Medical Instrumentations

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Fundamentals of 

Medical Instrumentations

The fundamental purpose of a medical

instrument is to enhance the capabilities of 

human beings to help themselves and

each other.

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What is a Medical Instrument?

Definition: Device including

instrument, tool, machine or 

implant for monitoring or 

sensing, diagnostics, or therapeutics or surgery

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Types of Instruments:

1. Sensing/Monitoring� A device that measures physiological

parameters such as pressure, flow, pulse,

analytic concentration, or temperature� Examples

± Thermometer 

± Blood Pressure

± Pulse Oximeter 

± Glucose Monitor 

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Types of Instruments:

2. Diagnostic� A device that gathers

information leading to the

identification of a disease or 

disorder � Examples

± Imaging (X-Ray, CT, MRI, PET)

± Chemical Analyzers (Clinical

Chemistry)± Optical Diagnostics DNA

MicroArrays

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Types of Instruments:

3. Therapeutic� A device that is used to treat a disease or disorder.

� Examples include:

± Simple crutch± Drug delivery

± Surgical Tools (scalpel, laser)

± Orthopedic implants

± Soft tissue implants

± Pacemakers

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Basic Generic Instrument

Biological

SystemTransducer 

Signal

Processor 

Sensing/

Monitoring

Diagnosis

Therapeutics/

Surgery

Feedback

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Transducer 

� Sensor plus pre-processing/amplifier 

� Transform physiological signal intoa form that the signal processor 

can read� Must have good sensitivity andaccuracy

� Should have low noise andsufficient dynamic range

� Must be effective and stableacross entire physiological range

� Sensor can range from nanoscalestructures to room-sized devices

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Signal Processor 

� Can be as simple as driving aneedle meter or a level on a scaleor as complex as a computer reconstructing a threedimensional image fromthousands of pictures

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Feedback

� Traditionally involved a

physician or therapist

observing the patient

� More recently feedback

occurs in a ³closed loop´

with sensors and/or 

monitors

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Use of Senses

� Touch/Hearing used to

quantify temperature,

pulse rate, and heart beat

as well as therapy

� Stethoscope invented in

1819 to enhance sounds.

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Use of Senses

� Sight used on both the inside

and outside of the body

� Candles and magnifiers used� Ophthalmoscope used to probe

ears, eyes and nose

� Endoscope probes deeper in

body where there is no light

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Use of Senses

� Taste and Smell have been

used to diagnose body fluids

and wounds

� Urine of diabetics tastes sweet

� Clinical chemistry labs provide

sample analysis in hospitals

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