biomedical instrumentation

01
Credit: 3 Hrs/week
Course conducted by:
Md. Mahmudul Haque Milu
Lecturer
Dept. of Biomedical Engineering,
Jashore University of Science and Technology
2/4/2023
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BIOMEDICAL INSTRUMENTATION
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 Biomedical instrumentation is a sub branch of biomedical engineering
which focuses on how electronics equipment can measure
physiological parameters of patient and improve medical care. It
involves diagnosis, treatment and prevention of disease in human.

GENERALIZED MEDICAL INSTRUMENTATION SYSTEM
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 Measurand:
Physical quantity, property, or condition that is being measured by the
system.
Accessibility:
- internal (blood pressure), on body surface (ECG, EEG)
- emanate from the body (infra-red radiation)
- derived from a tissue sample (blood or biopsy)
 Transducer:
Transducer is a device that converts one form of energy to another. The sensor
(part of a transducer) only senses the form of energy presence in the body.
Many transducer have a primary sensing element such as diaphragm which
converts pressure to displacement. Strain gauge that converts displacement to
electric voltage.

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 Signal conditioning:
Usually the sensor output can not directly drive the display, therefore
signal processing or conditioning is required.
Examples of signal processing:
1. Impedance matching
2. Amplification
3. Filtering
4. Mathematical mapping
5. Analog-to-digital conversion (ADC)
6. Signal averaging to reduce noise
7.Transformation (time domain to frequency domain)

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 Output display:
Examples of output displays:
1. Numerical
2. Graphical
3. Discrete
4. Continuous
5. Permanent or temporary
• Most displays rely on our vision, but auditory sense is also sometimes used.

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 Auxiliary elements:
*Calibration signal with the properties of the measurand should be applied to
the sensor input or as early in the signal processing chain as possible
**Many forms of feedback (automatic or manual) may be required to elicit the
measurand, to adjust the sensor and signal conditioner and to direct the flow of
output (display, storage, transmission)
***Data storage for signal conditioning or examination of alarm conditions or
implementation of different processing algorithms
**** Data communication transmission of patient data to remote display at
nurse’s station and medical center.

APPLICATIONS OF BIOMEDICAL INSTRUMENTS
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 Diagnostic purpose: ECG, EMG, EEG
 Therapeutic purpose: Pacemaker, Defibrillator, Incubator
 Clinical lab instruments: Gas analyzer, Spectrophotometer, Chemical
analyzer.

CLASSIFICATION OF BIOMEDICAL INSTRUMENTS
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 Based on the quantity that is sensed: pressure, flow, temperature, etc.
 Based on the principle of transduction: resistive, inductive, capacitive,
ultrasonic, electrochemical, etc.
 Based on the organ system: cardiovascular, pulmonary, nervous, endocrine,
etc.
 Based on the clinical medicine specialties: pediatrics, obstetrics, cardiology,
radiology instruments etc.

GENERALIZED STATIC CHARACTERISTICS
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 Accuracy:
Accuracy is the measure of the total error.
True or reference value varies with the normal range and frequency of inputs.
It is expressed by %.
 Precision:
Number of distinguishable alternatives from which a given result is selected.
High precision does not necessarily implies high accuracy.
For example, a meter shows 2.432 V is higher precise than a meter which
shows 2.43 V.

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 Resolution
Smallest incremental quantity that can be measured with certainty. Resolution
expresses the degree to which nearly equal two values of a quantity can be
discriminated.

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 Reproducibility or repeatability
Ability to give the same output for equal inputs applied over some period of
time
 Calibration
Calibration is the comparison of measurement values delivered by a device
under test with those of a calibration standard of known accuracy.
The outcome of the comparison can result in one of the following:
• no significant error being noted on the device under test
• a significant error being noted but no adjustment made
• an adjustment made to correct the error to an acceptable level

GENERALIZED DYNAMIC CHARACTERISTICS
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COMMERCIAL MEDICAL INSTRUMENTATION DEVELOPMENT PROCESS
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REGULATIONS FOR BIOMEDICAL DEVICES
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Classes of medical devices

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Most class I and some class II devices are exempt from review if they are extremely low
risk or very similar to existing devices. These exempt devices still must comply with
manufacturing and quality control standards.
Class II devices usually undergo a 510(k) review, which focuses on determining whether
the new device is “substantially equivalent” to an existing device. 510(k) reviews usually
do not require clinical trials to demonstrate substantial equivalence.
Manufacturers of class III devices submit a premarket approval (PMA) application. In
reviewing the application, FDA experts decide whether the new device is safe and
effective for treating a specific disease or condition. The PMA process must include
results from clinical studies, though the specific study design varies depending on the
device. For minor changes to existing class III devices, PMA supplements are submitted
instead of a full PMA. The use of PMA supplements for cardiac implantable electronic
devices is described in an article in the January 22/29, 2014, issue of JAMA.
https://jamanetwork.com/journals/jama/fullarticle/1817798
https://www.fda.gov/medical-devices/overview-device-regulation/classify-your-medical-device

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510(k) Clearances
Section 510(k) of the Food, Drug and Cosmetic Act requires device manufacturers
who must register, to notify FDA of their intent to market a medical device at least
90 days in advance. This is known as Premarket Notification - also called PMN or
510(k). This allows FDA to determine whether the device is equivalent to a device
already placed into one of the three classification categories. Thus, "new" devices
(not in commercial distribution prior to May 28, 1976) that have not been
classified can be properly identified. Specifically, medical device manufacturers
are required to submit a premarket notification if they intend to introduce a
device into commercial distribution for the first time or reintroduce a device that
will be significantly changed or modified to the extent that its safety or
effectiveness could be affected. Such change or modification could relate to the
design, material, chemical composition, energy source, manufacturing process,
or intended use.
https://www.fda.gov/medical-devices/device-approvals-denials-and-clearances/510k-clearances

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Premarket Approval (PMA)
Premarket approval (PMA) is the FDA process of scientific and regulatory review
to evaluate the safety and effectiveness of Class III medical devices. Class III
devices are those that support or sustain human life, are of substantial importance
in preventing impairment of human health, or which present a potential,
unreasonable risk of illness or injury. Due to the level of risk associated with
Class III devices, FDA has determined that general and special controls alone are
insufficient to assure the safety and effectiveness of Class III devices. Therefore,
these devices require a premarket approval (PMA) application under section 515
of the FD&C Act in order to obtain marketing approval.
https://www.fda.gov/medical-devices/premarket-submissions-selecting-and-preparing-correct-submission/premarket-approval-pma

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The PMA applicant is usually the person who owns the rights, or otherwise has
authorized access, to the data and other information to be submitted in support of
FDA approval. This person may be an individual, partnership, corporation,
association, scientific or academic establishment, government agency or
organizational unit, or other legal entity. The applicant is often the
inventor/developer and ultimately the manufacturer.
The regulation governing premarket approval is located in Title 21 Code of
Federal Regulations (CFR) Part 814, Premarket Approval of Medical Devices. A
Class III device that fails to meet PMA requirements is considered to be
adulterated under section 501(f) of the FD&C Act and may not be marketed.

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