Biomedical Engineering
overview
Awada Ali Ph.D.
OUTLINES
• INTRODUCTION
• DEFINITION
• ACTIVITIES
• ROLE PLAYED BY BIOMEDICAL ENGINEER
• APPLICATIONS
INTRODUCTION
Many of the problems facing health care professionals are extremely
important to the engineer because they involve:
1. The fundamental aspects of device and systems analysis.
2. Design.
3. Practical application.
All of which lie at the heart of processes that are fundamental to
engineering practice. These medically relevant design problems can
range:
• From small and "simple" devices: Recording electrodes and
transducers used to monitor activity of specific physiological
processes in either a research or a clinical setting.
• To very complex large-scale constructs: Design and implementation
of automated clinical labs, and Hospital information systems.
DEFINITION
• Biomedical engineering is an interdisciplinary branch based
on both engineering and life sciences.
• Biomedical engineers apply electrical, chemical, optical,
mechanical, and other engineering principles to
understand, modify, or control biological systems.
• It ranges from theoretical, non-experimental undertakings
to state-of-the-art applications.
• It can includes research, development, implementation,
and operation.
BIOMEDICAL ENGINEERING ACTIVITIES
The field has moved significantly from being concerned
primarily with the development of medical devices to
includes many new career areas. These areas include:
• Detection, measurement, and monitoring of physiologic
signals.
• Diagnostic interpretation via signal-processing techniques
of bioelectric data.
• Therapeutic and rehabilitation procedures and devices.
• Devices for replacement of bodily functions (artificial
organs).
ROLE PLAYED BY BIOMEDICAL ENGINEER
Biomedical engineering involves training three types of
individuals:
1. Clinical engineer in health care
• The clinical engineer maintains the traditional service
relationship with the life scientists who originate a problem
that can be solved by applying the specific expertise of the
engineer.
• They must understand the biological situation to apply their
judgment and contribute their knowledge toward the solution
of the given problem as well as to defend their methods in
terms that the life scientist can understand.
2. Biomedical Design Engineer
• These individuals assume the gap between the technological
education of the physician and current technological capability.
• They examine some portion of the medical front and identify
areas in which advanced technology might be advantageous.
• They pose their own problem and then proceed to provide the
solution conceptually in the form of hardware or software.
• They must convince the medical community that they can
provide a useful tool.
• They should have a great deal of engineering and medical
knowledge as well as experience in numerous medical systems.
3. Research Scientist
• They are interested in applying engineering concepts and techniques to
the investigation and exploration of biological processes.
• The most powerful tool is the construction of an appropriate
mathematical model of the specific biological system under study.
• Through simulation techniques, they can use this model to understand
features that are too complex for analytical computation.
• The process of simulation facilitates the design of experiments that can
be performed on the actual biological system.
• This mathematical model can predict the effect of changes on a
biological system where actual experiments may be very difficult.
• The experiments results can be used to increase understanding of a
biological mechanism results from this iterative process.
CONCLUSIONS
Each of these roles envisioned for the biomedical engineer
requires a different attitude and a degree of knowledge about the
biological environment.
Rising social and economic expectations, and a need for the
development of more adequate techniques for:
• Prevention
• Diagnosis
• Treatment of disease
Development and employment of biomedical engineers have
become a necessity.
Introduction to
bioinstrumentation
Awada Ali Ph.D.
Introduction
• Bioinstrumentation
• Sensor or actuator (or both) used in medicine or biological research
• Usually directly connected to a living system
• Process, display or transmits biological data
• Areas of biomedical engineering that use these instruments
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•
•
•
•
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Bioelectronics (cardiac monitoring)
Biomechanics (tissue testing)
Biooptics (screening for biomarkers, radiation therapy)
Biomaterials (biocompatibility testing)
Biosystems (properties of cells)
Medical imaging (MRI, PET)
• Key to successful of biomedical engineering:
• Understand the physiology of a system
• Know the variables to be measured
• Know the function and limitations of the components
Generalized Medical Instrumentation System
Sensor
Signal conditioning
Medical and Physiological Parameters
BI Operational Modes
• Direct vs. Indirect
• Direct mode: measure desired measurand directly
•
if the sensor is invasive, direct contact with the measurand is possible
but expensive, risky and least acceptable
• Indirect mode: measure a quantity that is accessible and related to
the desired measurand
•
•
assumption: the relationship between the measurands is already known
often chosen when the measurand requires invasive procedures to
measure directly
• Example indirect mode
• Cardiac output (volume of blood pumped per minute by the heart)
• can be determined from measurement of respiration, blood gas
concentration & dye dilution
• Organ morphology can be determined from x-ray shadows
BI Operational Modes
• Sampling vs. Continuous mode
• Most sensors are analog, then signal is converted to digital for
processing or transmission
• Sampling: for slow varying measurands that are sensed infrequently like body
temperature & ion concentrations
• Continuous: for critical measurements requiring constant monitoring like
electro-cardiogram and respiratory gas flow
• Generating vs. Modulating
• Generating: also known as self-powered mode
•
•
derive their operational energy from the measurand itself
Example: piezoelectric sensors, solar cells
• Modulating: measurand modulates the electrical signal which is supplied
externally
•
modulation affects output of the sensor
• Example: photoconductive or piezoresistive sensor
BI Operational Modes
• Analog vs. digital modes
• most sensors are inherently analog (some optical sensors are exceptions)
• require analog-to-digital converters before any DSP techniques could
be applied for filtering
• Nyquist criterion: any continuous signal of frequency bandwidth f can
be fully reconstructed from its discrete time sample at sampling rate 2f
• Real-time vs. Delayed-time mode
• Real-time: real time processing is essential for bioinstrumentations
with feedback
• Example: ECG signals need to measured in real-time to determine an
impending cardiac arrest
• Delayed-time: some delay is acceptable for output
display/transmission systems
• Example: cell cultures which requires several days before any output is
acquired
Measurement Constraints
• The signal to be measured imposes constraints on how it
should be acquired and processed
• Signal/frequency ranges
• Most medical measurands parameters are typically much lower than
conventional sensing parameters (microvolts, mm Hg, low frequency)
• Interference and cross-talk
• Noise from environment, instruments, etc.
• Other measurands affect measurement (and can’t be isolated)
•
e.g., Cannot measure EEG without interference from EMG
Require filtering and/or compensation
Placement of sensor(s) in/on/near the body plays a key role in
any bio-instrumentation design
Measurement Constraints
• Measurement variability is inherent at molecular, organ and
body level Primary cause
• interaction between different physiological systems
• existence of numerous feedback loops whose properties are poorly
understood
• SAFETY
•
Due to interaction of sensor with living tissue, safety is a primary
consideration in all phases of the design & testing process
•
the damage caused could be irreversible
• In many cases, safe levels of energy is difficult to establish
• Safety of medical personnel also must be considered
• Operator constraints
• Reliable, easy to operate, rugged and durable
Classification of biomedical instruments
• Quantity being sensed
• pressure, flow or temperature
• makes comparison of different technologies easy
• Principle of transduction
• resistive, inductive, capacitive, ultrasonic or electrochemical
• makes development of new applications easy
• Organ systems
• cardiovascular, pulmonary, nervous, endocrine
• isolates all important measurements for specialists who need to know
about a specific area
• Clinical specialties
• pediatrics, obstetrics, cardiology or radiology
• easy for medical personnel interested in specialized equipment.
Instrument Characterization
• Enable comparison of available instruments
• Permit evaluation of new instrument designs
Generalized static characteristics
• Static characteristics:
• performance of instruments for dc or very low frequency inputs
• some sensors respond only to time-varying inputs and have no static
characteristics
• Dynamic characteristics:
• require temporal relationships to describe the quality of
measurements
Performance characteristics
Performance characteristics quantifying the quality of the
measurement or the signal processing
Static instrument characteristics:
• Accuracy: Difference between the true value and the measured value
normalized by the magnitude of the true value
• Several ways to express accuracy: most popular is in terms of
percentage of full-scale measurement
• Precision: Expresses number of distinguishable alternatives from which a
given result is selected
• High-precision does not mean high accuracy.
• Resolution: Smallest incremental quantity that can be measured with
certainty
• Reproducibility: Ability of an instrument to give the same output for equal
inputs applied over some period of time
Regulation of Medical Devices
Regulatory division of medical devices: class I, II and III
• more regulation for devices that pose greater risk
• Class I (General controls)
•
Manufacturers are required to perform registration, premarketing notification,
record keeping, labeling, reporting of adverse experiences and good
manufacturing practices
• Class II (Performance standards) 800 standards needed to be met
• Class III (Premarketing approval )
•
Manufacturers have to prove the safety of these devices prior to market
release
• Implanted devices (pacemakers etc.) are typically designated class III
• Investigational devices are typically exempt