(BQ) Part 1 The biomedical engineering handbook Medical devices and systems has contents: Digital biomedical signal acquisition and processing, higher order spectral analysis, neural networks in biomedical signal processing, computed tomography,...and other contents.
The Biomedical Engineering Handbook Third Edition Medical Devices and Systems Bronz: “2122_c000” — 2006/2/24 — 11:31 — page ii — #2 The Electrical Engineering Handbook Series Series Editor Richard C Dorf University of California, Davis Titles Included in the Series The Handbook of Ad Hoc Wireless Networks, Mohammad Ilyas The Avionics Handbook, Cary R Spitzer The Biomedical Engineering Handbook, Third Edition, Joseph D Bronzino The Circuits and Filters Handbook, Second Edition, Wai-Kai Chen The Communications Handbook, Second Edition, Jerry Gibson The Computer Engineering Handbook, Vojin G Oklobdzija The Control Handbook, William S Levine The CRC Handbook of Engineering Tables, Richard C Dorf The Digital Signal Processing Handbook, Vijay K Madisetti and Douglas Williams The Electrical Engineering Handbook, Third Edition, Richard C Dorf The Electric Power Engineering Handbook, Leo L Grigsby The Electronics Handbook, Second Edition, Jerry C Whitaker The Engineering Handbook, Third Edition, Richard C Dorf The Handbook of Formulas and Tables for Signal Processing, Alexander D Poularikas The Handbook of Nanoscience, Engineering, and Technology, William A Goddard, III, Donald W Brenner, Sergey E Lyshevski, and Gerald J Iafrate The Handbook of Optical Communication Networks, Mohammad Ilyas and Hussein T Mouftah The Industrial Electronics Handbook, J David Irwin The Measurement, Instrumentation, and Sensors Handbook, John G Webster The Mechanical Systems Design Handbook, Osita D.I Nwokah and Yidirim Hurmuzlu The Mechatronics Handbook, Robert H Bishop The Mobile Communications Handbook, Second Edition, Jerry D Gibson The Ocean Engineering Handbook, Ferial El-Hawary The RF and Microwave Handbook, Mike Golio The Technology Management Handbook, Richard C Dorf The Transforms and Applications Handbook, Second Edition, Alexander D Poularikas The VLSI Handbook, Wai-Kai Chen The Biomedical Engineering Handbook Third Edition Edited by Joseph D Bronzino Biomedical Engineering Fundamentals Medical Devices and Systems Tissue Engineering and Artificial Organs The Biomedical Engineering Handbook Third Edition Medical Devices and Systems Edited by Joseph D Bronzino Trinity College Hartford, Connecticut, U.S.A Boca Raton London New York A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc 2122_Discl.fm Page Wednesday, December 14, 2005 4:52 PM Published in 2006 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2006 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group No claim to original U.S Government works Printed in the United States of America on acid-free paper 10 International Standard Book Number-10: 0-8493-2122-0 (Hardcover) International Standard Book Number-13: 978-0-8493-2122-1 (Hardcover) Library of Congress Card Number 2005056892 This book contains information obtained from authentic and highly regarded sources Reprinted material is quoted with permission, and sources are indicated A wide variety of references are listed Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use No part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers For permission to photocopy or use material electronically from this work, please access www.copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400 CCC is a not-for-profit organization that provides licenses and registration for a variety of users For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe Library of Congress Cataloging-in-Publication Data Medical devices and systems / edited by Joseph D Bronzino p cm (The electrical engineering handbook series) Includes bibliographical references and index ISBN 0-8493-2122-0 Medical instruments and apparatus Handbooks, manuals, etc I Bronzino, Joseph D., 1937- II Title III Series R856.15.B76 2006 610.28 dc22 2005056892 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com Taylor & Francis Group is the Academic Division of Informa plc and the CRC Press Web site at http://www.crcpress.com Introduction and Preface During the past five years since the publication of the Second Edition — a two-volume set — of the Biomedical Engineering Handbook, the field of biomedical engineering has continued to evolve and expand As a result, this Third Edition consists of a three volume set, which has been significantly modified to reflect the state-of-the-field knowledge and applications in this important discipline More specifically, this Third Edition contains a number of completely new sections, including: • • • • • Molecular Biology Bionanotechnology Bioinformatics Neuroengineering Infrared Imaging as well as a new section on ethics In addition, all of the sections that have appeared in the first and second editions have been significantly revised Therefore, this Third Edition presents an excellent summary of the status of knowledge and activities of biomedical engineers in the beginning of the 21st century As such, it can serve as an excellent reference for individuals interested not only in a review of fundamental physiology, but also in quickly being brought up to speed in certain areas of biomedical engineering research It can serve as an excellent textbook for students in areas where traditional textbooks have not yet been developed and as an excellent review of the major areas of activity in each biomedical engineering subdiscipline, such as biomechanics, biomaterials, bioinstrumentation, medical imaging, etc Finally, it can serve as the “bible” for practicing biomedical engineering professionals by covering such topics as a historical perspective of medical technology, the role of professional societies, the ethical issues associated with medical technology, and the FDA process Biomedical engineering is now an important vital interdisciplinary field Biomedical engineers are involved in virtually all aspects of developing new medical technology They are involved in the design, development, and utilization of materials, devices (such as pacemakers, lithotripsy, etc.) and techniques (such as signal processing, artificial intelligence, etc.) for clinical research and use; and serve as members of the health care delivery team (clinical engineering, medical informatics, rehabilitation engineering, etc.) seeking new solutions for difficult health care problems confronting our society To meet the needs of this diverse body of biomedical engineers, this handbook provides a central core of knowledge in those fields encompassed by the discipline However, before presenting this detailed information, it is important to provide a sense of the evolution of the modern health care system and identify the diverse activities biomedical engineers perform to assist in the diagnosis and treatment of patients Evolution of the Modern Health Care System Before 1900, medicine had little to offer the average citizen, since its resources consisted mainly of the physician, his education, and his “little black bag.” In general, physicians seemed to be in short Bronz: “2122_c000” — 2006/2/24 — 11:31 — page v — #5 supply, but the shortage had rather different causes than the current crisis in the availability of health care professionals Although the costs of obtaining medical training were relatively low, the demand for doctors’ services also was very small, since many of the services provided by the physician also could be obtained from experienced amateurs in the community The home was typically the site for treatment and recuperation, and relatives and neighbors constituted an able and willing nursing staff Babies were delivered by midwives, and those illnesses not cured by home remedies were left to run their natural, albeit frequently fatal, course The contrast with contemporary health care practices, in which specialized physicians and nurses located within the hospital provide critical diagnostic and treatment services, is dramatic The changes that have occurred within medical science originated in the rapid developments that took place in the applied sciences (chemistry, physics, engineering, microbiology, physiology, pharmacology, etc.) at the turn of the century This process of development was characterized by intense interdisciplinary cross-fertilization, which provided an environment in which medical research was able to take giant strides in developing techniques for the diagnosis and treatment of disease For example, in 1903, Willem Einthoven, a Dutch physiologist, devised the first electrocardiograph to measure the electrical activity of the heart In applying discoveries in the physical sciences to the analysis of the biologic process, he initiated a new age in both cardiovascular medicine and electrical measurement techniques New discoveries in medical sciences followed one another like intermediates in a chain reaction However, the most significant innovation for clinical medicine was the development of x-rays These “new kinds of rays,” as their discoverer W.K Roentgen described them in 1895, opened the “inner man” to medical inspection Initially, x-rays were used to diagnose bone fractures and dislocations, and in the process, x-ray machines became commonplace in most urban hospitals Separate departments of radiology were established, and their influence spread to other departments throughout the hospital By the 1930s, x-ray visualization of practically all organ systems of the body had been made possible through the use of barium salts and a wide variety of radiopaque materials X-ray technology gave physicians a powerful tool that, for the first time, permitted accurate diagnosis of a wide variety of diseases and injuries Moreover, since x-ray machines were too cumbersome and expensive for local doctors and clinics, they had to be placed in health care centers or hospitals Once there, x-ray technology essentially triggered the transformation of the hospital from a passive receptacle for the sick to an active curative institution for all members of society For economic reasons, the centralization of health care services became essential because of many other important technological innovations appearing on the medical scene However, hospitals remained institutions to dread, and it was not until the introduction of sulfanilamide in the mid-1930s and penicillin in the early 1940s that the main danger of hospitalization, that is, cross-infection among patients, was significantly reduced With these new drugs in their arsenals, surgeons were able to perform their operations without prohibitive morbidity and mortality due to infection Furthermore, even though the different blood groups and their incompatibility were discovered in 1900 and sodium citrate was used in 1913 to prevent clotting, full development of blood banks was not practical until the 1930s, when technology provided adequate refrigeration Until that time, “fresh” donors were bled and the blood transfused while it was still warm Once these surgical suites were established, the employment of specifically designed pieces of medical technology assisted in further advancing the development of complex surgical procedures For example, the Drinker respirator was introduced in 1927 and the first heart-lung bypass in 1939 By the 1940s, medical procedures heavily dependent on medical technology, such as cardiac catheterization and angiography (the use of a cannula threaded through an arm vein and into the heart with the injection of radiopaque dye) for the x-ray visualization of congenital and acquired heart disease (mainly valve disorders due to rheumatic fever) became possible, and a new era of cardiac and vascular surgery was established Following World War II, technological advances were spurred on by efforts to develop superior weapon systems and establish habitats in space and on the ocean floor As a by-product of these efforts, the Bronz: “2122_c000” — 2006/2/24 — 11:31 — page vi — #6 development of medical devices accelerated and the medical profession benefited greatly from this rapid surge of technological finds Consider the following examples: Advances in solid-state electronics made it possible to map the subtle behavior of the fundamental unit of the central nervous system — the neuron — as well as to monitor the various physiological parameters, such as the electrocardiogram, of patients in intensive care units New prosthetic devices became a goal of engineers involved in providing the disabled with tools to improve their quality of life Nuclear medicine — an outgrowth of the atomic age — emerged as a powerful and effective approach in detecting and treating specific physiologic abnormalities Diagnostic ultrasound based on sonar technology became so widely accepted that ultrasonic studies are now part of the routine diagnostic workup in many medical specialties “Spare parts” surgery also became commonplace Technologists were encouraged to provide cardiac assist devices, such as artificial heart valves and artificial blood vessels, and the artificial heart program was launched to develop a replacement for a defective or diseased human heart Advances in materials have made the development of disposable medical devices, such as needles and thermometers, as well as implantable drug delivery systems, a reality Computers similar to those developed to control the flight plans of the Apollo capsule were used to store, process, and cross-check medical records, to monitor patient status in intensive care units, and to provide sophisticated statistical diagnoses of potential diseases correlated with specific sets of patient symptoms Development of the first computer-based medical instrument, the computerized axial tomography scanner, revolutionized clinical approaches to noninvasive diagnostic imaging procedures, which now include magnetic resonance imaging and positron emission tomography as well A wide variety of new cardiovascular technologies including implantable defibrillators and chemically treated stents were developed 10 Neuronal pacing systems were used to detect and prevent epileptic seizures 11 Artificial organs and tissue have been created 12 The completion of the genome project has stimulated the search for new biological markers and personalized medicine The impact of these discoveries and many others has been profound The health care system of today consists of technologically sophisticated clinical staff operating primarily in modern hospitals designed to accommodate the new medical technology This evolutionary process continues, with advances in the physical sciences such as materials and nanotechnology, and in the life sciences such as molecular biology, the genome project and artificial organs These advances have altered and will continue to alter the very nature of the health care delivery system itself Biomedical Engineering: A Definition Bioengineering is usually defined as a basic research-oriented activity closely related to biotechnology and genetic engineering, that is, the modification of animal or plant cells, or parts of cells, to improve plants or animals or to develop new microorganisms for beneficial ends In the food industry, for example, this has meant the improvement of strains of yeast for fermentation In agriculture, bioengineers may be concerned with the improvement of crop yields by treatment of plants with organisms to reduce frost damage It is clear that bioengineers of the future will have a tremendous impact on the qualities of human life The potential of this specialty is difficult to imagine Consider the following activities of bioengineers: • Development of improved species of plants and animals for food production • Invention of new medical diagnostic tests for diseases Bronz: “2122_c000” — 2006/2/24 — 11:31 — page vii — #7 26-30 Medical Devices and Systems [27] Gamagami P Indirect signs of breast cancer: angiogreneis study In Atlas of Mammography Blackwell Science, Cambridge, MA, pp 231–226, 1996 [28] Guidi A.J and Schnitt S.J Angiogenesis in preinvasive lesions of the breast Breast J 2, 364–369, 1996 [29] Anbar M Hyperthermia of the cancerous breast: analysis of mechanism Cancer Lett 84, 23–29, 1994 [30] Anbar M Breast cancer In Quantitative Dynamic Telethermometry in Medical Diagnosis and Management CRC Press, Ann Arbor, MI, pp 84–94, 1994 [31] Parisky H.R., Sard A et al Efficacy of computerized infrared imagng analysis to evaluate mammographically suspicious lesions Am J Radiol 180, 263–272, 2003 [32] Sickles E.A Mammographic features of “early” breast cancer Am J Roentgenol 143, 461, 1984 [33] Thomas D.B., Gao D.L., Self S.G et al Randomized trial of breast self-examination in Shanghai: methodology and preliminary results J Natl Cancer Inst 5, 355–365, 1997 [34] Elmore J.G., Wells C.F., Carol M.P.H et al Variability in radiologists interpretation of mammograms N Engl J Med 331, 99–104, 1993 [35] Boyd N.F., Byng J.W., Jong R.A et al Quantitative classification of mammographic densities and breast cancer risk J Natl Cancer Inst 87, 670–675, 1995 [36] Laya M.B Effect on estrogen replacement therapy on the specificity and sensibility of screening mammography J Natl Cancer Inst 88, 643–649, 1996 [37] Singletary S.E., McNeese M.D., and Hortobagyi G.N Feasibility of breast-conservation surgery after induction chemotherapy for locally advanced breast carcinoma Cancer 69, 2849–2852, 1992 [38] Jansson T., Westlin J.E., Ahlstrom H et al Position emission tomography studies in patients with locally advanced and/or metastatic breast cancer: a method for early therapy evaluation? J Clin Oncol 13, 1470–1477, 1995 [39] Hendry J Combined positron emission tomography and computerized tomography Whole body imaging superior to MRI in most tumor staging JAMA 290, 3199–3206, 2003 [40] Keyserlingk J.R., Ahlgren P.D., Yu E., and Belliveau N Infrared imaging of the breast: initial reappraisal using high-resolution digital technology in 100 successive cases of stage I and II breast cancer Breast J 4, 245–251, 1998 [41] Keyserlingk J.R., Yassa, M., Ahlgren, P., and Belliveau N Tozzi Ville Marie Oncology Center and St Mary’s Hospital, Montreal, Canada D Preliminary Evaluation of Digital Functional Infrared Imaging to Reflect Preoperative Chemohormonotherapy-Induced Changes in Neoangiogenesis in Patients with Locally Advanced Breast Cancer European Oncology Society, Milan, Italy, September 2001 [42] Berg et al Tumor type and breast profile determine value of mammography, ultrasound and MR Radiology 233, 830–849, 2004 [43] Oestreicher et al Breast exam and mammography Am J Radiol 151, 87–96, 2004 [44] Mendelson, Berg et al Ultrasound in the operated breast; presented at the 2004 RSNA Chicago, November 2005 Bronz: “2122_c026” — 2006/2/9 — 21:54 — page 30 — #30 27 Detecting Breast Cancer from Thermal Infrared Images by Asymmetry Analysis 27.1 Introduction 27-1 Measuring the Temperature of Human Body • Metabolic Activity of Human Body and Cancer Cells • Early Detection of Breast Cancer Hairong Qi The University of Tennessee Phani Teja Kuruganti Oak Ridge National Laboratory Wesley E Snyder North Carolina State University 27.2 Asymmetric Analysis in Breast Cancer Detection 27-4 Automatic Segmentation • Asymmetry Identification by Unsupervised Learning • Asymmetry Identification Using Supervised Learning Based on Feature Extraction 27.3 Conclusions 27-12 References 27-13 One of the popular methods for breast cancer detection is to make comparisons between contralateral images When the images are relatively symmetrical, small asymmetries may indicate a suspicious region In thermal infrared (IR) imaging, asymmetry analysis normally needs human intervention because of the difficulties in automatic segmentation In order to provide a more objective diagnostic result, we describe an automatic approach to asymmetry analysis in thermograms It includes automatic segmentation and supervised pattern classification Experiments have been conducted based on images provided by Elliott Mastology Center (Inframetrics 600M camera) and Bioyear, Inc (Microbolometer uncooled camera) 27.1 Introduction The application of IR imaging in breast cancer study starts as early as 1961 when Williams and Handley first published their results in the Lancet [1] However, the premature use of the technology and its poorly controlled introduction into breast cancer detection in the 1970s have led to its early demise [2] IR-based diagnosis was criticized as generating a higher false-positive rate than mammography, and thus was not recommended as a standard modality for breast cancer detection Therefore, despite its deployment in 27-1 Bronz: “2122_c027” — 2006/2/9 — 21:55 — page — #1 27-2 Medical Devices and Systems many areas of industry and military, IR usage in medicine has declined [3] Three decades later, several papers and studies have been published to reappraise the use of IR in medicine [2,3] for the following three reasons (1) We have greatly improved IR technology New generations of IR cameras have been developed with much enhanced accuracy; (2) We have much better capabilities in image processing Advanced techniques including image enhancement, restoration, and segmentation have been effectively used in processing IR images; and (3) We have a deeper understanding of the patho-physiology of heat generation The main objective of this work is to evaluate the viability of IR imaging as a noninvasive imaging modality for early detection of breast cancer so that it can be performed both on the symptomatic and the asymptomatic patient and can thus be used as a complement to traditional mammography This report summarizes how the identification of the asymmetry can be automated using image segmentation, feature extraction, and pattern recognition techniques We investigate different features that contribute the most toward the detection of asymmetry This kind of approach helps reduce the false-positive rate of the diagnosis and increase chances of disease cure and survival 27.1.1 Measuring the Temperature of Human Body Temperature is a long established indicator of health The Greek physician, Hippocrates, wrote in 400 b.c “In whatever part of the body excess of heat or cold is felt, the disease is there to be discovered” [4] The ancient Greeks immersed the body in wet mud and the area that dried more quickly, indicating a warmer region, was considered the diseased tissue The use of hands to measure the heat emanating from the body remained well into the 16th and the 17th centuries It wasn’t until Galileo, who made a thermoscope from a glass tube, that some form of temperature sensing device was developed, but it did not have a scale It is Fahrenheit and later Celsius who have fixed the temperature scale and proposed the present day clinical thermometer The use of liquid crystals is another method of displaying skin temperature Cholesteric esters can have the property of changing colors with temperature and this was established by Lehmann in 1877 It was involved in use of elaborative panels that encapsulated the crystals and were applied to the surface of the skin, but due to large area of contact, they affected the temperature of the skin All the methods discussed above are contact based Major advances over the past 30 years have been with IR thermal imaging The astronomer, Sir William Herschel, in Bath, England discovered the existence of IR radiation by trying to measure the heat of the separate colors of the rainbow spectrum cast on a table in the darkened room He found that the highest temperature was found beyond the red end of the spectrum He reported this to the Royal society as Dark Heat in 1800, which eventually has been turned the IR portion of the spectrum IR radiation occupies the region between visible and microwaves All objects in the universe emit radiations in the IR region of the spectra as a function of their temperature As an object gets hotter, it gives off more intense IR radiation, and it radiates at a shorter wavelength [3] At moderate temperatures (above 200◦ F), the intensity of the radiation gets high enough that the human body can detect that radiation as heat At sufficiently high temperatures (above 1200◦ F), the intensity gets high enough and the wavelength gets short enough that the radiation crosses over the threshold to the red end of the visible light spectrum The human eye cannot detect IR rays, but they can be detected by using the thermal IR cameras and detectors 27.1.2 Metabolic Activity of Human Body and Cancer Cells Metabolic process in a cell can be briefly defined as the sum total of all the enzymatic reactions occurring in the cell It can be further elaborated as a highly coordinated, purposeful activity in which many sets of interrelated multienzyme systems participate, exchanging both matter and energy between the cell and its environment Metabolism has four specific functions (1) To obtain chemical energy from the fuel molecules; (2) To convert exogenous nutrients into the building blocks or precursor of macromolecular cell components; (3) To assemble such building blocks into proteins, nucleic acids, lipids, and Bronz: “2122_c027” — 2006/2/9 — 21:55 — page — #2 Detecting Breast Cancer from Thermal Infrared Images 27-3 other cell components; and (4) To form and degrade biomolecules required in specialized functions of the cell Metabolism can be divided into two major phases, Catabolism and Anabolism Catabolism is the degradative phase of metabolism in which relatively large and complex nutrient molecules (carbohydrates, lipids, and proteins) are degraded to yield smaller, simpler molecules such as lactic acid, acetic acid, CO2 , ammonia, or urea Catabolism is accompanied by conservation of some of the energy of the nutrient in the form of phosphate bond energy of adenosine triphosphate (ATP) Conversely, anabolism is the building up phase of metabolism, the enzymatic biosynthesis of such molecular components of cells as the nucleic acids, proteins, lipids, and carbohydrates from their simple building block precursors Biosynthesis of organic molecules from simple precursors requires input of chemical energy, which is furnished by ATP generated during catabolism Each of these pathways is promoted by a sequence of specific enzymes catalyzing consecutive reactions The energy produced by the metabolic pathways is utilized by the cell for its division Cells undergo mitotic cell division, a process in which a single cell divides into many cells and forms tissues, leading further into the development and growth of the multicellular organs When cells divide, each resultant part is a complete relatively small cell Immediately after division the newly formed cells grow rapidly soon reaching the size of the original cell In humans, growth occurs through mitotic cell division with subsequent enlargement and differentiation of the reproduced cells into organs Cancer cells also grow similarly but lose the ability to differentiate into organs So, a cancer may be defined as an actively dividing undifferentiated mass of cells called the “tumor.” Cancer cells result from permanent genetic change in a normal cell triggered by some external physical agents such as chemical agents, x-rays, UV rays, etc They tend to grow aggressively and not obey normal pattern of tissue formation Cancer cells have a distinctive type of metabolism Although they possess all the enzymes required for most of the central pathways of metabolism, cancer cells of nearly all types show an anomaly in the glucose degradation pathway (viz Glycolysis) The rate of oxygen consumption is somewhat below the values given by normal cells However the malignant cells tend to utilize anywhere from to 10 times as much glucose as normal tissue and convert most of it into lactate instead of pyruvate (lactate is a low energy compound whereas pyruvate is a high energy compound) The net effect is that in addition to the generation of ATP in mitochondria from respiration, there is a very large formation of ATP in extramitochondrial compartment from glycolysis The most important effect of this metabolic imbalance in cancer cells is the utilization of a large amount of blood glucose and release of large amounts of lactate into blood The lactate so formed is recycled in the liver to produce blood glucose again Since the formation of blood glucose by the liver requires molecules of ATP whereas breakdown of glucose to lactate produces only ATP molecules, the cancer cells are looked upon as metabolic parasites dependent on the liver for a substantial part of their energy Large masses of cancer cells thus can be a considerable metabolic drain on the host organism In addition to this, the high metabolic rate of cancer cells causes an increase in local temperature as compared to normal cells Local metabolic activity ceases when blood supply is stopped since glycolysis is an oxygen dependent pathway and oxygen is transported to the tissues by the hemoglobin present in the blood; thus, blood supply to these cells is important for them to proliferate The growth of a solid tumor is limited by the blood supply If it were not invaded by capillaries a tumor would be dependent on the diffusion of nutrients from its surroundings and could not enlarge beyond a diameter of a few millimeters Thus, in order to grow further the tumor cells stimulate the blood vessels to form a capillary network that invades the tumor mass This phenomenon is popularly called “angiogenesis,” which is a process of vascularization of a tissue involving the development of new capillary blood vessels Vascularization is a growth of blood vessels into a tissue with the result that the oxygen and nutrient supply is improved Vascularization of tumors is usually a prelude to more rapid growth and often to metastasis (advanced stage of cancer) Vascularization seems to be triggered by angiogenesis factors that stimulate endothelial cell proliferation and migration In the context of this paper the high metabolic rate in the cancer cells and the high density of packaging makes them a key source of heat concentration (since the heat dissipation is low) thus enabling thermal IR imaging as a viable technique to visualize the abnormality Bronz: “2122_c027” — 2006/2/9 — 21:55 — page — #3 27-4 Medical Devices and Systems 27.1.3 Early Detection of Breast Cancer There is a crucial need for early breast cancer detection Research has shown that if detected earlier (tumor size less than 10 mm), the breast cancer patient has an 85% chance of cure as opposed to 10% if the cancer is detected late [5] Different kinds of diagnostic imaging techniques exist in the field of breast cancer detection The most popularly used method presently is x-ray mammography The drawback of this technique is that it is invasive and experts believe that electromagnetic radiation can also be a triggering factor for cancerous growth Because of this, periodic inspection might have a negative effect on the patient’s health Research shows that the mammogram sensitivity is higher for older women (age group 60 to 69 years) at 85% compared with younger women (