Thermal analysis of cancerous breast model

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.

Key Biophysical and Physiological Properties Impacting the Oxygenation Status of Breast Cancers During Thermo-radiotherapy

Mild hyperthermia at 39-43 °C for 30-60 min is applied locoregionally to improve the oxygenation status of recurrent breast cancers, thus enhancing the efficacy of radio-, chemo-, and immunotherapy. In this context, estimated (or even conflicting) data are often used in computational modelling of tumour oxygenation and simulation of O2 transport. In this chapter, we present information that may help to improve adjuvant thermotherapy delivered immediately prior to radiotherapy of recurrent breast cancers. Data are preferentially derived from clinical investigations; in some cases, measurements in experimental breast cancers are included.The biophysical properties presented for healthy, mostly postmenopausal, human breast (composite glandular-adipose-fibrous tissue) measured under normothermic (NT) conditions and in therapeutically heated breast cancers include tissue water content and tissue density. In general, averaged values of parameters reported for NT conditions are higher in breast cancers than in normal breast tissue, i.e., all ratios breast cancer/normal breast are >1. Mean values observed in breast cancers during mild hyperthermia (mHT) are consistently higher than those in NT tumours. Parameters determining convective transports in healthy breast tissue and breast cancer include blood flow rates, blood volume, exchanging water space, arterio-venous shunt flow, interstitial fluid flow rate, interstitial fluid pressure, microvascular permeability, interstitial hydraulic conductivity, and interstitial flow velocity. In general, averaged values of parameters measured under NT conditions are higher in breast cancers than in healthy breast. Except for interstitial fluid pressure, these values increase upon mHT treatment of cancers. Prime factors determining and describing the oxygenation status of the healthy breast, and in NT- versus mHT-treated breast cancers, include: oxygen (O2) delivery rates, O2- extractions, O2- consumption rates, subepidermal microvascular HbO2, tissue oxygen solubility, oxygen diffusion coefficients, mean O2 partial pressures pO2, hypoxic fractions HF <5 mmHg, oxygen enhancement ratio, and mitochondrial ROS production. With the exception of the mean pO2, O2 extraction rate and tissue O2 saturation all parameters listed are distinctly higher in breast cancers under NT conditions compared to normal breast. Mild hyperthermia results in therapeutically relevant improvements of the oxygenation status of cancers and enhances mitochondrial ROS production, thus improving radiosensitivity. Note: The oxygenation status of the healthy (postmenopausal) breast is very similar to that of the normal human subcutis.

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.

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.

Noninvasive intratumoral thermal dose determination during in vivo magnetic nanoparticle hyperthermia: combining surface temperature measurements and computer simulations

PURPOSE

Noninvasive thermometry during magnetic nanoparticle hyperthermia (MNH) remains a challenge. Our pilot study proposes a methodology to determine the noninvasive intratumoral thermal dose during MNH in the subcutaneous tumor model.

METHODS

Two groups of Ehrlich bearing-mice with solid and subcutaneous carcinoma, a control group (n = 6), and a MNH treated group (n = 4) were investigated. Histopathology was used to evaluate the percentage of non-viable lesions in the tumor. MNH was performed at 301 kHz and 17.5 kA.m^-1, using a multifunctional nanocarrier. Surface temperature measurements were obtained using an infrared camera, where an ROI with 750 pixels was used for comparison with computer simulations. Realistic simulations of the bioheat equation were obtained by combining histopathology intratumoral lesion information and surface temperature agreement of at least 50% of the pixel's temperature data calculated and measured at the surface.

RESULTS

One animal of the MNH group showed tumor recurrence, while two others showed complete tumor remission (monitored for 585 days). Sensitivity analysis of the simulation parameters indicated low tumor blood perfusion. Numerical simulations indicated, for the animals with complete remission, an irreversible tissue injury of 91 ± 5% and 100%, while the one with recurrence had a lower value, 56 ± 7%. The computer simulations also revealed the in vivo heat efficiency of the nanocarrier.

CONCLUSION

A new methodology for determining noninvasively the three-dimensional intratumoral thermal dose during MNH was developed. The method demonstrates the potential for predicting the long-term preclinical outcome of animals treated with MNH.

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.

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.

Thermal analysis of multiple-antenna-excited breast model for breast cancer detection

Infrared thermography (IRT), or thermal imaging has long been proposed as a novel method in early detection of breast cancer. Most of the work done was through the detection of abnormal hotspot, or asymmetries in a thermal texture map. However, the surface temperature may not appear symmetric even for a healthy breast because of variations in blood supply and individual differences. In this paper, a method that is independent of the aforementioned symmetry is proposed. The breast under detection is initially excited by a group of patch antennas. Because of the differences in electromagnetic and thermal properties, the temperature increase will be different for healthy and abnormal tissues. Through the analysis of the temperature changing behavior, comparison of the temperature under each antenna with its vicinity point is done to determine whether cancerous tissue is present or not and further to detect its approximate location. A three-dimensional (3-D) finite-element method (FEM) has been used to simulate the thermal behavior of breast tissue exposed to antenna excitations.