Medical Instrumentation (1)

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Medical Instrumentation (1)

• Mohamed Bingabr, Ph.D.Department of Engineering
  and Physics University of Central Oklahoma

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Outlines

• BME in medical instrumentation
• Common components of a measurement system
• System with feedback
• Biological system with feedback
• Medical devices with feedback

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BME Task

• Invent, design, build, and test devices for use
  in medicine.

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BME Task

• Oversee maintenance of medical instruments and
  adapting instruments to serve patients and doctors

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BME Task

• Do research and take measurements in research
  laboratories. (Third eye)

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Measurement Systems

• Sensor convert an input variable into measurable
  quantity
• Processor amplification, filtering, comparison,
  and other mathematical operations.
• Receiver presents readable results

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Systems With Feedback
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Feedback Blood Pressure
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Feedback Glucose Production
Normal blood glucose levels 80-90 mg/dL
by beta cells
by alpha cells
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Feedback ATP Production
ATP Adenosine Triphosphate ADP Adenosine
Diphosphate
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Feedback Muscle Reflex
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Systems With Feedback
Gain without feedback H
Case 1 without feedback G H 10 10
Case 2 with feedback H 100 10 F 0.09 G 10
??
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Systems Without Feedback
Example The system has a gain of 10 and due to
noise the gain may increase or decrease by 10.
In an ideal case the output will be 5 volt if the
input is 0.5 volt. Find the maximum and minimum
outputs if the system gain fluctuates by 10.
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Systems With Feedback
Example The system with the feedback has a gain
of 10. The forward gain H is 100 and the reverse
gain F is 0.09. Due to noise the forward gain H
may increase or decrease by 10. In an ideal case
the output will be 5 volt if the input is 0.5
volt. Find the maximum and minimum outputs if the
forward gain fluctuates by 10.
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Cardiac Pacemakers
Cardiac Pacemaker An electric device that
regulate the hearts beat by producing periodic
electric pulses to stimulate the hearts muscle.
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Cardiac Pacemakers
Timing Circuit pulse rate is 70 to 90 pulse per
minute Output Circuit Constant-Voltage Amplitude
pulses 5.0 to 5.5 V with duration of 0.5 to 0.6
msec.
What is the problem with fixed heart rate?
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Cardiac Pacemakers with Feedback
Physiological Variable SensorRight-ventricle
blood temperature ThermistorVenous blood oxygen
saturation Optical Oximeter Respiratory rate
and/or volume Thoracic electric- impedance

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Homework 3 (due April 13)

• Search for a biological system that uses feedback
  mechanism and write a paper describing the
  following points
• What does the feedback regulate.
• The mechanism and type of feedback (positive,
  negative, or both)
• What are the measured parameter (proteins, light,
  heat, pressure, etc..) to determine the states of
  the body.
• How does the feedback maintain the homeostasis of
  the body.
• What are the consequences of the absence of the
  feedback.
• Examples biological feedback
• Controlling the opening and closing of the iris
  in the Eye
• Controlling the stiffness of the outer hair cells
  in the cochlea of the ear
• Controlling the movement of the stapes in the
  middle ear.
• Production of white blood cells
• Production of proteins
• Muscles and movement