Bio-Medical Instrumentation (UEI608) Lecture Notes PDF

BIO-MEDICAL INSTRUMENTATION (UEI608) Lecture: Course Introduction By Dr. Deepti Mittal (Associate Professor) Department of Electrical & Instrumentation Engineering Thapar Institute of Engineeri...

BIO-MEDICAL INSTRUMENTATION (UEI608) Lecture: Course Introduction By Dr. Deepti Mittal (Associate Professor) Department of Electrical & Instrumentation Engineering Thapar Institute of Engineering & Technology Patiala, India Biomedical Instrumentation Biomedical Instrumentation presents a course of study and applications covering the basic principles of medical and biological instrumentation, as well as the typical features of its design and construction. Blood Pressure Blood Glucose Cardiac Monitor Defibrillator Monitor Monitor Biomedical Instrumentation - deals with the application of the engineering concepts and principles to solve clinical problems in medical care and surgery. - focuses on the devices and mechanics used to measure, evaluate, and treat biological systems. Hearing aids Artificial heart Medical equipment Students can become Biomedical Engineer, Biomedical Application Specialist, Medical Device Entrepreneur, Biomedical Scientist, Equipment Specialist, Clinical Engineer and an Academician in Biomedical Engineering. Measuring Instruments Pulse Oximeter Blood gas analyser Cardiac output measurement Blood flow measurement device Telemetry systems Pulmonary Function Analyser Spectrophotometry Blood cell counter Recording Instruments Electromyograph Potentiometric Recorder Electrocardiograph Digital Stethoscope Electroencephalograph Phonocardiograph Monitoring Instruments Ambulatory monitoring Instrument Arrhythmia Monitoring Instrument Bedside patient monitoring system Wearable cardiac Monitor Foetal Monitoring Instrument Modern Imaging Systems Dental X-Ray Computed Tomography X-Ray Thermal imaging system Magnetic Resonance Imaging System Ultrasound Therapeutic Equipment Cardiac Pacemakers Cardiac Defibrillators Haemodialysis Machines Surgical Diathermy Machine Ventilator Microwave Diathermy Worldwide the medical instrumentation and device industry is worth more than 100 billion US dollars annually. A number of multinational companies, including Boston Scientific, Medtronic, Abbot Medical Devices, Johnson & Johnson and Novo Nordisk, have a major focus on the development, sales and distribution of several broad classes of medical devices. The five largest areas of medical device revenue are orthopaedics, ophthalmology, cardiology, audiology and surgery. Hundreds of smaller companies, including new start-ups, concentrate on more specialized parts of the market. In a medical instrumentation system, the main function is to measure or determine the presence of some physical quantity that may be useful for diagnostic purposes. A knowledge of the structure of the living body and its function is essential for understanding the functioning of most of the medical instruments. The science of structure of the body is known as “Anatomy” and that of its function, “Physiology”. Physiological Systems of the body Human body is a complex engineering marvel, which contains various types of systems such as electrical, mechanical, hydraulic, pneumatic, chemical and thermal etc. These systems communicate internally with each other and also with an external environment. By means of a multi-level control system and communications network, the individual systems enable the human body to perform useful tasks, sustain life and reproduce itself. Physiological Systems of the body Physiological Systems The Cardiovascular System Physiological Systems The Circulatory System Physiological Systems The Respiratory System Physiological Systems The Nervous System The Cardiovascular System ❑ A complex closed hydraulic system ❑ Performs transportation of oxygen, carbon dioxide, numerous chemical compounds and the blood cells ❑ the heart is divided into right and left parts ❑ Each part has two chambers called atrium and ventricle ❑ The heart has four valves ❑ Tricuspid valve or right atrio-ventricular valve—between right atrium and ventricle ❑ Bicuspid Mitral or left atrio-ventricular valve—between left atrium and left ventricle. ❑ Aortic valve—between left ventricle and aorta ❑ Pulmonary valve—at the right ventricle The Cardiovascular System ❑ The heart wall consists of three layers ❑ The pericardium, which is the outer layer of the heart ❑ It keeps the outer surface moist and prevents friction as the heart beats ❑ The myocardium is the middle layer of the heart ❑ It is the main muscle of the heart, which is made up of short cylindrical fibres ❑ This muscle is automatic in action, contracting and relaxing rythmically throughout life ❑ The endocardiumis the inner layer of the heart ❑ It provides smooth lining for the blood to flow The Circulatory System ❑ The circulatory system consists of four major components: ❑ The Heart: Thanks to consistent pumping, the heart keeps the circulatory system working at all times. ❑ Arteries: Arteries carry oxygen-rich blood away from the heart and where it needs to go. ❑ Veins: Veins carry deoxygenated blood to the heart where it is directed to the lungs to receive oxygen ❑ Blood: Blood is the transport media and transports hormones, nutrients, oxygen, antibodies, and other important things needed to keep the body healthy. ❑ The circulatory system works thanks to constant pressure from the heart and valves throughout the body. This pressure ensures that veins carry blood to the heart and arteries transport it away from the heart. The Circulatory System ❑ There are three different types of circulation that occur regularly in the body: ❑ Pulmonary circulation: This part of the cycle carries oxygen- depleted blood away from the heart, to the lungs, and back to the heart. ❑ Systemic circulation: This is the part that carries oxygenated blood away from the heart and to other parts of the body. ❑ Coronary circulation: This type of circulation provides the heart with oxygenated blood so it can function properly. The Respiratory System ❑ Airways deliver air to lungs ❑ Airways includes: Mouth and nose: pull air from outside into respiratory system. Sinuses: Hollow areas between the bones in your head that help regulate the temperature and humidity of the air you inhale. Pharynx (throat): Tube that delivers air from your mouth and nose to the trachea (windpipe). Trachea: Passage connecting your throat and lungs. Bronchial tubes: Tubes at the bottom of your windpipe that connect into each lung. Lungs: Two organs that remove oxygen from the air and pass it into your blood. Alveoli: Tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place. Bronchioles: Small branches of the bronchial tubes that lead to the alveoli. The Respiratory System Muscles and bones help move the air you inhale into and out of your lungs. Some of the bones and muscles in the respiratory system include Diaphragm: Muscle that helps your lungs pull in air and push it out Ribs: Bones that surround and protect your lungs and heart The Nervous System ❑ The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. Together, these organs are responsible for the control of the body and communication among its parts. ❑ The nervous system comprises the central nervous system, consisting of the brain and spinal cord, and the peripheral nervous system, consisting of the cranial, spinal, and peripheral nerves, together with their motor and sensory endings. END BIO-MEDICAL INSTRUMENTATION (UEI608) Lecture: Bio-Signals and Man-Instrument System By Dr. Deepti Mittal (Associate Professor) Department of Electrical & Instrumentation Engineering Thapar Institute of Engineering & Technology Patiala, India Biomedical signals Sources of biomedical signals signals which are used primarily for extracting information on a biological system under investigation. The process of extracting information could be as simple as feeling the pulse of a person on the wrist or as complex as analyzing the structure of internal soft tissues by an ultrasound scanner. Biomedical signals originate from a variety of sources. Bioelectric Signals: - generated by nerve cells and muscle cells. - basic source is the cell membrane potential which under certain conditions may be excited to generate an action potential. - The electric field generated by the action of many cells constitutes the bioelectric signal. - common examples: ECG (electrocardiographic) and EEG (electroencephalographic) signals. Bioacoustic Signals: - acoustic signals created by many biomedical phenomena provides information about the underlying phenomena. - Examples: flow of blood in the heart, through the heart’s valves and flow of air through the upper and lower airways and in the lungs which generate typical acoustic signal Biomechanical Signals: - originate from some mechanical function of the biological system. - include all types of motion and displacement signals, pressure and flow signals etc. - Example: the movement of the chest wall in accordance with the respiratory activity. Biochemical Signals: - obtained as a result of chemical measurements from the living tissue or from samples analyzed in the laboratory. - Examples: partial pressure of carbon dioxide (pCO2), partial pressure of oxygen (pO2) and concentration of various ions in the blood. Biomagnetic Signals: - Extremely weak magnetic fields are produced by various organs such as the brain, heart and lungs. - provides information which is not available in other types of bio-signals such bio-electric signals. - Example: magneto-encephalograph signal from the brain. Bio-optical Signals: - result of optical functions of the biological systems, occurring either naturally or induced by the measurement process. - Example, blood oxygenation, estimated by measuring the transmitted/back scattered light from a tissue at different wavelengths. Bio-impedance Signals: - The impedance of the tissue is a source of important information concerning its composition, blood distribution and blood volume etc. - Example: the measurement of galvanic skin resistance. - Also obtained by injecting sinusoidal current in the tissue and measuring the voltage drop generated by the tissue impedance. - Example: the measurement of respiration rate based on bio-impedance technique. These systems and signals represent a classic exercise in engineering that involves the measurement of output/ outputs from an unknown system as they are affected by various combinations of inputs. The object is to learn the nature and characteristics of the system. This unknown system (a black box) may have a variety of configurations for a given combination of inputs and outputs. The end product of such an exercise is usually a set of input-output equations intended to define the internal functions of the box. These functions may be relatively simple or extremely complex. Introduction of Man- Machine (Instrumentation) System It is the human being and Instrumentation combined. It involves the measurements of OUTPUTS from an Unknown system as they are affected by various combinations of INPUTS. One of the most complex black box is living organism, especially the human being… Human body as a Black Box Within this box can be found electrical, mechanical, acoustical, thermal, chemical, optical, hydraulic, pneumatic, and many other types of systems, all interacting with each other. Human body is a Bio-Chemico-Physico-Electro-Thermo-Hydraulico-Pneumatico-Megneto mechanically engineered machine, which runs automatically through the vital force, which is called bio energy. It also contains a powerful computer, several types of communication systems, and a great variety of control systems. To further complicate the situation, upon attempting to measure the inputs and outputs, an engineer would soon learn that none of the input-output relationships is deterministic. That is, repeated application of a given set of input values will not always produce the same output values. In fact, many of the outputs seem to show a wide range of responses to a given set of inputs, depending on some seemingly relevant conditions, whereas others appear to be completely random and totally unrelated to any of the inputs. The living black box presents other problems, too. Many of the important variables to be measured are not readily accessible to measuring devices. The result is that some key relationships cannot be determined or that less accurate substitute measures must be used. Furthermore, there is a high degree of interaction among the variables in this box. Thus, it is often impossible to hold one variable constant while measuring the relationship between two others. In fact, it is sometimes difficult to determine which are the inputs and which are the outputs, for they are never labeled and almost inevitably include one or more feedback paths. The situation is made even worse by the application of the measuring device itself, which often affects the measurements to the extent that they may not represent normal conditions reliably. BIO-MEDICAL INSTRUMENTATION (UEI608) Lecture: Man-Instrumentation System By Dr. Deepti Mittal (Associate Professor) Department of Electrical & Instrumentation Engineering Thapar Institute of Engineering & Technology Patiala, India At first glance an assignment to measure and analyze the variables in a living black box would probably be labeled 'impossible'' by most engineers; yet this is the very problem facing those in the medical field who attempt to measure and understand the internal relationships of the human body. The function of medical instrumentation is to aid the medical clinician and researcher in devising ways of obtaining reliable and meaningful measurements from a living human being. Still other problems are associated with such measurements: the process of measuring must not in any way endanger the life of the person on whom the measurements are being made, and it should not require the subject to endure undue pain, discomfort, or any other undesirable conditions. This means that many of the measurement techniques normally employed in the instrumentation of non-living systems cannot be applied in the instrumentation of humans. Additional factors that add to the difficulty of obtaining valid measurements are (1) safety considerations, (2) the environment of the hospital in which these measurements are performed, (3) the medical personnel usually involved in the measurements, and (4) occasionally even ethical and legal considerations. Because special problems are encountered in obtaining data from living organisms, especially human beings, and because of the large amount of interaction between the instrumentation system and the subject being measured, it is essential that the person on whom measurements are made be considered an integral part of the instrumentation system. In other words, in order to make sense out of the data to be obtained from the black box (the human organism), the internal characteristics of the black box must be considered in the design and application of any measuring instruments. Consequently, the overall system, which includes both the human organism and the instrumentation required for measurement of the human is called the man-instrument system. Instrumentation system: the set of instruments and equipment utilized in the measurement of one or more characteristics or phenomena, plus the presentation of information obtained from those measurements in a form that can be read and interpreted by man. The basic objectives of any instrumentation system generally fall into one of the following major categories: 1. Information gathering: In this setting, the characteristics of the measurements may not be known in advance. 2. Diagnosis: Measurements are made to help in the detection and, the correction of some malfunction of the system being measured (troubleshooting equipment). 3. Evaluation: Measurements are used to determine the ability of a system to meet its functional requirements (proof- of-performance) or (quality control). 4. Monitoring: Instrumentation is used to monitor some process or operation in order to obtain continuous or periodic information about the state of the system being measured. 5. Control: Instrumentation is sometimes used to automatically control the operation of a system based on changes in one or more of the internal parameters or in the output of the system. Biomedical instrumentation can generally be classified into two major types: clinical and research. Clinical instrumentation: basically devoted to the diagnosis, care, and treatment of patients, Research instrumentation: the search for new knowledge pertaining to the various systems that compose the human organism. clinical instruments are generally designed to be more rugged and easier to use. Emphasis is placed on obtaining a limited set of reliable measurements from a large group of patients and on providing the physician with enough information to permit him to make clinical decisions. On the other hand, research instrumentation is normally more complex, more specialized, and often designed to provide a much higher degree of accuracy, resolution, and so on. Clinical instruments are used by the physician or nurse, whereas research instruments are generally operated by skilled technologists whose primary training is in the operation of such instruments. Measurements in which biomedical instrumentation is employed can also be divided into two categories: in vivo and in vitro. An in vivo measurement is one that is made on or within the living organism itself. An example would be a device inserted into the bloodstream to measure the pH of the blood directly. An example of an in vitro measurement would be the measurement of the pH of a sample of blood that has been drawn from a patient. The basic components of this system are essentially the same as in any instrumentation system. The only real difference is in having a living human being as the subject. The Subject The subject is the human being on whom the measurements are made. Since it is the subject who makes this system different from other instrumentation systems, the major physiological systems that constitute the human body are need to understood Stimulus In many measurements, the response to some form of external stimulus is required. The instrumentation used to generate and present this stimulus to the subject is a vital part of the man- instrument system whenever responses are measured. The stimulus may be visual (e.g., a flash of light), auditory (e.g., a tone), tactile (e.g., a blow to the Achilles tendon), or direct electrical stimulation of some part of the nervous system. The Transducer In general, a transducer is defined as a device capable of converting one form of energy or signal to another. In the man-instrument system, each transducer is used to produce an electric signal that is an analog of the phenomenon being measured. The transducer may measure temperature, pressure, flow, or any of the other variables that can be found in the body, but its output is always an electric signal. two or more transducers may be used simultaneously to obtain relative variations between phenomena. Signal-Conditioning Equipment The part of the instrumentation system that amplifies, modifies, or in any other way changes the electric output of the transducer is called signal conditioning (or sometimes signal-processing) equipment. Signal-conditioning equipment is also used to combine or relate the outputs of two or more transducers. Thus, for each item of signal-conditioning equipment, both the input and the output are electric signals, although the output signal is often greatly modified with respect to the input. In essence, then, the purpose of the signal-conditioning equipment is to process the signals from the transducers in order to satisfy the functions of the system and to prepare signals suitable for operating the display or recording equipment that follows.  Display Equipment To be meaningful, the electrical output of the signal-conditioning equipment must be converted into a form that can be perceived by one of man's senses and that can convey the information obtained by the measurement in a meaningful way. The input to the display device is the modified electric signal from the signal-conditioning equipment. Its output is some form of visual, audible, or possibly tactile information. In the man-instrumentation system, the display equipment may include a graphic pen recorder that produces a permanent record of the data. Recording, Data-Processing, and Transmission Equipment It is often necessary, or at least desirable, to record the measured information for possible later use or to transmit it from one location to another, whether across the hall of the hospital or halfway around the world. Equipment for these functions is often a vital part of the man-instrument system. Also, where automatic storage or processing of data is required, or where computer control is employed, an on- line analog or digital computer may be part of the instrumentation system It should be noted that the term recorder is used in two different contexts in biomedical instrumentation. A graphic pen recorder is actually a display device used to produce a paper record of analog waveforms, whereas the recording equipment referred to in this paragraph includes devices by which data can be recorded for future playback, as in a magnetic tape recorder. Control Devices Where it is necessary or desirable to have automatic control of the stimulus, transducers, or any other part of the man-instrument system, a control system is incorporated. This system usually consists of a feedback loop in which part of the output from the signal-conditioning or display equipment is used to control the operation of the system in some way. END