicking dimensions of a female breast, comprising ~1.7 cm irregular tumour, was generated from patient specific two-dimensional DICOM format MRI images through image segmentation tools MIMICS 19.0® and 3-Matic 11.0® which is finally exported to COMSOL Multiphysics 5.2® as a volumetric mesh for finite element analysis. The Pennes bioheat transfer model and Arrhenius thermal damage model of cell-death are integrated to simulate a coupled biophysics problem. A comparative blood perfusion analysis is done to evaluate the response of tumour during heating considering thermal damage extent, including the tumour margins while sparing critical adjoining healthy tissues.

RESULTS

The evaluated thermal damage zones for 1 mm, 2 mm and 3 mm fringe heating region (beyond tumour boundary) reveals 0.09%, 0.21% and 0.34% thermal damage to the healthy tissue (which is <1%) and thus successful necrosis of the tumour. The iterative computational experiments suggests treatment margins < 5 mm are sufficient enough as heating beyond 3 mm fringe layer leads to higher damage surrounding the tumour approximately 1.5 times the tumour volume. Further, the heat-dosage requirements are 22% more for highly perfused tumour as compared to moderately perfused tumour with an approximate double time to ablate the whole tumour volume.

CONCLUSIONS

Depending on the blood perfusion characteristics of a tumour, it is a trade-off between heat-dosage (SAR) and exposure/treatment duration to get desired thermal damage including the irregular tumour boundaries while taking into account, the margin of healthy tissue. The suggested patient-specific integrated multiphysics-model based on MRI-Images may be implemented for pre-treatment planning based on the tumour blood perfusion to evaluate the thermal ablation zone dimensions clinically and thereby avoiding the damage of off-target tissues. Thus, risks involving underestimation or overestimation of thermal coagulation zones may be minimised while preserving the surrounding normal breast parenchyma.

Breast tumor parameter estimation and interactive 3D thermal tomography using discrete thermal sensor data

This work uses a simple low-cost wearable device embedded with discrete thermal sensors to map the breast skin surface temperature. A methodology has been developed to estimate diameter, blood perfusion, metabolic heat generation and location in X, Y, Z coordinate of tumor from this discrete set of data. An interactive 3D thermal tomography was developed which provides a detailed 3D thermal view of the breast anatomy. Using this system, the user can interactively rotate and slice the 3D thermal image of the breast for a detailed study of the tumor. Finite element method (FEM) and an evolution-based inverse method were used for the parameter estimation. The method was first validated using phantom experiments and the results obtained were within an error of 10% (0.005 W cm^-3) for heat generation and 15% (0.3 cm) for heater location. Further validation was carried out through clinical trials on 60 human subjects. Estimated blood perfusion rate and metabolic heat generation rate exhibit distinguishable difference between cancerous and non-cancerous breast. Estimated diameter and location of tumor in cancerous breast shows good agreement with the actual clinical reports. We have obtained a sensitivity of 82.78% and specificity of 87.09%. Proposed breast tumor parameter estimation methodology with interactive 3D thermal tomography is a good screening tool for breast cancer detection and also useful for clinicians to find out location including depth.

In silico study of enhanced permeation and retention effect and hyperthermia of porous tumor

Nanotechnology has recently gained fame for its extensive use in biomedical applications particularly in magnetic fluid hyperthermia (MFH) of tumors. The magnetic nanoparticles (MNPs) are usually injected into the tumor either intravenously or through direct needle injection. Depending on the location of the tumor, the needle approach may not be appropriate and in the case, when the nanoflow rate is higher, it may produce cracks in the tumor. In this scenario, the intravenous approach following the enhanced permeation and retention effect (EPR) effect proves advantageous. In this paper, we have simulated the EPR effect of nanofluid flowing from blood vessels to the tumor through epithelial cells spacing and then its diffusion in the tumor interstitium using COMSOL Multiphysics. The velocity in the blood vessel and diffusion in the tumor have been simulated and analyzed using Finite Element Method (FEM) based models of Navier-Stokes equations and convection-diffusion equation. The simulation results show that the velocity and concentration are higher in the blood vessel and it decreases slowly while moving through epithelial spacing to the tumor interstitium. The heat transfer in the tumor interstitium is simulated and analyzed for temperature distribution quantitatively.

An introduction to the Cyrcadia Breast Monitor: A wearable breast health monitoring device

BACKGROUND

The most common breast cancer detection modalities are generally limited by radiation exposure, discomfort, high costs, inter-observer variabilities in image interpretation, and low sensitivity in detecting cancer in dense breast tissue. Therefore, there is a clear need for an affordable and effective adjunct modality that can address these limitations. The Cyrcadia Breast Monitor (CBM) is a non-invasive, non-compressive, and non-radiogenic wearable device developed as an adjunct to current modalities to assist in the detection of breast tissue abnormalities in any type of breast tissue.

METHODS

The CBM records thermodynamic metabolic data from the breast skin surface over a period of time using two wearable biometric patches consisting of eight sensors each and a data recording device. The acquired multi-dimensional temperature time series data are analyzed to determine the presence of breast tissue abnormalities. The objective of this paper is to present the scientific background of CBM and also to describe the history around the design and development of the technology.

RESULTS

The results of using the CBM device in the initial clinical studies are also presented. Twenty four-hour long breast skin temperature circadian rhythm data was collected from 93 benign and 108 malignant female study subjects in the initial clinical studies. The predictive model developed using these datasets could differentiate benign and malignant lesions with 78% accuracy, 83.6% sensitivity and 71.5% specificity. A pilot study of 173 female study subjects is underway, in order to validate this predictive model in an independent test population.

CONCLUSIONS

The results from the initial studies indicate that the CBM may be valuable for breast health monitoring under physician supervision for confirmation of any abnormal changes, potentially prior to other methods, such as, biopsies. Studies are being conducted and planned to validate the technology and also to evaluate its ability as an adjunct breast health monitoring device for identifying abnormalities in difficult-to-diagnose dense breast tissue.

Thermal Imaging - An Emerging Modality for Breast Cancer Detection: A Comprehensive Review

Breast cancer is not preventable. To reduce the death rate and improve the survival chances of breast cancer patients, early and accurate detection is the only panacea. Delay in diagnosis of this disease causes 60% of deaths. Thermal imaging is a low-risk modality for early breast cancer decision making without injecting any form of energy into the human body. Thermography as a screening tool was first introduced and well accepted in 1956. However, a study in 1977 found that it lagged behind other screening tools and is subjective. Soon after, its use was discontinued. This review discusses various screening tools used to detect breast cancer with a focus on thermography along with their advantages and shortcomings. With the maturation of thermography equipment and technological advances, this technique is emerging and has become the refocus of many biomedical researchers across the globe in the past decade. This study dispenses an exhaustive review of the work done related to interpretation of breast thermal variations and confers the discipline, frameworks, and methodologies used by different authors to diagnose breast cancer. Different performance metrics like accuracy, specificity, and sensitivity have also been examined. This paper outlines the most pressing research gaps for future work to improvise the accuracy of results for diagnosis of breast abnormalities using image processing tools, mathematical modelling and artificial intelligence. However, supplementary research is needed to affirm the potential of this technology for predicting breast cancer risk effectively. Altogether, our findings inform that it is a promising research problem and a potential solution for early detection of breast cancer in younger women.

Determining the thermal characteristics of breast cancer based on high-resolution infrared imaging, 3D breast scans, and magnetic resonance imaging

For over the three decades, various researchers have aimed to construct a thermal (or bioheat) model of breast cancer, but these models have mostly lacked clinical data. The present study developed a computational thermal model of breast cancer based on high-resolution infrared (IR) images, real three-dimensional (3D) breast surface geometries, and internal tumor definition of a female subject histologically diagnosed with breast cancer. A state-of-the-art IR camera recorded IR images of the subject’s breasts, a 3D scanner recorded surface geometries, and standard diagnostic imaging procedures provided tumor sizes and spatial locations within the breast. The study estimated the thermal characteristics of the subject’s triple negative breast cancer by calibrating the model to the subject’s clinical data. Constrained by empirical blood perfusion rates, metabolic heat generation rates reached as high as 2.0E04 W/m³ for normal breast tissue and ranged between 1.0E05–1.2E06 W/m³ for cancerous breast tissue. Results were specific to the subject’s unique breast cancer molecular subtype, stage, and lesion size and may be applicable to similar aggressive cases. Prior modeling efforts are briefly surveyed, clinical data collected are presented, and finally thermal modeling results are presented and discussed.

Mathematical Modeling of Breast Tumor Destruction Using Fast Heating during Radiofrequency Ablation

In oncology, hyperthermia is understood as a planned, controlled technique of heating cancerous changes in order to destroy their cells or stop their growth. In clinical practice, hyperthermia is used in combination with radiotherapy, chemotherapy, or immunological therapy. During the hyperthermia, the tissue is typically exposed to a temperature in the range of 40–45 °C, the exception is thermoablation, during which the temperatures reach much higher values. Thermoablation is characterized by the use of high temperatures up to 90 °C. The electrode using the radiofrequency is inserted into the central area of the tumor. Interstitial thermoablation is used to treat, among others, breast and brain cancer. The therapy consists of inducing coagulation necrosis in an area that is heated to very high temperatures. Mathematical modeling is based on the use of a coupled thermo-electric model, in which the electric field is described by means of the Laplace equation, while the temperature field is based on the Pennes equation. Coupling occurs at the level of the additional source function in the Pennes equation. The temperature field obtained in this way makes it possible to calculate the Arrhenius integral as a determinant of the destruction of biological tissue. As a result of numerical calculations regarding the temperature field and the Arrhenius integral, it can be concluded that, with the help of numerical tools and mathematical modeling, one can simulate the process of destroying cancerous tissue.

The influence of size, depth and histologic characteristics of invasive ductal breast carcinoma on thermographic properties of the breast

Invasive breast carcinoma is the most common oncologic disease worldwide. The existing diagnostic methods use morphologic changes in the breast to diagnose a carcinoma when it has reached a certain size. Therefore, it is important to augment the morphologic diagnostic examinations with a new method that focuses on characteristics other than morphology such as electromagnetic changes produced by cancer. 50 adult female patients with confirmed ductal carcinoma following a core biopsy due to a suspicious breast mass were included in the study. They underwent breast thermography using a specially designed infrared camera. The data collected was statistically analyzed to determine how the presence of a tumor and its histologic characteristics influence breast thermographic properties. Twenty eight [56 %] patients in the study had an abnormal thermogram. Following statistical analysis, it was found that temperature of the diseased breast was directly correlated to tumor volume [p=0.009] and negatively correlated to depth of tumor [p=0.042]. Tumors that were ER+ and PR+ tumors produced warmer temperatures [p=0.017 and p=0.038 respectively] than tumors without these receptors. HER2 status and Ki-67 index had no statistical correlation with breast temperature. Tumor size, distance from the skin surface and receptor status cause changes in breast thermographic properties. Despite technical advances in the field of thermography, there are still contradictory results associated with thermography. Its diagnostic abilities are generally poorer than conventional methods and its use in breast cancer screening or as an adjunctive tool for diagnostic purposes is not recommended.

Applicability of active infrared thermography for screening of human breast: a numerical study

Active infrared thermography is a fast, painless, noncontact, and noninvasive imaging method, complementary to mammography, ultrasound, and magnetic resonance imaging methods for early diagnosis of breast cancer. This technique plays an important role in early detection of breast cancer to women of all ages, including pregnant or nursing women, with different sizes of breast, irrespective of either fatty or dense breast. This proposed complementary technique makes use of infrared emission emanating from the breast. Emanating radiations from the surface of the breast under test are detected with an infrared camera to map the thermal gradients over it, in order to reveal hidden tumors inside it. One of the reliable active infrared thermographic technique, linear frequency modulated thermal wave imaging is adopted to detect tumors present inside the breast. Further, phase and amplitude images are constructed using frequency and time-domain data analysis schemes. Obtained results show the potential of the proposed technique for early diagnosis of breast cancer in fatty as well as dense breasts.

Quantification of Thermal Injury to the Healthy Tissue Due to Imperfect Electrode Placements During Radiofrequency Ablation of Breast Tumor

Radiofrequency ablation (RFA) has emerged as an alternative treatment modality for treating various tumors with minimum intervention. The application of RFA in treating breast tumor is still in its infancy stage. Nevertheless, promising results have been obtained while treating early stage localized breast cancer with RFA procedure. The outcome of RFA is tremendously dependent on the precise insertion of the electrode into the geometric center of the tumor. However, there remains plausible chances of inaccuracies in the electrode placement that can result in slight displacement of the electrode tip from the actual desired location during temperature-controlled RFA application. The present numerical study aims at capturing the influence of inaccuracies in electrode placement on the input energy, treatment time and damage to the surrounding healthy tissue during RFA of breast tumor. A thermo-electric analysis has been performed on three-dimensional heterogeneous model of multilayer breast with an embedded early stage spherical tumor of 1.5 cm. The temperature distribution during the RFA has been obtained by solving the coupled electric field equation and Pennes bioheat transfer equation, while the ablation volume has been computed using the Arrhenius cell death model. It has been found that significant variation in the energy consumption, time required for complete tumor necrosis, and the shape of ablation volume among different positions of the electrode considered in this study are prevalent.

THREE-DIMENSIONAL MODEL OF METASTATIC TUMOR ANGIOGENESIS IN RESPONSE TO ANTI-ANGIOGENIC FACTOR ANGIOSTATIN

Surgeons observed that primary tumors are capable of suppressing the growth of their metastases by generating anti-angiogenic factor angiostatin. A three-dimensional (3D) mathematical model of development of the metastatic tumor vasculature is presented to simulate the morphology and construction of 3D microvascular networks under the inhibitory effect of anti-angiogenic factor angiostatin excreted by the primary tumor. The simulation results demonstrate that metastatic tumor microvascular density (MVD) decreases by about 60%, 58% and 52%, respectively, at [Formula: see text], 7 and 14 days under the effect of anti-angiogenic factor angiostatin. The abnormal geometric and morphological features of 3D microvasculature networks inside and outside the metastatic tumor improve in the presence of angiostatin. The present model may allow to simulate experimental tests and may provide theoretical models for clinical research of anti-angiogenic therapy strategies.

THERMAL IMAGING AS AN ADJUNCT TOOL FOR IDENTIFYING FETAL GROWTH – A PILOT STUDY

Monitoring the fetal growth and diagnosing any possible abnormality plays a vital role in ensuring the healthy growth of a fetus. Certain health issues like Hyperthermia, Premature Rupture of Membranes (PROM) and Intrauterine Growth Restriction (IUGR) has to be diagnosed early. A pilot study comprising of 27 pregnant and 2 non-pregnant subjects was conducted to check the effectiveness of Thermal imaging in predicting the fetal growth. The heat dissipated by the fetus to the maternal abdominal wall is acquired as a surface thermal distribution. These images were processed qualitatively and quantitatively for better understanding. There was a consistent higher thermal pattern for pregnant women. A more pronounced temperature pattern is notable in the umbilical region that correlates with gestation age. However, as thermal pattern varies with age, gestation period and BMI, it is advisable to track the same person and compare the images for better assessment. This pilot study justifies the need for more elaborate study in building a database for classification and interpretation of thermogram to detect fetal abnormality with reduced human interpretation.

TWO-DIMENSIONAL FINITE ELEMENT MODEL TO STUDY THERMO BIOMECHANICS IN PERIPHERAL REGIONS OF HUMAN LIMBS DUE TO EXERCISE IN COLD CLIMATE

Human beings are equipped with thermo sensitivity, thermoregulation and thermo protection for maintaining the structure and function of their body organs. The thermoregulatory responses and disturbances caused by physical activity in thermo biomechanics of human body organs are not well understood. The mechanism of thermoregulation exhibits a beautiful coordination of biophysical process in order to balance distribution caused by a biothermal system due to physical exercise and other abnormal conditions. In view of above, a model has been developed to study the thermal dynamics in peripheral region of human limbs immediately after exercise under cold climatic conditions. The human limb is assumed to be of cylindrical shape. The peripheral region of limb is divided into three natural components namely epidermis, dermis and subdermal tissues. Appropriate boundary conditions have been framed based on the physical condition of the problem. Finite difference has been employed for time variable and the finite element method is employed along radial and angular direction. The numerical results have been used to obtain temperature profiles in the peripheral region immediately after continuous exercise for a two-dimensional unsteady state case. These results have been used to analyze the thermal disturbances caused by the different intensities of physical exercise in the peripheral region of human limbs. Such a model can be developed to study the generated thermal information which can be useful to biomedical science to analyze the impact of thermal stress on mechanism of thermoregulation causing thermal injuries like heat cramps, heat exhaustion and heat stroke. The results give the idea about the capacity of biothermo mechanisms of human limbs in counting balance. The thermal stress is caused by different intensities of physical exercise. These results can be useful for the biomedical scientists to understand the thermal discomfort caused by different intensities of physical exercise and the time period of rest required to overcome discomfort. Further, the result can be useful to biomedical scientists for developing protocols for physical exercise and rest required by the subject for different intensities of physical exercise and prevent thermal injuries in the workers and sportsmen.

Preliminary results of a new approach for three-dimensional reconstruction of Dynamic AngioThermography (DATG) images based on the inversion of heat equation

Dynamic AngioThermography (DATG) is a contact-plate technique capable of producing a digital representation of breast vascularity. The inception and growth of a tumor are associated with neoangenesis, which may result in a demonstrable alteration in the regional blood flow, while in normal health conditions the vascularity remains unchanged throughout life. DATG, if included in the clinical evaluation for breast cancer, could potentially improve the accuracy of the diagnosis of this disease. Conventional DATG is limited, however, in that it is a projection (i.e. two-dimensional) imaging technique that does not provide any information on the depth and its effect on the pattern of the perfusion revealed by this technique. In fact, the blood pattern is detected by projecting temperature signals on the plate, thus acquiring a digital two-dimensional image. In this article we propose a new approach for extracting information on depth through the inversion of the Fourier heat equation. The idea is to extract the information along the third axis while acquiring and analyzing the temporal sequence during the process of image formation. The method implemented has been tested on a dedicated "electric phantom" and in one in vivo experiment. In spite of the limits of these preliminary tests, the experimental results have shown that this method makes it possible to obtain a 3D representation of the vascularity. Although it appears to be promising, further validation and characterization of our technique are required.

Segmenting breast cancerous regions in thermal images using fuzzy active contours

Breast cancer is the main cause of death among young women in developing countries. The human body temperature carries critical medical information related to the overall body status. Abnormal rise in total and regional body temperature is a natural symptom in diagnosing many diseases. Thermal imaging (Thermography) utilizes infrared beams which are fast, non-invasive, and non-contact and the output created images by this technique are flexible and useful to monitor the temperature of the human body. In some clinical studies and biopsy tests, it is necessary for the clinician to know the extent of the cancerous area. In such cases, the thermal image is very useful. In the same line, to detect the cancerous tissue core, thermal imaging is beneficial. This paper presents a fully automated approach to detect the thermal edge and core of the cancerous area in thermography images. In order to evaluate the proposed method, 60 patients with an average age of 44/9 were chosen. These cases were suspected of breast tissue disease. These patients referred to Tehran Imam Khomeini Imaging Center. Clinical examinations such as ultrasound, biopsy, questionnaire, and eventually thermography were done precisely on these individuals. Finally, the proposed model is applied for segmenting the proved abnormal area in thermal images. The proposed model is based on a fuzzy active contour designed by fuzzy logic. The presented method can segment cancerous tissue areas from its borders in thermal images of the breast area. In order to evaluate the proposed algorithm, Hausdorff and mean distance between manual and automatic method were used. Estimation of distance was conducted to accurately separate the thermal core and edge. Hausdorff distance between the proposed and the manual method for thermal core and edge was 0.4719 ± 0.4389, 0.3171 ± 0.1056 mm respectively, and the average distance between the proposed and the manual method for core and thermal edge was 0.0845 ± 0.0619, 0.0710 ± 0.0381 mm respectively. Furthermore, the sensitivity in recognizing the thermal pattern in breast tissue masses is 85 % and its accuracy is 91.98 %.A thermal imaging system has been proposed that is able to recognize abnormal breast tissue masses. This system utilizes fuzzy active contours to extract the abnormal regions automatically.

Parameter estimation of breast tumour using dynamic neural network from thermal pattern

This article presents a new approach for estimating the depth, size, and metabolic heat generation rate of a tumour. For this purpose, the surface temperature distribution of a breast thermal image and the dynamic neural network was used. The research consisted of two steps: forward and inverse. For the forward section, a finite element model was created. The Pennes bio-heat equation was solved to find surface and depth temperature distributions. Data from the analysis, then, were used to train the dynamic neural network model (DNN). Results from the DNN training/testing confirmed those of the finite element model. For the inverse section, the trained neural network was applied to estimate the depth temperature distribution (tumour position) from the surface temperature profile, extracted from the thermal image. Finally, tumour parameters were obtained from the depth temperature distribution. Experimental findings (20 patients) were promising in terms of the model's potential for retrieving tumour parameters.

Thermal analysis of induced damage to the healthy cell during RFA of breast tumor

Effective pre-clinical computational modeling strategies have been demonstrated in this article to enable risk free clinical application of radiofrequency ablation (RFA) of breast tumor. The present study (a) determines various optimal regulating parameters required for RFA of tumor and (b) introduces an essential clinical monitoring scheme to minimize the extent of damage to the healthy cell during RFA of tumor. The therapeutic capabilities offered by RFA of breast tumor, viz., the rise in local temperature and induced thermal damage have been predicted by integrating the bioheat transfer model, the electric field distribution model and the thermal damage model. The mathematical model has been validated with the experimental results available in the literature. The results revealed that, the effective damage of tumor volume sparing healthy tissue essentially depends on the voltage, the exposure time, the local heat distribution, the tumor stage and the electrode geometric configuration. It has been confirmed that, the assessment of damage front can accurately determine the extent of damage as compared to the thermal front. The study further evaluates the damaged healthy and tumor volumes due to RFA of different stages of breast cancer. The assessment of cell survival and damage fractions discloses the propensity of reappearance/healing of tumor cells after treatment.

GROWTH OF MALIGNANT CELLS AND THERMODYNAMICS

In the present paper, certain thermodynamic relations are considered to study tumor growth and how the mechanisms, responsible for the cell killing by temperature change in abnormal cells, can be estimated from direct measurements, during evolution of a tumor. The problem is considered in its most general form and the discussion focuses on how significant results can be estimated from: (i) The stress system acting on the tumor, tumor pressure and tumor volume changes measured by ultra-sonic computerized tomography, (ii) entropy change and entropy production, measured from the heat capacity profiles, and (iii) the chemical potential changes measured by fluorescent labeling techniques; all of them supported by other techniques based on histo-chemical and microscopic methods.

TUMOR CELL GROWTH SUBJECTED TO CORRELATED NOISES AND TIME DELAY

The tumor cell growth with time-delayed feedback driven by correlated noises under the immune surveillance are investigated within an anti-tumor model. The effects of the noise correlation strength and time delay on the stationary probability distribution, the average tumor cell population and the mean first passage time (MFPT) are analyzed in detail based on the delay Fokker–Planck equation. The effects of the correlation strength and time delay could play the same role in the average tumor cell population, but play opposite role in the MFPT. In addition, the role of the correlation strength and time delay for different activation thresholds of immune system is explored.

Potentialities of steady-state and transient thermography in breast tumour depth detection: A numerical study

Breast thermography still has inherent limitations that prevent it from being fully accepted as a breast screening modality in medicine. The main challenges of breast thermography are to reduce false positive results and to increase the sensitivity of a thermogram. Further, it is still difficult to obtain information about tumour parameters such as metabolic heat, tumour depth and diameter from a thermogram. However, infrared technology and image processing have advanced significantly and recent clinical studies have shown increased sensitivity of thermography in cancer diagnosis. The aim of this paper is to study numerically the possibilities of extracting information about the tumour depth from steady state thermography and transient thermography after cold stress with no need to use any specific inversion technique. Both methods are based on the numerical solution of Pennes bioheat equation for a simple three-dimensional breast model. The effectiveness of two approaches used for depth detection from steady state thermography is assessed. The effect of breast density on the steady state thermal contrast has also been studied. The use of a cold stress test and the recording of transient contrasts during rewarming were found to be potentially suitable for tumour depth detection during the rewarming process. Sensitivity to parameters such as cold stress temperature and cooling time is investigated using the numerical model and simulation results reveal two prominent depth-related characteristic times which do not strongly depend on the temperature of the cold stress or on the cooling period.

Finite element modeling of haptic thermography: A novel approach for brain tumor detection during minimally invasive neurosurgery

Intraoperative Thermal Imaging (ITI) is a novel neuroimaging method that can potentially locate tissue abnormalities and hence improves surgeon's diagnostic ability. In the present study, thermography technique coupled with artificial tactile sensing method called "haptic thermography" is utilized to investigate the presence of an abnormal object as a tumor with an elevated temperature relative to the normal tissue in the brain. The brain tissue is characterized as a hyper-viscoelastic material to be descriptive of mechanical behavior of the brain tissue during tactile palpation. Based on a finite element approach, Magnetic Resonance Imaging (MRI) data of a patient diagnosed to have a brain tumor is utilized to simulate and analyze the capability of haptic thermography in detection and localization of brain tumor. Steady-state thermal results prove that temperature distribution is an appropriate outcome of haptic thermography for the superficial tumors while heat flux distribution can be used as an extra thermal result for deeply located tumors.

A 3D COUPLED MATHEMATICAL MODEL FOR THE GROWTH OF AVASCULAR SOLID TUMOR

We develop a coupled mathematical model of avascular tumor growth based on porous media mechanics. This comprises of the migration of tumor cells (TCs), the degradation of extracellular matrix (ECM), the transport of matrix-degrading enzymes (MDEs), the seepage of tissue fluid and the supplement and consumption of oxygen. The simulation that a solid tumor grows in the micro-environment composed of the pre-existing capillaries and the surrounding tissues, and the specific property of varying porosity with the growth of TCs in a tumor micro-environment are taken into account. We propose functional coefficients for fluid seepage and oxygen diffusion, and incorporate the convection–diffusion of oxygen and the convection of MDEs. From this modified model the main findings include: first, a solid tumor originating in the inlet region undergoes necrosis in the outlet region because of a low supply of oxygen, while a solid tumor originating in the outlet region undergoes necrosis at the primary site because of overconsumption of oxygen; second, tumors further from capillaries grow faster than tumors close to adjacent capillaries; third, the pre-existing capillaries cause some impact to the transport of those chemical factors involved in tumor growth, and further affect tumor migration and necrosis.

IN SILICO MODELING OF TUMOR GROWTH

Tumor growth is strongly coupled with both residual stress generated during the growth process and also biochemical factors. Several models have already been proposed to capture tumor growth considering either diffusion of nutrients concentration or residual stresses inside a tumor. In this work, a new method was proposed to model the generated residual stress in a growing solid using the continuum framework. This method was coupled with energy metabolism to predict the behavior of a soft tissue tumor. Moreover, it was shown that the main reason of vascular collapse in the middle of a tumor or vascular reopening in the tumor core can be the residual stress, generated during the growth.

BREAST THERMOGRAPHY AS A POTENTIAL NON-CONTACT METHOD IN THE EARLY DETECTION OF CANCER: A REVIEW

This review paper discusses recent research achievements in medical thermography with concerns about the possibility of early breast cancer detection. With the advancements in infrared (IR) technology, image processing methods, and the pathophysiological-based knowledge of thermograms, IR screening is sufficiently mature to be utilized as a first-line complement to both health managing and clinical prognosis. In addition, it explains the performance and environmental conditions in identifying thermography for breast tumor imaging under strict indoor controlled environmental circumstances. An irregular thermogram is indicated as a significant biological risk marker for the presence or growth of breast tumors. Breast thermography is completely non-contact, with no form of radiation and compression. It is useful for all women of all ages, for pregnant and breastfeeding women, for women with implants, for women with dense or fibrocystic breasts, for women on hormone replacement therapy, and for pre or post menopausal women.

Breast thermography is specifically worthwhile during the early stages of fast tumor growth, which is not yet recognizable by mammography as thermography is a physiological test while mammography is an anatomical one. Often, physiological changes precede anatomical changes. This early detection of irregular tissue liveliness gives breast thermography the potential to be greatly useful and economical as an imaging program and provides the opportunity to apply non-invasive treatment to reform breast tissue activity. The non-radiating nature of thermography also permits repeated images. Thus, changes can be compared over time and the results of protective approaches can be observed to ensure utmost care of breast cells.

Thermal analysis of cancerous breast model

Breast cancer is one of the most common and dangerous cancers. Subsurface breast cancer lesions generate more heat and have increased blood supply when compared to healthy tissue, and this temperature rise is mirrored in the skin surface temperature. The rise in temperature on the skin surface, caused by the cancerous lesion, can be measured noninvasively using infrared thermography, which can be used as a diagnostic tool to detect the presence of a lesion. However, its diagnostic ability is limited when image interpretation relies on qualitative principles. In this study, we present a quantitative thermal analysis of breast cancer using a 3D computational model of the breast. The COMSOL FEM software was used to carry out the analysis. The effect of various parameters (tumor size, location, metabolic heat generation and blood perfusion rate) on the surface temperature distribution (which can be measured with infrared thermography) has been analyzed. Key defining features of the surface temperature profile have been identified, which can be used to estimate the size and location of the tumor based on (measured) surface temperature data. In addition, we employed a dynamic cooling process, to analyze surface temperature distributions during cooling and thermal recovery as a function of time. In this study, the effect of the cooling temperature on the enhancement of the temperature differences between normal tissue and cancerous lesions is evaluated. This study demonstrates that a quantification of temperature distributions by computational modeling, combined with thermographic imaging and dynamic cooling can be an important tool in the early detection of breast cancer.

EARLY DETECTION AND VISUALIZATION OF BREAST TUMOR WITH THERMOGRAM AND NEURAL NETWORK

Although mammography is still the benchmark technique for breast cancer detection, many advantages of thermography make it a suitable adjunct tool for early detection. This paper describes the development of a computer-aided system for use together with thermography to assist in the detection and visualization/analysis of breast tumors. The system consists of a detection module for predicting the presence of tumors from thermograms, and a visualization module for generating the 3-D volumetric geometry of the suspected tumor inside the breast based on the 2-D thermogram. Detection is achieved through an artificial neural network taking the thermogram image as input, while the visualization is obtained by generating the 3-D model of the breast that produces a matching thermal image as the thermogram under a 3-D finite element analysis. A study with 200 subjects indicate that the detection sensitivity was good but the specificity was poor, but the reverse performance result was true for another back-propagation neural network which used physiological data instead of thermograms as input. This suggests that overall prediction capability can be improved by appropriate combination of the two results.

The association of infrared imaging findings of the breast with hormone receptor and human epidermal growth factor receptor 2 status of breast cancer

RATIONALE AND OBJECTIVES

Evidence on breast infrared (IR) imaging and its association with estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) statuses of breast cancers is limited. The aim of this study was to investigate the association of IR imaging findings and ER, PR, and HER2 status in breast cancers.

MATERIALS AND METHODS

A total of 163 women with 171 pathologically proven breast cancers underwent IR imaging of the breast before surgery. Five IR signs were used to score the lesions: IR1, the temperature difference (ΔT) of the lesion site from that of the contralateral mirror image site; IR2, ΔT of the lesion site from that of the adjacent normal breast tissue in the same breast; IR3, abnormal vascular morphologic patterns; IR4, focal bulge or edge sign with back heat at the lesion site; and IR5, asymmetric thermographic pattern between the lesion site and the contralateral breast. The association of different IR signs with ER, PR, and HER2 status was evaluated using Fisher's exact test.

RESULTS

IR1 was inversely associated with ER (P = .010) and PR status (P = .039). IR2 was inversely related to PR status (P = .020). IR5 was inversely associated with ER (P = .037) and PR (P = .022) status. No IR sign was associated with HER2 status. Triple-negative (ER-negative, PR-negative, and HER2-negative) cancers tended to show higher IR1 scores compared to other types of cancers (P = .029).

CONCLUSION

Breast IR findings were associated with ER and PR status of breast cancers. Triple-negative cancers more frequently featured higher IR1 scores than other types of cancers.

Modeling static and dynamic thermography of the human breast under elastic deformation

An abnormal thermogram has been shown to be a reliable indicator of increased risk of breast cancer. Numerical modeling techniques for thermography are proposed to quantify the complex relationships between the breast thermal behaviors and the underlying physiological/pathological conditions. Previous thermal modeling techniques did not account for gravity-induced elastic deformation arising from various body postures, nor did they suggest that a dynamic thermal procedure may be used to enhance clinical diagnosis. In this paper, 3D finite element method (FEM)-based thermal and elastic modeling techniques are developed to characterize comprehensively both the thermal and elastic properties of normal and tumorous breast tissues during static and dynamic thermography. In the steady state, gravity-induced breast deformation is found to cause an upper-lower asymmetric surface temperature contrast for sitting/standing up body posture, even though all the thermal and elastic properties are assumed uniform. Additionally, the tumor-induced surface temperature alterations are found to be caused primarily by shallow tumors and to be less sensitive to tumor size than to tumor depth. In the dynamic state, the breast exhibits distinctive temporal patterns that are associated with distinct thermal events: cold stress and thermal recovery induced by changes in the ambient temperature. Specifically, the tumor-induced thermal contrast shows an opposite initial change and delayed peak as compared with the deformation-induced thermal contrast. These findings are expected to provide a stronger foundation for, and greater specificity and precision in, thermographic diagnosis, and treatment of breast cancer.

The feasibility of irreversible electroporation for the treatment of breast cancer and other heterogeneous systems

Developments in breast cancer therapies show potential for replacing simple and radical mastectomies with less invasive techniques. Localized thermal techniques encounter difficulties, preventing their widespread acceptance as replacements for surgical resection. Irreversible electroporation (IRE) is a non-thermal, minimally invasive focal ablation technique capable of killing tissue using electric pulses to create irrecoverable nano-scale pores in the cell membrane. Its unique mechanism of cell death exhibits benefits over thermal techniques including rapid lesion creation and resolution, preservation of the extracellular matrix and major vasculature, and reduced scarring. This study investigates applying IRE to treat primary breast tumors located within a fatty extracellular matrix despite IREs dependence on the heterogeneous properties of tissue. In vitro experiments were performed on MDA-MB-231 human mammary carcinoma cells to determine a baseline electric field threshold (1000 V/cm) to cause IRE for a given set of pulse parameters. The threshold was incorporated into a three-dimensional numerical model of a heterogeneous system to simulate IRE treatments. Treatment-relevant protocols were found to be capable of treating targeted tissue over a large range of heterogeneous properties without inducing significant thermal damage, making IRE a potential modality for successfully treating breast cancer. Information from this study may be used for the investigation of other heterogeneous tissue applications for IRE.