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Bio medical instrument – introduction


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This chapter comprises the rudimentary knowledge of the Bio Medical System and its various facets.

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Bio medical instrument – introduction

  1. 1. Bio Medical Instrument – Introduction ER. FARUK BIN POYEN, Asst. Professor DEPT. OF AEIE, UIT, BU, BURDWAN, WB, INDIA
  2. 2. Contents  Introduction  Importance of Bio Medical Instrumentation  Basic Objectives of Biomedical Instrumentation  Anatomy and Physiology of Human Body  Physiological Systems of Human Body  Classification of Bio Medical Instruments  Biomedical Measurements  Sources of Biomedical Signals  Man – Instrumentation System  Constraints in Medical Instrumentation Design  Common Medical Measurements and Instruments 2
  3. 3. Introduction:  Medical instrumentation is a subdivision of biomedical engineering. It emphasizes the measurement of all the variables in the body for the use of diagnosis and all the devices that perform therapy.  It is a cross-disciplinary field of study comprising Engineering Biology Chemistry Medicine  Biomedical Instrumentation is used to take measurements for Monitoring Diagnostic means Therapy  Biomedical instrumentation is generally classified into two major types:  Clinical Instrumentation is devoted to diagnosis, care and treatment of patients.  Research Instrumentation is used primarily in search for new knowledge pertaining to various systems composing the human organism. 3
  4. 4. Importance of Bio Medical Instrumentation:  Studying of Biomedical Instrumentation helps in the following manners: 1. To understand mechanisms, efficiencies & physical changes of various subsystems of the body. 2. To evolve an instrumentation system for diagnosis, therapy and supplementation of body function. 3. To obtain qualitative & quantitative knowledge through different instruments which can help for analysis of disorders, and further the Biomechanics of the cure process. 4. To understand Bio-Chemico-Electro – Thermo- Hydraulico- Pneumatico- Physico- Magnato- Mechano – Dynamic actions and changes of various sub systems of the body in normal states. 5. To understand above actions & changes in various sub systems of the body in the abnormal states i.e. in Pathology. 6. To obtain qualitative & quantitative knowledge of what drug does to the body (Pharmacodynamics) and what body does to the drug. 4
  5. 5. Basic Objectives of the Biomedical Instrumentation  Under mentioned are the principal objectives of a biomedical instrumentation system 1. Information Gathering: Instruments used to measure natural phenomena to aid man in the quest of knowledge about himself. 2. Diagnosis: Measurements are made to help detect and correct malfunction of the system being measured. 3. Evaluation: It is used to determine the ability of a system to meet its functional requirements. 4. Monitoring: It is used to monitor certain situation for continuous or periodic information. 5. Control: It is used to automatically control the operation of a system based on changes in multiple internal parameters. 5
  6. 6. Anatomy and Physiology:  The science of structure of the body is known as Anatomy and that of its functioning is known as Physiology.  Anatomy is further classified as 1. Gross Anatomy: It deals with the study of structure of the organs with naked eyes on dissection. 2. Topographical Anatomy: It deals with the position of the organs in relation to each other. 3. Microscopic Anatomy (Histology): It is the study of the minute structures of the organs by means of microscopy. Cytology is a special field where structure, function and development of the cells are studied.  Physiology is classified into 1. Cell Physiology: The study of the functions of the cells. 2. Pathophysiology: It relates to the pathological (symptoms of diseases) functions of the organs. 3. Circulatory Physiology: The study of blood circulation relating to the functioning of the heart. 4. Respiratory Physiology: It deals with the functioning of the breathing organs. 6
  7. 7. Physiological Systems of the Human Body:  There are several systems working parallel to each other in our body. They are as mentioned below. 1. Cardiovascular System. 2. Respiratory System. 3. Nervous System. 4. Skeletal System. 5. Muscular System. 6. Digestive System. 7. Endocrine System. 8. Exocrine System. 9. Lymphatic System. 10. Urinary System. 11. Reproductive System. 7
  8. 8. System Highlights:  Cardiovascular System: The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH, and maintain homeostasis.  Respiratory System: The respiratory system (called also respiratory apparatus, ventilator system) is a biological system consisting of specific organs and structures used for the process of respiration in an organism. The respiratory system is involved in the intake and exchange of oxygen and carbon dioxide between an organism and the environment. In air-breathing vertebrates like human beings, respiration takes place in the respiratory organs called lungs.  Nervous System: The network of nerve cells and fibers which transmits nerve impulses between parts of the body. It consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS contains the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons that connect the CNS to every other part of the body. 8
  9. 9. System Highlights:  Skeletal System: The skeletal system includes all of the bones and joints in the body. Each bone is a complex living organ that is made up of many cells, protein fibers, and minerals. The skeleton acts as a scaffold by providing support and protection for the soft tissues that make up the rest of the body. The skeletal system also provides attachment points for muscles to allow movements at the joints.  Muscular System: The muscular system is an organ system consisting of skeletal, smooth and cardiac muscles. It permits movement of the body, maintains posture, and circulates blood throughout the body. The muscular system in vertebrates is controlled through the nervous system, although some muscles (such as the cardiac muscle) can be completely autonomous. Together with the skeletal system it forms the musculoskeletal system, which is responsible for movement of the human body.  Digestive System: The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body. Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract). The alimentary canal is made up of the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines. 9
  10. 10. System Highlights:  Endocrine System: The endocrine system includes all of the glands of the body and the hormones produced by those glands. The glands are controlled directly by stimulation from the nervous system as well as by chemical receptors in the blood and hormones produced by other glands. By regulating the functions of organs in the body, these glands help to maintain the body’s homeostasis.  Exocrine System: The exocrine system is an organ system consisting of the skin, hair, nails, and exocrine glands. The skin is only a few millimeters thick yet is by far the largest organ in the body. The average person’s skin weighs 10 pounds and has a surface area of almost 20 square feet. Skin forms the body’s outer covering and forms a barrier to protect the body from chemicals, disease, UV light, and physical damage.  Lymphatic System: The immune and lymphatic systems are two closely related organ systems that share several organs and physiological functions. The immune system is our body’s defense system against infectious pathogenic viruses, bacteria, and fungi as well as parasitic animals and protists. The immune system works to keep these harmful agents out of the body and attacks those that manage to enter. 10
  11. 11. System Highlights:  Urinary System: The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter the blood to remove wastes and produce urine. The ureters, urinary bladder, and urethra together form the urinary tract, which acts as a plumbing system to drain urine from the kidneys, store it, and then release it during urination. Besides filtering and eliminating wastes from the body, the urinary system also maintains the homeostasis of water, ions, pH, blood pressure, calcium and red blood cells.  Reproductive System: The male reproductive system includes the scrotum, testes, spermatic ducts, sex glands, and penis. These organs work together to produce sperm, the male gamete, and the other components of semen. These organs also work together to deliver semen out of the body and into the vagina where it can fertilize egg cells to produce offspring. The female reproductive system includes the ovaries, fallopian tubes, uterus, vagina, vulva, mammary glands and breasts. These organs are involved in the production and transportation of gametes and the production of sex hormones. The female reproductive system also facilitates the fertilization of ova by sperm and supports the development of offspring during pregnancy and infancy. 11
  12. 12. Classification of Biomedical Instruments:  All biomedical instruments are categorized into different sectors of operations. Following shows different instruments those are employed in different functional areas. 12 BLOOD INSTRUMENTS HEART INSTRUMENT Blood Pressure meter ECG Blood PH meter Pace Maker Blood flow meter Defibrillator Blood cell counter Heart Lung Machine Calorimeter Bed side Monitor Spectra – Photometer Plethysmograph Flame photometer Electronic stethoscope Digital BP meter Phonocardiograph
  13. 13. Classification of Biomedical Instruments: BRAIN INSTRUMENTS MUSCLE INSTRUMENTS EEG EMG Tomograph Muscle Stimulator 13 KIDNEY INSTRUMENTS EAR INSTRUMENTS Dialysis Instrument Audiometer Lithotripsy Hearing aid EYE INSTRUMENTS LUNG INSTRUMENTS Occulometer Spirometer Aid for blind
  14. 14. Classification of Biomedical Instruments: BODY INSTRUMENTS PHYSIOTHERAPHY INSTRUMENTS Ultrasonography Diathermy, Short Wave Thermograph Electro Sleeper Radiograph Vibrator (Massage type) EPF U.V. Lamph Endoscope Microwave Diathermy 14
  15. 15. Biomedical Measurements  Biomedical instrumental measurements are divided in to two categories. 1. IN VIVO MEASURMENTS – In vivo measurements are made on or within the living organism itself, e.g. a device inserted into the blood stream to measure the pH of the blood directly. 2. IN VITRO MEASURMENTS – In vitro measurements are made outside the body, even though it relates to the functions of the body, e.g. measurements of pH of sample of blood that has been drawn from patients’ body. 15
  16. 16. Sources of Biomedical Signals:  Biometrics is the branch of science that deals with the measurement of physiological variables and parameters.  Biomedical signals are used primarily for extracting information on biological system under investigation. 1. Bioelectric Signals: These are unique to the biomedical systems. They are generated by nerve cells and muscle cells. Their 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 cell constitutes the bio-electric signal. The most common examples of bioelectric signals are the ECG (electrocardiographic) and EEG (electroencephalographic) signals. 2. Bio acoustic Signals: The measurement of acoustic signals created by many biomedical phenomena provides information about the underlying phenomena. The examples of such signals are; 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. 3. Biomechanical Signals: These signals originate from some mechanical function of the biological system. They include all types of motion and displacement signals, pressure and flow signals. The movement of the chest wall in accordance with the respiratory activity is an example of this type of signal. 16
  17. 17. Sources of Biomedical Signals: 4. Biochemical Signals: The signals which are obtained as a result of chemical measurements from the living tissues or from samples analyzed in the laboratory. The examples are measurement of partial pressure of carbon dioxide (pCO2), partial pressure of oxygen (pO2) and concentration of various ions in the blood. 5. Bio magnetic Signals: Extremely weak magnetic fields are produced by various organs such as the brain, heart and lungs. The measurement of these signals provides information which is not available in other types of bio signals such bioelectric signals. A typical example is that of magneto encephalograph MEG signals from the brain. 6. Bio – optic Signals: These signals are generated as result of optical functions of the biological systems, occurring either naturally or induced by the measurement process. For example, blood oxygenation may be estimated by measuring the transmitted/back scattered light from a tissue at different wavelengths. 7. Bio – impedance Signals: The impedance of the tissue is a source of important information concerning its composition, blood distribution and volume. The measurement of galvanic skin resistance GSR is a typical example of this type of signal. The bio-impedance signal is also obtained by injecting sinusoidal current in the tissue and measuring the voltage drop generated by the tissue impedance. The measurement of respiration rate based on bio-impedance technique is an example of this type of signals. 17
  18. 18. Sources of Biomedical Signals 18 Fig 1: Sources of Biomedical Signals
  19. 19. Man - Instrumentation System:  The overall system including both the human body and the instrumentation required for its measurement is called the man – instrumentation system. The set of instruments and equipment utilized in the measurement of multiple characteristics plus the presentation of these information in a readable and interpretable manner is called an instrumentation system. In the man – instrumentation system, the human body is treated as the black box (the unknown system) within which several kinds of signals and systems are found, all interacting with each other. 19
  20. 20. Man - Instrumentation System:  Components of the Man – Instrumentation system: 1. The system components of Man – Instrumentation system are listed below. 2. The subject - The human being on which the measurements are to be carried out is referred to as the subject under study or monitoring. 3. Stimulus: in many cases, an external triggering is required to initiate the measurement process. This stimulus may be visual, auditory, tactile or direct electrical stimulation of some part of the nervous system. This forms of the major components of the man – instrumentation system. 4. Transducer: This is a device capable to converting the measured signal into a form of energy interpretable and recording for further study and analysis. 20
  21. 21. Man - Instrumentation System: 5. Signal conditioning equipment: Most signals those are received from human body are very light signals. Therefore these signals need amplification, modification so that they can be interpreted properly. 6. Display Equipment: To be meaningful, the electrical output of the previous component must be converted into a form that can be perceived by human senses. This requirement makes the display equipment one of the vital components in man – instrumentation system. 7. Recording, Data – processing and Transmission Equipment: for later and further analysis of the measured variables, the data needs to be recorded and transmitted over locations making this module a very vital composition of the system. 8. Control Device: this forms the final component of the system giving the operators the flexibility of automatic control of the stimulus. This is achieved by incorporating a feedback loop in the system. 21
  22. 22. Man - Instrumentation System: 22 Fig 2: Man – Instrument System Fig 3: Basic Medical Instrumentation System
  23. 23. Common Medical Measurands:  The following table shows few of the measurement parameters generally used in medical instrumentation system along with its operational range and methods employed in attaining the same. TABLE I: Measurement Parameters with range 23 Measurement Type Range Frequency Hz Method Blood Flow 1 to 300 mL/s 0 to 20 EM or US Blood Pressure 0 to 400 mm Hg 0 to 50 Cuff or Strain Gage Cardiac Output 4 to 25 L/min 0 to 20 Fick, dye dilution ECG 0.5 to 4 mV 0.05 to 150 Skin Electrodes EEG 5 to 300 μV 0.5 to 150 Scalp Electrodes EMG 0.1 to 5 mV 0 to 10000 Needle Electrodes Electroretinography 0 to 900 μV 0 to 50 Contact Lens Electrodes pH 3 to 13 pH units 0 to 1 pH Electrodes pCO2 40 to 100 mm Hg 0 to 2 pCO2 Electrodes pO2 30 to 100 mm Hg 0 to 2 PO2 Electrodes Pneumotachography 0 to 600 L/min 0 to 40 Pneumatochometer Respiratory Rate 2 to 50 breaths/min 0.1 to 10 Impedance Body Temperature 32 °C to 40 °C 0 to 0.1 Thermistor
  24. 24. Recording Instruments  Following are the set of few instruments that found application as a recording instrument. 1. Electrocardiography 2. Electromyography 3. Electro encephalography 4. Expirography 5. Phonocardiography 6. Plethysmography 7. Thermography 8. Tomography 9. Ultrasonography 10. Radio graph (X-ray) 24
  25. 25. Constraints in Medical Instrument Designs:  The signal to be measured inflicts limitations on how it should be acquired and administered. Also the frequency range or signal strength is much lower than conventional measuring parameters. .  Interference and cross talk between different organs and systems of the body may bring down the accuracy and therefore diagnosis of the problem.  Placement of sensors is one major challenge in the scope of biomedical instruments as perfect and most appropriate position is of primordial importance but it varies from person to person.  Safety is the biggest concern in this field. The process of measurement must not endanger the person on whom measurements are being made.  Operators’ expertise and constraints is a challenging aspect in this field.  Measurement variability is inherent at molecular, organ and body level. It is often impossible to hold one variable constant while measuring the relationship between two others. 25
  26. 26. References:  Introduction To Biomedical Equipment Technology; J. J. Carr, John Michael Brown  Basic Concepts of Medical Instrumentation: Application and Design; John G. Webster  Biomedical Instrumentation And Measurements; Leslie, Cromwell.  Biomedical Instrumentation; R. S Khandpur and Raghbir Khandpur.  Introduction to Biomedical Instrumentation; Barbara Christe.  Biomedical Instrumentation; Dr. M Arumugam.  Introduction To Biomedical Instrumentation; Mandeep Singh  Principles of Medical Electronics and Biomedical Instrumentation; C. Raja Rao, Sujoy K. Guha    26