HEMN 213 Lecture-1: Introduction PDF

Lecture-1: Introduction Sherif H. El-Gohary , Phd Assistant Professor,Biomedical Engineering Biomedical Transducer [email protected] HEMN213 Syllabus and Goal of the Course Syllabus: Basic concepts of Biomedical sensors. Goal o...

Lecture-1: Introduction Sherif H. El-Gohary , Phd Assistant Professor,Biomedical Engineering Biomedical Transducer [email protected] HEMN213 Syllabus and Goal of the Course Syllabus: Basic concepts of Biomedical sensors. Goal of the Course: This course is designed to introduce the instrumentation and measurement concepts and to illustrate their implementations in the biomedical field with examples. Eventually, it will develop the ability of biomedical engineering students to identify components of a biomedical sensors, from the human body to the display, and analyze principles and problems related to each section. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Course Learning Objectives After completing this course, students should be able to: Identify sensors and the critical issues for sensor choice, placement, and circuit implementation Measure signals in medical environment and evaluate the quality of effect of measuring instruments on the measured data. Design circuits including sensors as 1st prototype for different medical devices. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Textbook and References Textbook: Webster, J. G. (ed); "Measurement Instrument ation Sensors," 2nd ed. CRC, 1999; References: 1. Enderle J.D. and Bronzino J.D. Introduction to Biomedic al Engineering, 3rd ed. Academic Press; 2011; 2. Carr, J.J. and Brown J.M.; "Introduction to Biomedical Eq uipment Technology," Prentice-Hall, 4th ed. 2001; Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 Types of sensors which will be include Bio-potential Electrodes Mechanical Transducers Temperature Transducers Light measurements Measurement of Liquid and Gas Flows Pressure, Motion, and Force Measurement Etc…. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Assessments Weights Assessment type Number Contribution Attendance & Participation Lectures 5 Presentations 2-3 5-10 Lab projects (Practical (preliminary work, lab 4-5 20 work and report)) Project 1 5-10 Midterm Exam 1 20 Final exam 1 40 Total 100 Bonuses Tutorial attendance Design of creative experiments Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Biomedical Engineering Metaphorical bridge Medicine Engineering Rehearsal: Engineers help in developing medicine and medical technology contributes to furthering the engineering in many fronts. Give Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 two examples for each one of them. X-ray (roentgen) in 1895 ECG in 1903 EEG in 1929 1st implantable pacemaker 1st CAD machine, In 1961 1st microprocesso r in 1972 Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 IBM PC in 1981 Introduction to Biomedical Sensors Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Questions to Answer for Measurement Why measure? What to measure? How to measure? How to establish conditions for measurement? How to verify the data? How to convert data into information? How to present the results? How to interpret the results? Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Realization of the Greatness of A Scientific Action Later scientists measured the "acceleration" of earths gravity. That lead to understanding how FORCE, acceleration and mass relate. That lead us to understand how the universe works and how to get to the MOON! Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 You Can't Manage What You can't manage what you don't measure. You Don't Measure An old management adage that is accurate today. Unless you measure something you don't know if it is getting better or worse. You can't manage for improvement if you don't measure to see what is getting better and what isn't. Peter Drucker Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  What is a Biomedical Sensor? Any instrumentation system can be described as having three fundamental components:  a sensor,  a signal processor,  and a display and/or storage device. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  What is a Biomedical Sensor? Although all these components of the instrumentation system are important, the sensor serves a special function in that it interfaces the instrument with the system being measured. In the case of biomedical instrumentation, a biomedical sensor is the interface between the electronic instrument and the biological system. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 Generic scheme of a measurement Environment Disturbance Influence x +D x y +Dy1 Measurement Measurement Matching Matching Observer Object System (noisy) Influence Influence “What is not measured does not exist.” Max Born, 1926 Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Definitions Transducer: a device that converts one form of energy into another. Sensor: a device that converts a physical parameter to an electrical output. Actuator: a device that converts an electrical signal to a physical Sherif El-Gohary, Ph.D. output. Biomedical Transducer HEMN213  CLASSIFICATION OF TRANSDUCERS Active & Passive Transducers Absolute & Relative Transducers Direct & Complex Transducers Analog & Digital Transducers On the basis of principle used Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Active vs. Passive Transducers: Active Transducers:  Add energy to the measurement environment as part of the measurement process.  Requires external power supply. Strain gauge, potentiometer & etc. Passive Transducers :  Do not add energy as part of the measurement process but may remove energy in their operation.  Does not require external power supply Thermocouple, photo-voltaic cell & etc. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Absolute & Relative Transducers  An absolute Transducers detects a stimulus in reference to an absolute physical scale that is independent on the measurement conditions.  Thermistor: Its electrical resistance directly relates to the absolute temperature scale of Kelvin.  Relative Transducers produces a signal that relates to some special case.  Thermocouple: It produces an electric voltage that is function of a temperature gradient across the thermocouple wires. Thus, a thermocouple output signal cannot be related to any particular temperature without referencing to a known baseline. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  DIRECT & COMPLEX TYPE Direct transducer converts a stimulus into an electrical signal or modifies an electrical signal by using an appropriate physical effect. Complex transducer in addition needs more than one transducers or may have computing machines. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 Analog and digital signals Amplitude Amplitude Time Time Analog signals can have any amplitude Digital signals have a limited number value of amplitude values Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 Continuous and discrete-time signals Amplitude Amplitude Time Time Continuous signals have values at every instant of time Discrete-time signals are sampled periodically and do not provide values between these sampling times Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 Example to sampled data Complete blood count for a male subject. Laboratory test Typical value Hemoglobin 13.5 to 18 g/dL Hematocrit 40 to 54% Erythrocyte count 4.6 to 6.2  106/ L Leukocyte count 4500 to 11000/ L Neutrophil 35 to 71% Band 0 to 6% Lymphocyte 1 to 10% Differential count Monocyte 1 to 10% Eosinophil 0 to 4% Basophil 0 to 2%  Measurand Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 A simplified measurement system Outputs Signal Signal Data Sensor Measurand conditioning processing displays Feedback Data Data Effector storage communication A typical measurement system uses sensors to measure the variable, has signal processing and display, and may provide feedback. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Measurement with or without a clinician (a) (b) Patient Instrument Patient Clinician Instrument (a) Without the clinician, the patient may be operating in an ineffective closed loop system. (b) The clinician provides knowledge to provide an effective closed loop system. Reporting abnormalities Abnormal Clinician readings Patient Instrument In some situations, a patient may monitor vital signs and notify a clinician if abnormalities occur. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 Medically important measurands  Biopotentials  Pressure  Flow  Dimensions (imaging)  Displacement (velocity, acceleration and force)  Impedance  Temperature  Chemical concentrations Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 Origins of common biological signal Name of organ in Latin Type of Type of presenting signal prefix+ name + suffix Electro Cardio Gram Mechano Encepha Graph Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 Pnemo Myo Graphy Voltage and freq. ranges of some common biopotential signals Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Setting sensor specifications Specification Value Pressure range –30 to +300 mmHg Overpressure without damage –400 to +4000 mmHg Maximum unbalance ±75 mmHg Linearity and hysteresis ± 2% of reading or ± 1 mmHg Risk current at 120 V 10 A Defibrillator withstand 360 J into 50  Sensor specifications for a blood pressure sensor are determined by a committee composed of individuals from academia, industry, hospitals, and government. Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Specifications for ECG Specification Value Input signal dynamic range ±5 mV Dc offset voltage ±300 mV Slew rate 320 mV/s Frequency response 0.05 to 150 Hz Input impedance at 10 Hz 2.5 M Dc lead current 0.1 A Return time after lead switch 1s Overload voltage without damage 5000 V Risk current at 120 V 10 A Specification values for an electrocardiograph are agreed upon by a committee  Engineering Design  Design is the innovative process of identifying needs and then devising a product to fill those needs.  It is a problem solving using the existing knowledge and technology: integration of knowledge.  It considers alternative solutions for selecting the optimal solution with a fixed goal or specifications in mind.  Design criteria Initial instrument design Signal factors Prototype tests Environmental factors Final instrument Measurand design Medical factors FDA, BMD approval Economical Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 factors Production  Signal factors  Sensitivity  Range  Differential or absolute input  Input impedance  Transient and frequency response  Accuracy  Reliability Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Environmental factors  Specificity  Signal-to-noise ratio  Stability  Temperature  Humidity  Pressure  Acceleration  Shock  Vibration  Radiation  Power requirements Sherif El-Gohary, Ph.D.  Mounting size, shape Biomedical Transducer HEMN213  Medical factors  Invasive or non-invasive  Tissue-transducer interface requirements  Material toxicity  Electrical safety  Radiation and heat dissipation  Patient discomfort Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Economic factors  Cost  Availability  Warranty  Consumable requirements  Compatibility with existing equipment Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Sensors : taxonomies  Measurand  Usage type physical sensor multiple-use(continuous monitoring) sensor chemical sensor disposable sensor biological sensor(cf : biosensor)  Invasiveness  Power requirement invasive(contact) sensor passive sensor noninvasive(noncontact) sensor active sensor Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213  Sherif El-Gohary, Ph.D. Biomedical Transducer HEMN213 Thank you Please Are still magic words