Biomedical Sensors and Instruments

Citation

Togawa, T., Tamura, T., & Öberg, P. Å. (2011). Biomedical Sensors and Instruments (2nd ed.). CRC Press.

Chapter Summary

The book is organised by the physical or chemical quantity being measured rather than by device. Its seven chapters begin with general measurement concepts and then take pressure, flow, motion and force, temperature and heat, bioelectric and biomagnetic signals, and chemical quantities in turn. The publisher describes it as an introduction running from underlying principles to practical applications, and the second edition is about 420 pages with some 340 illustrations. Most chapters open with a section on the quantities or objects to be measured before turning to sensors, and each ends with a list of references.

Chapter 1: Fundamental Concepts

The opening chapter covers signals and noise in the measurement, the characteristics of the measurement system, the determination of absolute quantity and the units of measurement quantities. It is the common vocabulary for the sensor chapters that follow.

Chapter 2: Pressure Measurements

After a section on the quantities involved, the chapter separates direct pressure measurement from indirect pressure measurement.

Chapter 3: Flow Measurement

Flow is handled in three settings: blood flow in single vessels, tissue blood flow and respiratory gas flow, after a section on the quantities involved.

Chapter 4: Motion and Force Measurement

Covers the objects of measurement, then motion measurements and force measurements.

Chapter 5: Temperature, Heat Flow, and Evaporation Measurements

The chapter treats temperature sensors, noncontact temperature measurement techniques, clinical thermometers, heat flow measurements and evaporation measurement.

Chapter 6: Bioelectric and Biomagnetic Measurements

After the objects of measurement, the chapter covers electrode theory, then surface potential electrodes, micro and suction electrodes, and biomagnetism.

Chapter 7: Chemical Measurement

Covers the objects of chemical measurement, chemical sensors and the continuous measurement of chemical quantities.

Key Concepts

Chapter 1: Fundamental Concepts

• Signals and noise in measurement: the book begins with the signal and the noise that accompanies it in any measurement, before turning to specific sensors.
• Measurement system characteristics: the properties of the system through which a quantity is sensed.
• Absolute quantity and units: how a measured value is tied to a defined unit.

Chapters 2–4: Mechanical Quantities

• Direct and indirect pressure measurement: two routes to a pressure value.
• Flow in vessels, tissue and airways: blood flow in single vessels, tissue blood flow and respiratory gas flow as distinct problems.
• Motion and force: the sensing of movement and of applied force.

Chapters 5–7: Thermal, Electrical and Chemical Quantities

• Temperature, heat flow and evaporation: contact and noncontact temperature methods, and the measurement of heat and water loss.
• Electrodes: electrode theory and the surface, micro and suction electrodes used to pick up biopotentials.
• Biomagnetism: measurement of magnetic fields produced by the body.
• Chemical sensors: sensors for continuous measurement of chemical quantities.

Critical Analysis

Strengths

• Organised by quantity. Each chapter takes a physiological quantity (pressure, flow, motion, temperature, bioelectricity, chemistry) and presents the sensing methods for it, which suits a reader who starts from a measurement problem and wants to compare methods.
• A principles-to-practice approach. The publisher describes the book as an easy-to-understand introduction to the various kinds of biomedical sensors, from underlying principles to practical applications.
• Wide sensing range. The contents cover pressure, flow, motion, temperature, heat flow, evaporation, biopotential, biomagnetism and chemical quantities in one volume, with specific entries such as noncontact thermometry and tissue blood flow.
• Common frame. The first chapter on signals, noise and system characteristics gives every later chapter the same measurement vocabulary.

Limitations

• Sensors, not instruments as systems. The chapters stop at sensing and measurement; the contents list shows no chapters on amplifiers, data acquisition or the design of complete monitoring systems, which a reader will need to find in an instrumentation textbook.
• Dated edition. The second edition dates from 2011, so newer sensor technologies are outside it.
• No chapters on imaging or signal analysis. The scope is limited to the seven quantities listed; interpretation of the recorded signals is a separate subject.

Where It Fits in the Course

Within the medical instrumentation course, this book is the sensor reference. Introduction to Biomedical Instrumentation: The Technology of Patient Care by Barbara Christe is an accessible introduction to the equipment in hospitals, and Principles of Biomedical Instrumentation by Andrew Webb is a textbook in the Cambridge Texts in Biomedical Engineering series. Medical Instrumentation: Application and Design, edited by John Webster and Amit Nimunkar, is the standard engineering textbook on how medical measurement devices work and is a natural main text. Northrop's Analog Electronic Circuits for Biomedical Instrumentation is a graduate-level text on the analog electronics that condition biomedical signals, and the course list also holds a book on transducers for biomedical measurements.

Togawa, Tamura and Öberg complements these: it is the text to pick up after a general instrumentation course when the question is what a given sensor measures and how, and it pairs with Northrop's circuits book on the electronics side.

How to Use This Book

The book suits upper-level undergraduates and graduate students in biomedical engineering, engineers developing physiological monitors and clinical scientists who want to understand what a sensor reports. Familiarity with basic physics, electronics and physiology helps.

A practical plan:

• Start with Chapter 1, whatever the quantity of interest, for the treatment of signals, noise and measurement systems.
• Choose by quantity: Chapters 2 and 3 for cardiovascular and respiratory work, Chapter 4 for movement and biomechanics, Chapter 5 for thermometry and heat exchange, Chapter 6 for biopotential recording and biomagnetism, Chapter 7 for chemical sensing.
• Use the references at the end of each chapter as a route to the original sensor literature.
• Compare methods: for each quantity, tabulate the sensing principles the chapter describes and note what each requires of the body and of the measurement system.

Pair the book with a general instrumentation textbook for amplifier, data-acquisition and system-level topics.