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Medical Imaging &
Instrumentation Laboratory
BME, NCKU
BioinstrumentationMedical Instrumentation: Application and Design Third Edition
John G. Webster, Editor
Kuo-Sheng Cheng, Ph.D.
Department of Biomedical Engineering
National Cheng Kung University
Medical Imaging &
Instrumentation Laboratory
BME, NCKU
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.
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The Importance of Medical
Instrumentation
• Medical procedure
– 1) Collection of data - qualitative and/or
quantitative
– 2) Analysis of data
– 3) Decision making
– 4) Treatment planning based on the decision
– 5) Repeat
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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
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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
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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
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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.
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• Evolutionary product v.s. Revolutionary
product
• Generalized medical instrumentation system
– measurand
– sensor
– signal conditioning
– output display
– auxiliary elements
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Figure 1.1 Generalized instrumentation
Perceptible
outputOutput
display
Control
And
feedback
Signal
processing
Data
transmissionData
storage
Variable
Conversion
element
Sensor
Primary
Sensing
element
Measurand
Calibration
signal
Radiation,
electric current,
or other applied
energy
Power
source
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Medical Imaging &
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BME, NCKU
Medical Imaging &
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Alternative Operational Modes
• Direct-Indirect modes
• Sampling and Continuous modes
• Generating and Modulating sensors
• Analog and Digital Modes
• Real-time and Delayed-time Modes
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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.
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Classifications of Biomedical
Instruments
• The sensed quantity
• The principle of transduction
• The organ system for measurement
• The clinical medicine specialities
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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
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Generalized Static Characteristics
• Accuracy
• Precision
• Resolution
• Reproducibility
• Statistical control
• Static sensitivity, Sensitivity drift
• Zero drift
• Linearity
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Figure 1.3 (a) Static-sensitivity curve that relates desired input xd 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.
Intercept bDxd
Dy
D x'd
D y'
y (Output)
y = mxd + b
xd (Input)
(a)
Slope m =Dy
Dxd
Total error due to drift
Characteristic with zero and sensitivity drift
+ Zero
drift
+ Sensitivity
drift
- Sensitivity drift
- Zero drift
(b)
y (Output)
xd (Input)
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Generalized Static Characteristics
• Input ranges
• Input impedance
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Generalized Dynamic Characteristics
• Differential or Integral equations
• Transfer functions
• Time delay
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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.
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Instrumentation Laboratory
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Regulation of Medical Devices
• 1976 - Medical Device Amendments to the
Federal Food, Drug, and Cosmetics Act
• 1990 - 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
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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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Medical Imaging &
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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
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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
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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.
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Conventional v.s. Intelligent
Transducer
• Conventional transducer
SensorTransmission
Link
Signal
Processing
Display
Storage
Actuator
...
Further
Processing
Physical
or
Chemical
Parameters
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Sensing Element
&
Signal Processing
Transmission
Link
Conventional v.s. Intelligent
Transducer
• Intelligent transducer
Physical
or
Chemical
Parameters
Signal
Processing
Display
Storage
Actuator
...
Further
Processing
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Transducer Categories
• By application
• By physical or chemical principles used
• By the process used to convert the signal
energy into an electrical signal
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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 ~ RLI
Photovoltaic cell
Electrical
Signal
Output
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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 RLI
Photoconductive cell
Electrical
Signal
Output
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Three types of output signal
• Tandem transducers:
– The original input signal energy is converted to
a final output of electrical energy through two
or three effects or conversions in tandem.
e.g.Light in
Y-position
RLI
Photoconductive cellElectrical
Signal
OutputModulated
light
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1. Sensor characteristics
2. Physical Sensors
• Displacement measurements
• Resistive
• Capacitive
• Inductive
• Piezoelectric
• Temperature measurements
• Optical measurements
3. Chemical Sensors
• Biochemical
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Electronic Sphygmomanometer
Student: Cheng-Yu Chen
Advisor: Kuo-Sheng Cheng
Biomedical Imaging & Instrumentation Lab
The System Design & Analysis
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Introduction
• The blood pressure measurement
-Invasive methodStephen Hales placed a glass tube in the artery of horse for blood
pressure measurement in 1733.
The measurement of blood pressure with a mercury sphygmomanometer
was first invented by J. M. Poiseuille in 1828.
-Noninvasive methodLimb-occluding device that contained an arm cuff was first invented by
S. Riva-Rocci in 1896.
L. Hill and H. Barnard published a modified sphygmomanometer with
cuff in 1898.
N. S. Korotkov invented an auscultatory measurement of systolic and
diastolic blood pressure in 1905.
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Introduction (cont.)
• Stephen Hales demonstrated the
blood pressure in horse in 1733.
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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
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Introduction (cont.)
• Korotkov’s method
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Introduction (cont.)
• The oscillometric method
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System Description
Display unitRS-232 Data
transmission
Air pump & valve
control circuit
Microprocessor
with A/D converter
Cuff Pressure
Sensor
Instrumentation
Amplifier
High-Pass Filter
Low-Pass Filter
Analog signal
processing Circuits
Pressure
Signal
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Hardware Design
• The system circuits
Microprocessor
With A/D
Converter
Display Unit
RS-232 Data
Transmission
Air Pump & Valve
Control Circuit
Pressure
Sensor
Analog Signal
Processing Circuit