20 research outputs found
Numerical Modeling of the Internal Temperature in the Mammary Gland
The microwave thermometry method for the diagnosis of breast cancer is based
on an analysis of the internal temperature distribution.This paper is devoted
to the construction of a mathematical model for increasing the accuracy of
measuring the internal temperature of mammary glands, which are regarded as a
complex combination of several components, such as fat tissue, muscle tissue,
milk lobules, skin, blood flows, tumor tissue. Each of these biocomponents is
determined by its own set of physical parameters. Our numerical model is
designed to calculate the spatial distributions of the electric microwave field
and the temperature inside the biological tissue. We compare the numerical
simulations results to the real medical measurements of the internal
temperature.Comment: 8 pages, 4 figure
Numerical 3D modeling of heat transfer in human tissues for microwave radiometry monitoring of Brown fat metabolismo
Background: Brown adipose tissue (BAT) plays an important role in whole body metabolism and could potentially mediate weight gain and insulin sensitivity. Although some imaging techniques allow BAT detection, there are currently no viable methods for continuous acquisition of BAT energy expenditure. We present a non-invasive technique for long term monitoring of BAT metabolism using microwave radiometry. Methods: A multilayer 3D computational model was created in HFSS™ with 1.5 mm skin, 3-10 mm subcutaneous fat, 200 mm muscle and a BAT region (2-6 cm3) located between fat and muscle. Based on this model, a log-spiral antenna was designed and optimized to maximize reception of thermal emissions from the target (BAT). The power absorption patterns calculated in HFSS™ were combined with simulated thermal distributions computed in COMSOL® to predict radiometric signal measured from an ultra-low-noise microwave radiometer. The power received by the antenna was characterized as a function of different levels of BAT metabolism under cold and noradrenergic stimulation. Results: The optimized frequency band was 1.5-2.2 GHz, with averaged antenna efficiency of 19%. The simulated power received by the radiometric antenna increased 2-9 mdBm (noradrenergic stimulus) and 4-15 mdBm (cold stimulus) corresponding to increased 15-fold BAT metabolism. Conclusions: Results demonstrated the ability to detect thermal radiation from small volumes (2-6 cm3) of BAT located up to 12 mm deep and to monitor small changes (0.5°C) in BAT metabolism. As such, the developed miniature radiometric antenna sensor appears suitable for non-invasive long term monitoring of BAT metabolism
Passive microwave radiometry in biomedical studies
Passive microwave radiometry (MWR) measures natural emissions in the range 1–10 GHz from proteins, cells, organs and the whole human body. The intensity of intrinsic emission is determined by biochemical and biophysical processes. The nature of this process is still not very well known. Infrared thermography (IRT) can detect emission several microns deep (skin temperature), whereas MWR allows detection of thermal abnormalities down to several centimeters (internal or deep temperature). MWR is noninvasive and inexpensive. It requires neither fluorescent nor radioactive labels, nor ionizing or other radiation. MWR can be used in early drug discovery as well as preclinical and clinical studies
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
Target-specific multiphysics modeling for thermal medicine applications
Dissertation to obtain the degree of Doctor of Philosophy in Biomedical EngineeringThis thesis addresses thermal medicine applications on murine bladder hyperthermia
and brain temperature monitoring. The two main objectives are interconnected by the
key physics in thermal medicine: heat transfer. The first goal is to develop an analytical
solution to characterize the heat transfer in a multi-layer perfused tissue. This analytical
solution accounts for important thermoregulation mechanisms and is essential to
understand the fundamentals underlying the physical and biological processes
associated with heat transfer in living tissues. The second objective is the development
of target-specific models that are too complex to be solved by analytical methods. Thus,
the software for image segmentation and model simulation is based on numerical
methods and is used to optimize non-invasive microwave antennas for specific targets.
Two examples are explored using antennas in the passive mode (probe) and active mode
(applicator).
The passive antenna consists of a microwave radiometric sensor developed for rapid
non-invasive feedback of critically important brain temperature. Its design parameters
are optimized using a power-based algorithm. To demonstrate performance of the
device, we build a realistic model of the human head with separate temperaturecontrolled
brain and scalp regions. The sensor is able to track brain temperature with 0.4
°C accuracy in a 4.5 hour long experiment where brain temperature is varied in a 37 °C,
27 °C and 37 °C cycle.
In the second study, a microwave applicator with an integrated cooling system is used to
develop a new electro-thermo-fluid (multiphysics) model for murine bladder
hyperthermia studies. The therapy procedure uses a temperature-based optimization
algorithm to maintain the bladder at a desired therapeutic level while sparing remaining
tissues from dangerous temperatures. This model shows that temperature dependent
biological properties and the effects of anesthesia must be accounted to capture the
absolute and transient temperature fields within murine tissues. The good agreement
between simulation and experimental results demonstrates that this multiphysics model
can be used to predict internal temperatures during murine hyperthermia studies
Recommended from our members
A Robust and Artifact Resistant Algorithm of Ultrawideband Imaging System for Breast Cancer Detection.
Goal: Ultrawideband radar imaging is regarded as one of the most promising alternatives for breast cancer detection. A range of algorithms reported in literature show satisfactory tumor detection capabilities. However, most of algorithms suffer significant deterioration or even fail when the early-stage artifact, including incident signals and skin-fat interface reflections, cannot be perfectly removed from received signals. Furthermore, fibro-glandular tissue poses another challenge for tumor detection, due to the small dielectric contrast between glandular and cancerous tissues. Methods: This paper introduces a novel Robust and Artifact Resistant (RAR) algorithm, in which a neighborhood pairwise correlation-based weighting is designed to overcome the adverse effects from both artifact and glandular tissues. In RAR, backscattered signals are time-shifted, summed, and weighted by the maximum combination of the neighboring pairwise correlation coefficients between shifted signals, forming the intensity of each point within an imaging area. Results: The effectiveness was investigated using 3-D anatomically and dielectrically accurate finite-difference-time-domain numerical breast models. The use of neighborhood pairwise correlation provided robustness against artifact, and enabled the detection of multiple scatterers. RAR is compared with four well-known algorithms: delay-and-sum, delay-multiply-and-sum, modified-weighted-delay-and-sum, and filtered-delay-and-sum. Conclusion: It has shown that RAR exhibits improved identification capability, robust artifact resistance, and high detectability over its counterparts in most scenarios considered, while maintaining computational efficiency. Simulated tumors in both homogeneous and heterogonous, from mildly to moderately dense breast phantoms, combining an entropy-based artifact removal algorithm, were successfully identified and localized. Significance: These results show the strong potential of RAR for breast cancer screening
Contribution to the Design AND Implementation of a Microwave Tomography System for Breast Cancer Detection
Abstract This thesis represents a contribution to the design and implementation of a microwave tomography system applied to breast cancer detection. Microwave tomography is an imaging technique that aims to reconstruct the permittivity and conductivity of an unknown object from measurements of its scattered field. This technique has been used in a variety of applications such as non-destructive testing, geophysical surveys and biomedical imaging. Here, we will concentrate in the breast cancer detection, where this technique has received a lot of attention in the recent years. A microwave tomography system usually involves two separate parts, a measurement system capable of performing accurate measurements of the scattered field and a set of algorithms for solving the inverse problem of retrieving the permittivity and conductivity spatial distribution of the unknown object from the scattered field measurements. This inverse problem is particularly difficult to solve, since it is non-linear and ill posed. In order to achieve a good reconstruction of the object, we need to illuminate it under several independent conditions, such as different antenna positions, frequencies or polarizations. In this thesis, we concentrate in the design of an efficient illumination configuration that tries to maximize the quality of the reconstructed images. After a literature review, it is observed that most of the proposed measurement systems share a common configuration, where in order to maximize the comfort of the patient; the antennas are arranged in a cylindrical or hemi-spherical configuration. On the other hand, the most popular method for breast cancer detection is mammography, where an X-ray image of the compressed breast at two different projections is performed. Taking this into account, two alternative configurations based on a compression of the breast are proposed, the camera and waveguide configurations. The main hypothesis behind this proposition is that a compression of the breast will allow placing the receivers very close to the breast where it is possible to measure the evanescent component of the scattered field and thus allow an enhancement of the quality of the reconstructed images. In order to prove this hypothesis, a rigorous study of the proposed configurations against a classical circular tomography setup is performed, and we determine under what conditions the reconstructed images can be enhanced. Next, the placement of the receiving antennas very close to the object under test, poses some challenges for an accurate measurement of the scattered fields, since the measurement probe itself can distort the quantity to be measured. For this purpose, an enhanced version of a previously designed near-field probe based on the modulated scattering technique is designed and validated. The probe is then used in the practical implementation of the proposed waveguide configuration. polarisations à l’intérieur du guide d’onde.----------Résumé Cette thèse représente une contribution à la conception et mise en œuvre d’un système de tomographie micro-onde pour la détection du cancer du sein. La tomographie micro-onde est une technique d’imagerie donc le but est de reconstruire la permittivité et la conductivité d’un objet inconnu à partir des mesures du champ diffusé par l’objet. Cette technique a été utilisée dans une variété d'applications comme le control non-destructif, la géophysique et l’imagerie biomédicale. Dans cette thèse, l'emphase sera mise sur la détection du cancer du sein, où cette technique a reçu énormément d’attention dans les années précédentes. Un système de tomographie micro-onde est normalement composé de deux parties séparées; un système de mesures capable de fournir des mesures précises du champ diffusé et une série d’algorithmes capable de retrouver la distribution spatiale de la permittivité et la conductivité de l’objet inconnu à partir des mesures du champ diffusé. Ce problème inverse est particulièrement difficile à résoudre, puisqu’il est non-linéaire et mal posé. Dans le but d’obtenir une bonne reconstruction de l’objet, il est nécessaire d’illuminer l’objet sous une série de conditions indépendantes, comme différentes positions d’antenne, des fréquences ou des polarisations. Dans cette thèse, l'emphase sera mise sur la conception d’une configuration d’illumination efficace qui essaie de maximiser la qualité des images reconstruites. Après une revue de littérature, on observe que la plupart des systèmes de mesures partagent une configuration commune o\`u les antennes sont placées sur une configuration cylindrique ou hémisphérique pour maximiser le confort de la patiente. D’un autre coté, la méthode la plus populaire pour le dépistage du cancer du sein est la mammographie, o\`u on utilise une image à rayons X du sein compressé en deux projections. En prenant compte de ce fait, on propose deux configurations alternatives basées sur la compression du sein, les configurations caméra et guide d’onde. L’hypothèse derrière cette proposition est que la compression du sein permet de placer les capteurs très près de ce dernier donc il est possible de mesurer la composante évanescente du champ diffusé, ce qui pourrait permettre l'amélioration de la qualité des images reconstruites. Afin de prouver cette hypothèse, une étude rigoureuse des configurations proposées et sa comparaison avec une configuration classique de tomographie circulaire est réalisée. Grace à cette étude on détermine les conditions qui permettent d’améliorer les images reconstruites.
Le placement des capteurs très proche de l’objet sous test représente un défi pour une mesure précise des champs diffusés, puisque le capteur lui-même peut perturber le signal à mesurer. Pour cette raison, une version améliorée d’une sonde de mesure en champ proche basé sur la technique de diffusion modulée est conçue et validée. La sonde est utilisée pour la mise en œuvre de la configuration guide d’onde proposée. Un réseau d’antennes est développé pour l’excitation de différents modes avec différente
Advanced ultrawideband imaging algorithms for breast cancer detection
Ultrawideband (UWB) technology has received considerable attention in recent years as it is regarded to be able to revolutionise a wide range of applications. UWB imaging for breast cancer detection is particularly promising due to its appealing capabilities and advantages over existing techniques, which can serve as an early-stage screening tool, thereby saving millions of lives. Although a lot of progress has been made, several challenges still need to be overcome before it can be applied in practice. These challenges include accurate signal propagation modelling and breast phantom construction, artefact resistant imaging algorithms in realistic breast models, and low-complexity implementations. Under this context, novel solutions are proposed in this thesis to address these key bottlenecks.
The thesis first proposes a versatile electromagnetic computational engine (VECE) for simulating the interaction between UWB signals and breast tissues. VECE provides the first implementation of its kind combining auxiliary differential equations (ADE) and convolutional perfectly matched layer (CPML) for describing Debye dispersive medium, and truncating computational domain, respectively. High accuracy and improved computational and memory storage efficiency are offered by VECE, which are validated via extensive analysis and simulations. VECE integrates the state-of-the-art realistic breast phantoms, enabling the modelling of signal propagation and evaluation of imaging algorithms.
To mitigate the severe interference of artefacts in UWB breast cancer imaging, a robust and artefact resistant (RAR) algorithm based on neighbourhood pairwise correlation is proposed. RAR is fully investigated and evaluated in a variety of scenarios, and compared with four well-known algorithms. It has been shown to achieve improved tumour detection and robust artefact resistance over its counterparts in most cases, while maintaining high computational efficiency. Simulated tumours in both homogeneous and heterogeneous breast phantoms with mild to moderate densities, combined with an entropy-based artefact removal algorithm, are successfully identified and localised.
To further improve the performance of algorithms, diverse and dynamic correlation weighting factors are investigated. Two new algorithms, local coherence exploration (LCE) and dynamic neighbourhood pairwise correlation (DNPC), are presented, which offer improved clutter suppression and image resolution. Moreover, a multiple spatial diversity (MSD) algorithm, which explores and exploits the richness of signals among different transmitter and receiver pairs, is proposed. It is shown to achieve enhanced tumour detection even in severely dense breasts.
Finally, two accelerated image reconstruction mechanisms referred to as redundancy elimination (RE) and annulus predication (AP) are proposed. RE removes a huge number of repetitive operations, whereas AP employs a novel annulus prediction to calculate millions of time delays in a highly efficient batch mode. Their efficacy is demonstrated by extensive analysis and simulations. Compared with the non-accelerated method, RE increases the computation speed by two-fold without any performance loss, whereas AP can be 45 times faster with negligible performance degradation
Global Monitoring for Security and Stability (GMOSS) - Integrated Scientific and Technological Research Supporting Security Aspects of the European Union
This report is a collection of scientific activities and achievements of members of the GMOSS Network of Excellence during the period March 2004 to November 2007. Exceeding the horizon of classical remote-sensing-focused projects, GMOSS is characterized by the integration of political and social aspects of security with the assessment of remote sensing capabilities and end-users support opportunities. The report layout reflects the work breakdown structure of GMOSS and is divided into four parts.
Part I Concepts and Integration addresses the political background of European Security Policy and possibilities for Earth Observation technologies for a contribution. Besides it illustrates integration activities just as the GMOSS Gender Action Plan or a description of the GMOSS testcases.
Part II of this book presents various Application activities conducted by the network partners. The contributions vary from pipeline sabotage analysis in Iraq to GIS studies about groundwater vulnerability in Gaza Strip, from Population Monitoring in Zimbabwe to Post-Conflict Urban Reconstruction Assessments and many more.
Part III focuses on the research and development of image processing methods and Tools. The themes range from SAR interferometry for the measurement of Surface Displacement to Robust Satellite Techniques for monitoring natural hazards like volcanoes and earthquakes. Further subjects are the 3D detection of buildings in VHR imagery or texture analysis techniques on time series of satellite images with variable illumination and many other more.
The report closes with Part IV. In the chapter ¿The Way Forward¿ a review on four years of integrated work is done. Challenges and achievements during this period are depicted. It ends with an outlook about a possible way forward for integrated European security research.JRC.G.2-Support to external securit