The role of malignant tissue on the thermal distribution of cancerous breast

The present work focuses on the integration of analytical and numerical strategies to investigate the thermal distribution of cancerous breasts. Coupled stationary bioheat transfer equations are considered for the glandular and heterogeneous tumor regions, which are characterized by different thermophysical properties. The cross-section of the cancerous breast is identified by a homogeneous glandular tissue that surrounds the heterogeneous tumor tissue, which is assumed to be a two-phase periodic composite with non-overlapping circular inclusions and a square lattice distribution, wherein the constituents exhibit isotropic thermal conductivity behavior. Asymptotic periodic homogenization method is used to find the effective properties in the heterogeneous region. The tissue effective thermal conductivities are computed analytically and then used in the homogenized model, which is solved numerically. Results are compared with appropriate experimental data reported in the literature. In particular, the tissue scale temperature profile agrees with experimental observations. Moreover, as a novelty result we find that the tumor volume fraction in the heterogeneous zone influences the breast surface temperature

Thermal ablation of biological tissues in disease treatment: A review of computational models and future directions

Percutaneous thermal ablation has proved to be an effective modality for treating both benign and malignant tumors in various tissues. Among these modalities, radiofrequency ablation (RFA) is the most promising and widely adopted approach that has been extensively studied in the past decades. Microwave ablation (MWA) is a newly emerging modality that is gaining rapid momentum due to its capability of inducing rapid heating and attaining larger ablation volumes, and its lesser susceptibility to the heat sink effects as compared to RFA. Although the goal of both these therapies is to attain cell death in the target tissue by virtue of heating above 50 oC, their underlying mechanism of action and principles greatly differs. Computational modelling is a powerful tool for studying the effect of electromagnetic interactions within the biological tissues and predicting the treatment outcomes during thermal ablative therapies. Such a priori estimation can assist the clinical practitioners during treatment planning with the goal of attaining successful tumor destruction and preservation of the surrounding healthy tissue and critical structures. This review provides current state-of- the-art developments and associated challenges in the computational modelling of thermal ablative techniques, viz., RFA and MWA, as well as touch upon several promising avenues in the modelling of laser ablation, nanoparticles assisted magnetic hyperthermia and non- invasive RFA. The application of RFA in pain relief has been extensively reviewed from modelling point of view. Additionally, future directions have also been provided to improve these models for their successful translation and integration into the hospital work flow

Optical Diagnostics in Human Diseases

Optical technologies provide unique opportunities for the diagnosis of various pathological disorders. The range of biophotonics applications in clinical practice is considerably wide given that the optical properties of biological tissues are subject to significant changes during disease progression. Due to the small size of studied objects (from μm to mm) and despite some minimum restrictions (low-intensity light is used), these technologies have great diagnostic potential both as an additional tool and in cases of separate use, for example, to assess conditions affecting microcirculatory bed and tissue viability. This Special Issue presents topical articles by researchers engaged in the development of new methods and devices for optical non-invasive diagnostics in various fields of medicine. Several studies in this Special Issue demonstrate new information relevant to surgical procedures, especially in oncology and gynecology. Two articles are dedicated to the topical problem of breast cancer early detection, including during surgery. One of the articles is devoted to urology, namely to the problem of chronic or recurrent episodic urethral pain. Several works describe the studies in otolaryngology and dentistry. One of the studies is devoted to diagnosing liver diseases. A number of articles contribute to the studying of the alterations caused by diabetes mellitus and cardiovascular diseases. The results of all the presented articles reflect novel innovative research and emerging ideas in optical non-invasive diagnostics aimed at their wider translation into clinical practice

A Patient-Specific Approach for Breast Cancer Detection and Tumor Localization Using Infrared Imaging

Breast cancer (BC) is the most common cancer among women in the United States; approximately one out of every 24 women die of related causes. BC screening is a critical factor for improving patient prognosis and survival rate. Infrared (IR) thermography is an accurate, inexpensive and operator independent modality that is not affected by tissue density as it captures surface temperature variations induced by the presence of tumors. A novel patient-specific approach for IR imaging and simulation is proposed. In this work, multi-view IR images of isolated breasts are obtained in the prone position (face down), which allows access to the entire breast surface because the breasts hang freely. The challenge of accurately determining size and location of tumors within the breasts is addressed through numerical simulations of a patient-specific digital breast model. The digital breast models for individual patients are created from clinical images of the breast, such as IR imaging, digital photographs or magnetic resonance images. The numerical simulations of the digital breast model are conducted using ANSYS Fluent, where computed temperature images are generated in the same corresponding views as clinical IRI images. The computed and clinical IRI images are aligned and compared to measure their match. The determination of tumor size and location was conducted through the Levenberg-Marquardt algorithm, which iteratively minimized the mean squared error. The methodology was tested on the breasts of seven patients with biopsy-proven breast cancer with tumor diameters ranging from 8 mm to 27 mm. The method successfully predicted the equivalent tumor diameter within 2 mm and the location was predicted within 6.3 mm in all cases. The time required for the estimation is 48 minutes using a 10-core, 3.41 GHz workstation. The method presented is accurate, fast and has potential to be used as an adjunct modality to mammography in BC screening, especially for dense breasts

Effects of Compression on the Temperature Distribution of a Tissue-Mimicking Material During High-Intensity Focused Ultrasound (HIFU) Ablation

Local blood flow near a high-intensity focused ultrasound (HIFU) target has been shown to decrease ablation effectiveness and predictability, creating a barrier to clinical use for breast cancer treatment. This study investigated the effects of compression on HIFU ablation of a perfused tissue-mimicking material. Gellan gum-based phantoms, with thermal and acoustic properties similar to those of soft tissue, were ablated with a 1.13 MHz HIFU transducer while being subjected to varying levels of external compression. Phantoms were designed with an embedded 6 mm diameter vessel meant to mimic a thermally significant blood vessel near a breast tumor. The internal temperature profile was measured using T-type thin-wire thermocouples embedded in the phantom along the transverse axis. The temperature distributions on opposing lateral sides of the HIFU focal point were measured to determine the effects of compression on heating symmetry. After heating with 30 W for 30 s, the maximum discrepancy between a pair of thermocouples located 2 mm left and right of centerline, respectively, was 40 °C. This maximum discrepancy was observed at a fluid flow rate of 38 mL/min. With applied compression reducing flow to between 28 mL/min and 25 mL/min, the discrepancy between left and right thermocouples was reduced to as low as 5.7 °C. Numerical predictions revealed an agreement with experimental results in the reduction of heating asymmetry as the flow rate decreased from 40 mL/min to 20 mL/min

A Patient-Specific Infrared Imaging Technique for Adjunctive Breast Cancer Screening: A Clinical and Simulation - Based Approach

Breast cancer is currently the most prevalent form of cancer in women with over 266,000 new diagnoses every year. The various methods used for breast cancer screening range in accuracy and cost, however there is no easily reproducible, reliable, low-cost screening method currently available for detecting cancer in breasts, especially with dense tissue. Steady-state Infrared Imaging (IRI) is unaffected by tissue density and has the potential to detect tumors in the breast by measuring and capturing the thermal profile on the breast surface induced by increased blood perfusion and metabolic activity in a rapidly growing malignant tumor. The current work presents a better understanding of IRI as an accurate breast cancer detection modality. A detailed study utilizing IRI-MRI approach with clinical design and validation of an elaborate IRI-Mammo study are presented by considering patient population, clinical study design, image interpretation, and recommended future path. Clinical IRI images are obtained in this study and an ANSYS-based modeling process developed earlier at RIT is used to localize and detect tumor in seven patients without subjective human interpretation. Further, the unique thermal characteristics of tumors that make their signatures distinct from benign conditions are identified. This work is part of an ongoing multidisciplinary collaboration between a team of thermal engineers and numerical modelers at the Rochester Institute of Technology and a team of clinicians at the Rochester General Hospital. The following components were developed to ensure valid experimentation while considering ethical considerations: IRB documentation, patient protocols, an image acquisition system (camera setup and screening table), and the necessary tools needed for image analysis without human interpretation. IRI images in the prone position were obtained and were used in accurately detecting the presence of a cancerous tumor in seven subjects. The size and location of tumor was also confirmed within 7 mm as compared to biopsy-proven pathology information. The study indicates that the IRI-Mammo approach has potential to be a highly effective adjunctive screening tool that can improve the breast cancer detection rates especially for subjects with dense breast tissue. This method is low cost, no-touch, radiation-free and highly portable, making it an attractive candidate as a breast cancer detection modality. Further, the developed method provided insight into infrared features corresponding to other biological images, pathology reports and patient history

A FEEDBACK-BASED DYNAMIC INSTRUMENT FOR MEASURING THE MECHANICAL PROPERTIES OF SOFT TISSUES

In this paper, a novel feedback-based dynamic instrument integrated into a Minimally- Invasive-Surgery (MIS) tool to evaluate the mechanical impedance of soft tissues is presented. This instrument is capable of measuring viscoelasticity of tissues if specific boundary conditions are known. Some important advantages of the proposed instrument are that it is robust and simple in comparison to other similar instruments as it does not require magnitude information of plant’s displacement output and no force sensor is used. The precision and accuracy of the measurements of the proposed instrument for soft tissues is noticeably higher than similar instruments, which are not optimized to work with soft tissues. The proposed dynamic instrument is designed to detect the frequency shifts caused by contacting a soft tissue using an improved phase-locked loop feedback system (closed loop). These frequency shifts can then be used to evaluate the mechanical properties of the tissue. The closed-loop method works fast (with an approximate resonance-frequency-shift rate of 15 Hz per second), and is capable of measuring dy­ namic mechanical properties of viscoelastic tissues, while previous focus was mostly on static/quasi-static elastic modulus. The instrument is used to evaluate the equivalent stiffness of several springs and cantilever beams, mass of reference samples, and also the frequency shifts of several phantoms with injected tumors, noting that these frequency shifts can be used to measure the viscoelasticity of the tissues. It is also shown that the instrument can be used for tumor localization in these phantoms

APPLICATIONS OF HEAT AND MASS TRANSFER ANALYSIS IN BIO-MEDICINE AND MATERIALS

Heat and mass transfer analysis has its application in various fields including automobile, steam-electric power generation, energy systems, HVAC, electronic device cooling and in characterizing and diagnosing diseases. Here we have focused on applying the principles of heat and mass transfer to biological tissue and materials. In the first part we introduce a computational method to simultaneously estimate size, location and blood perfusion of model cancerous breast lesions from surface temperature data. A 2-dimensional computational phantom of axisymmetric tumorous breast with six tissue layers, epidermis, papillary dermis, reticular dermis, fat, gland, muscle layer and spherical tumor was used to generate surface temperature distributions and estimate tumor characteristics iteratively using an inverse algorithm based on the Levenberg-Marquardt method. However, similar steady state temperature profiles for different tumors are insufficient to simultaneously estimate blood perfusion, size and location of tumor. This becomes possible when transient temperature data are used along with steady state data. Thus, in addition to the steady state temperature data, we modified and expanded the inverse algorithm to include transient data that can be captured by dynamic infrared imaging. Blood perfusion is an indicator of the growth rate of the tumor and therefore its evaluation can lead to assessment of tumor malignancy. In the second part we treat X-ray computed tomography (CT) perfusion. The goal was to reduce the total radiation exposure by reducing the number of scans without compromising information integrity. CT scan images obtained from a rabbit model of liver and tumors were processed using the maximum slope (MS) method to estimate blood perfusion in the liver. Limitations of MS method are also discussed. The MS method makes use of key time points, forming the basis of the rationale to explore optimization strategies that utilize variable time intervals, rather than the more common approach of fixed time intervals. Results show that this leads to significant improvement, without compromising diagnostic information. In the last section we explore the magnetic shielding efficacy of superconducting materials and methods to mitigate the effect of necessary discontinuities in superconducting shield

Viscoelasticity Imaging of Biological Tissues and Single Cells Using Shear Wave Propagation

Changes in biomechanical properties of biological soft tissues are often associated with physiological dysfunctions. Since biological soft tissues are hydrated, viscoelasticity is likely suitable to represent its solid-like behavior using elasticity and fluid-like behavior using viscosity. Shear wave elastography is a non-invasive imaging technology invented for clinical applications that has shown promise to characterize various tissue viscoelasticity. It is based on measuring and analyzing velocities and attenuations of propagated shear waves. In this review, principles and technical developments of shear wave elastography for viscoelasticity characterization from organ to cellular levels are presented, and different imaging modalities used to track shear wave propagation are described. At a macroscopic scale, techniques for inducing shear waves using an external mechanical vibration, an acoustic radiation pressure or a Lorentz force are reviewed along with imaging approaches proposed to track shear wave propagation, namely ultrasound, magnetic resonance, optical, and photoacoustic means. Then, approaches for theoretical modeling and tracking of shear waves are detailed. Following it, some examples of applications to characterize the viscoelasticity of various organs are given. At a microscopic scale, a novel cellular shear wave elastography method using an external vibration and optical microscopy is illustrated. Finally, current limitations and future directions in shear wave elastography are presented

Multifunctional Hybrid Materials Based on Polymers: Design and Performance

Multifunctional hybrid materials based on polymers have already displayed excellent commitment in addressing and presenting solutions to existing demands in priority areas such as the environment, human health, and energy. These hybrid materials can lead to unique superior multifunction materials with a broad range of envisaged applications. However, their design, performance, and practical applications are still challenging. Thus, it is highly advantageous to provide a breakthrough in state-of-the-art manufacturing and scale-up technology to design and synthesize advanced multifunctional hybrid materials based on polymers with improved performance.The main objective of this interdisciplinary book is to bring together, at an international level, high-quality elegant collection of reviews and original research articles dealing with polymeric hybrid materials within different areas such as the following:- Biomaterials chemistry, physics, engineering, and processing;- Polymer chemistry, physics and engineering;- Organic chemistry;- Composites science;- Colloidal chemistry and physics;- Porous nanomaterials science;- Energy storage; and- Automotive and aerospace manufacturing