1

ELEC ENG 4BD4Lecture 1

Biomedical Instrumentation

Instructor: Dr. H. de Bruin

2

Cochlear Implant

3

Advances in Vision (Retinal Stimulation)

4

Mini Gastric Imaging

5

6

Calendar Description: Principles of instrumentation; Noise and interference in electrical measurements; Generation and nature of bioelectric potentials; electrodes and other transducers; electrical safety; neuromuscular and cardiovascular instrumentation; ultrasonics for bio-measurements other than imaging; computer interfaces for data acquisition systems. Course Objectives: Students will be able to apply the principles of electronic circuits and devices to the use and design of instrumentation in the biomedical area. They will have gained a basic knowledge of the operating principles of electrical and other transducers, analog and digital instrumentation, applied signal acquisition and processing, electrical safety in the medical environment, electrical properties of nerve and muscle physiology; and instrumentation used in cardiopulmonary, neurological, surgical, and rehabilitation areas of medicine.

7

Outline of Topics Lectures Topics •Measurement systems•Noise and coherent interference in measurements •Analog signal conditioning•Origin of Electrophysiological Signals •Measurement of Electrical potentials and Magnetic Fields from the Body surface•Electrodes; Half-Cell Potential; Equivalent Circuits •Biopotential amplifiers; Medical isolation amplifiers;

• Electrical Functioning of the heart• The ECG; Electrode placement;• The ECG; Vector cardiography; Driven-Leg ECG

amplifiers; Design Example: QRS complex segmentation

• Muscle • The EMG; Design Example: • Brain• The EEG; Design Example: Auditory event

related potentials• Other body surface potentials; EOG;

Electroretinogram Design Example: Human Computer Interface using EOG signals

8

1. Sensors commonly encountered in biomedical applications1. Temperature sensors – Design Example: ICU system

for body temperature monitoring2. Large displacement sensors

1. Motivation: Studying Muscle Activation and Fatigue during the propulsion of a wheel chair

2. LVDT3. Mechano-optical sensors4. Design Example: Studying Muscle Activation and

Fatigue during the propulsion of a wheel chair3. Small displacement sensors

1. Motivation: Respiratory gating for lung CT2. Strain gauges3. Piezoelectric transducers4. Design example: Respiratory gating for lung CT

4. Pressure measurements – 1. Invasive blood pressure measurements2. Automatic non – invasive blood pressure

measurements3. Design Example: Design a non-invasive blood

pressure measurement system5. Electro-chemical sensors – noninvasive blood gas

sensing with electrodes6. Optical sensors – Pulse Oximetry

9

1. Plethysmography; volume displacement; impedance

2. Ultrasound - Doppler US for blood and tissue velocity measurements

3. Stimulation of excitable tissues; Cardiac pacing and defibrillation

4. Digital Interfaces in measurement systems; Sampling Theorem; Quantization Noise; Dithering;

5. Digital to Analog converters; Analog to digital converters

10

Laboratory Sessions: Lab 1 : Differential amplifiers; DAQ / DSP / Statistical Analysis Key Concepts: Discrete Signals, Acquisition, Amplifiers, Frequency Domain Lab 2 : ECG / Heart RateKey Concepts: Biopotentials, Electrocardiogram, Einthoven's Triangle, Noise Artifact, Bio-instrumentation amplifier for ECGLab 3 : EEG Key Concepts: Alpha & Beta Waves (Alpha Blockers) – in phase or out of phase. Spectral and time analysis, Irregularities, Bio-instrumentation amplifier for EEGLab 4 : EMG & Motor Control Key Concepts: Muscle twitches, rectification, averaging, RMS, Force vs EMG, Filtering effects on applications of EMG, Bio-instrumentation amplifier for EMGLab 5 : EOG & Environmental Control Key Concepts: DC Signals, DC Amplifiers, Frequency component of blinking, Scaling of signals and creation of algorithms to make raw data into useful information, Bio-instrumentation amplifier for EOG

11

Textbooks (Optional): 1. Medical Instrumentation: Application and Design. John G. Webster2. Custom Courseware, Lecture Notes posted on the class websiteAdditional resources:1.Introduction to Instrumentation and Measurements; Second Edition; Robert B Northrop; Taylor and Francis; ISBN 0-8493-3773-92.Noninvasive Instrumentation and Measurement in Medical Diagnosis; Robert N. Northrop; CRC press; ISBN 0-8493-0961-13.Design and Development of Medical Electronic Instrumentation, D. Prutchi and M. Norri, Wiley-Interscience, 2005

12

Process of Measurement

• Understand the event (variable) you are measuring

• Is variable directly related to event?

• Is variable indirectly related to event?

• Is variable statistically related to event?

• Is event itself random?

13

Process of Measurement (cont’d)

• Is measurement biased (will final result have an offset, e.g. does it always read high)?

• What are unavoidable sources of noise?

• How much does this contaminate your measurement?

• Maximize your signal-to-noise ration SNR

14

Measurement Specifications

• What is amplitude range of selected variable

• What is bandwidth of variable (does variable change rapidly or slowly)?

• What is required resolution (smallest change you need to measure)?

• What is required accuracy?

15

Conditions of Measurement

• Biopotential signals are low amplitude (<1μv – 25 mv)

• Biopotential signals are low bandwidth (d.c. – 15 kHz)

• Body is volume conductor (specificity of signal source)

• Noise is high in bandwidth of biopotential signal (60 Hz: 30 mv on skin)

16

17

18