Bioinstrumentation. Kuo-Sheng Cheng, Ph.D. Department of Biomedical Engineering National Cheng Kung University

Transcription

1 Bioinstrumentation Medical Instrumentation: Application and Design Third Edition John G. Webster, Editor Kuo-Sheng Cheng, Ph.D. Department of Biomedical Engineering National Cheng Kung University

2 The Importance of Medical Instrumentation Diagnosis and therapy depend heavily on the use of medical instrumentation. Medical procedures: Medicine can be defined as a multistep procedure on an individual by a physician, group of physician, or an institute, repeated until the symptoms disappear.

3 The Importance of Medical Medical procedure Instrumentation 1) Collection of data - qualitative and/or quantitative 2) Analysis of data 3) Decision making 4) Treatment planning based on the decision 5) Repeat

4 A Story of New Medical Device The invention, prototype design, product development, clinical testing, regulatory approval, manufacturing, marketing, and sale of a new medical instrument add up a complex, expensive, and lengthy process. A success story - Technicon s Auto Analyzer

5 Development of Technicon s Auto Analyzer The inventor - Leonard Skeggs, Chair of Department of Pathology at Case Western Reserve University - Dr. Alan Moritz Technicon Corporation founders - Edwin C. Whitehead, and his father a four-page confidential disclosure form

6 Development of Technicon s Auto Analyzer Two key persons to recall the invention - Technicon s only salesman, Ray Roesch, and the doctor at the Cleveland Veterans Adminstration Hospital, Joseph Kahn. Patent application and protection Marketing strategy

7 Development of Technicon s Auto Analyzer Factors affected the success it allows an enormous improvement in quality of laboratory test results, and an enormous reduction in the cost of doing chemical analysis. accurate laboratory data are useful in diagnosis. reimbursement policies increase the availability of health care.

8 Evolutionary product v.s. Revolutionary product Generalized medical instrumentation system measurand sensor signal conditioning output display auxiliary elements

9 Control And feedback Sensor Power source Measurand Primary Sensing element Variable Conversion element Signal processing Output display Perceptible output Calibration signal Data storage Data transmission Radiation, electric current, or other applied energy Figure 1.1 Generalized instrumentation

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12 Alternative Operational Modes Direct-Indirect modes Sampling and Continuous modes Generating and Modulating sensors Analog and Digital Modes Real-time and Delayed-time Modes

13 Medical Measurement Constraints Many crucial variables in living systems are inaccessible. Variables measured are seldom deterministic. Nearly all biomedical measurements depend on the energy. Operation of instruments in the medical environment imposes important additional constraints.

14 Classifications of Biomedical Instruments The sensed quantity The principle of transduction The organ system for measurement The clinical medicine specialities

15 Classifications of Biomedical Instruments Based on the activities involved in the medical care, medical instrumentation may be divided into three categories: diagnostic devices therapeutic devices monitoring devices

16 Generalized Static Characteristics Accuracy Precision Resolution Reproducibility Statistical control Static sensitivity, Sensitivity drift Zero drift Linearity

17 Characteristic with zero and sensitivity drift y (Output) Total error due to drift y (Output) D y' + Sensitivity drift D x' d - Zero drift Intercept b Dx d Dy Slope m = Dy Dx d + Zero drift - Sensitivity drift y = mx d + b x d (Input) x d (Input) (a) (b) Figure 1.3 (a) Static-sensitivity curve that relates desired input x d to output y. Static sensitivity may be constant for only a limited range of inputs. (b) Static sensitivity: zero drift and sensitivity drift. Dotted lines indicate that zero drift and sensitivity drift can be negative.

18 Generalized Static Characteristics Input ranges Input impedance

19 Generalized Dynamic Characteristics Differential or Integral equations Transfer functions Time delay

20 Figure 1.8 Design process for medical instruments Choice and design of instruments are affected by signal factors, and also by environmental, medical, and economic factors.

21 Regulation of Medical Devices Medical Device Amendments to the Federal Food, Drug, and Cosmetics Act Safe Medical Devices Act Medical Device: any item promoted for a medical purpose that does not rely on chemical action to achieve its intended effect

22 Regulation of Medical Devices Medical devices were classified in two ways: Class I (general controls), Class II (performance standards), and Class III (premarketing approval) Preamendment, Postamendment, Substantially equivalent, implant, custom, investigation, and transitional.

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25 Biomedical Transducer Measuring is the key to understand, and transducer plays an important role in measurement. Kuo-Sheng Cheng, Ph.D. Institute of Biomedical Engineering National Cheng Kung University

26 What is the Transducers? In principle, Transducers are devices that convert signals in one form of energy into signals in another form of energy. Sensors Actuator Conventional v.s. Intelligent Transducers

27 What are the Transduers, Sensors, and Actuators? Transducer - A device that converts energy of one form to another. Sensor - A device that converts a physical parameter to an electric output. Actuator - A device that converts an electric signal to a physical output.

28 Conventional v.s. Intelligent Transducer Conventional transducer Physical or Chemical Parameters Sensor Transmission Link Signal Processing Display Storage Actuator... Further Processing

29 Conventional v.s. Intelligent Intelligent transducer Transducer Physical or Chemical Parameters Sensing Element & Signal Processing Transmission Link Signal Processing Display Storage Actuator... Further Processing

30 Transducer Categories By application By physical or chemical principles used By the process used to convert the signal energy into an electrical signal

31 Three types of output signal Self-generating (active) transducers: The electrical signal output of transducer is generated from another form of input energy. e.g. Light in ~ I R L Electrical Signal Output Photovoltaic cell

32 Three types of output signal Modulating (passive) transducer: The input signal energy of transducer is used to modulate the electrical energy flow from the power supply to the transducer output. e.g. Light in I R L Electrical Signal Output Photoconductive cell

33 Three types of output signal Tandem transducers: e.g. Light in The original input signal energy is converted to a final output of electrical energy through two or three effects or conversions in tandem. Modulated light Y-position Photoconductive cell I R L Electrical Signal Output

34 1. Sensor characteristics 2. Physical Sensors Displacement measurements Resistive Capacitive Inductive Piezoelectric Temperature measurements Optical measurements 3. Chemical Sensors Biochemical

35 Electronic Sphygmomanometer The System Design & Analysis Student: Cheng-Yu Chen Advisor: Kuo-Sheng Cheng Biomedical Imaging & Instrumentation Lab

36 Introduction The blood pressure measurement -Invasive method Stephen Hales placed a glass tube in the artery of horse for blood pressure measurement in The measurement of blood pressure with a mercury sphygmomanometer was first invented by J. M. Poiseuille in Noninvasive method Limb-occluding device that contained an arm cuff was first invented by S. Riva-Rocci in L. Hill and H. Barnard published a modified sphygmomanometer with cuff in N. S. Korotkov invented an auscultatory measurement of systolic and diastolic blood pressure in 1905.

37 Introduction (cont.) Stephen Hales demonstrated the blood pressure in horse in 1733.

38 Introduction (cont.) Riva-Rocci s sphygmomanometer, 1896 Blood pressure measurement using Korotkov s method, 1905 *E. O Brien and D. Fitzgerald, The history of indirect blood pressure measurement, Handbook of Hypertension, Vol. 14: Blood Pressure Measurement

39 Korotkov s method Introduction (cont.)

40 Introduction (cont.) The oscillometric method

41 System Description RS-232 Data transmission Display unit Analog signal processing Circuits Microprocessor with A/D converter Pressure Signal Low-Pass Filter High-Pass Filter Instrumentation Amplifier Air pump & valve control circuit Cuff Pressure Sensor

42 The system circuits Hardware Design Display Unit Microprocessor With A/D Converter Pressure Sensor Analog Signal Processing Circuit RS-232 Data Transmission Air Pump & Valve Control Circuit