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مقدمه: فصل اول

Medical Instrumentation

Dr. M.H.Moradi

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What is a Measurement?

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.اندازه گيري است ثر از توانايي انسان درأيشرفت علم و تكنولوژي متپ مطالعه :ايو دستگاههاي اندازه گيري، موضوعه ايلبدون دسترسي به وس

.مي شود سنجش ، طراحي و غيره بي مفهوم تحقيق ، ،

In the scientific method, a hypothesis is tested by experiment to determine its validity.

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Problemstatement

Reviewprior work

Statehypothesis

Performexperiments

Design furtherexperiments

Analyzedata

Finalconclusions

Moreexperimentsnecessary

Problemsolved

Purpose of Measurement Systems

The physician obtains the history, examines the patient, performs tests to determine the diagnosis and prescribes treatment.

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Chiefcomplaint

Obtainhistory

List thedifferentialdiagnosis

Examinationand tests

Select furthertests

Use datato narrow the

diagnosis

Finaldiagnosis

More thanone likely

Only onelikely

Treatmentand

evaluation

InstrumentPatient

InstrumentPatient

Clinician

(a) (b)

(a) Without the clinician, the patient may be operating in an ineffective closed loop system. (b) The clinician provides knowledge to provide an effective closed loop

system.

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InstrumentPatientClinician

Abnormalreadings

In some situations, a patient may monitor vital signs and notify a clinician if abnormalities occur.

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:اهداف اندازه گيري درپزشكي

اندازه گيری پديده ها برای شناخت سيستم: جمع آوري اطالعات

.....تشخيص بيماريها، ناهنجاريهای بيولوژيکی و: تشخيص

تم برای بدست آوردن اطالعات پيوسته از سيس: مونيتورينگ

تنظيم رفتار سيستم : درمان و كنترل

:ارزيابي

The fundamental purpose of a medical instrument is to enhance

the capabilities of human beings to help themselves and each other.

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:

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• A device that measures physiological parameter(s) such as pressure, flow, pulse, analyteconcentration, or temperature

• Examples– Thermometer– Blood Pressure– Pulse Oximeter– Glucose Monitor

Sensing/Monitoring

Types of Instruments:

• A device that gathers information leading to the identification of a disease or disorder

• Examples– Imaging (X-Ray, CT, MRI,PET)– Chemical Analyzers– Optical Diagnostics– DNA MicroArrays

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Diagnostic

• 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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Types of Instruments:Therapeutic

تاريخچهديدج حوزه سيستم ها و دستگاههاي اندازه گيري پزشكي چندان

در قرن Einthovenالكتروكارديوگرافي بوسيله .نمي باشد.نوزدهم ساخته و مورد استفاده قرار گرفت

اتزپيشرفت در اين زمينه تا بعد از جنگ جهاني دوم كه تجهي ر شدند، الكترونيكي نظير تقويت كننده ها و ثبات ها دسترس پذي

بسياري از تكنسين ها و مهندسان شروع 1950دردهه . كند بودي تجهيزات صنعتي موجود براي كاربردها حاصالو يش آزما به

.نمودند كه اغلب نتايج آنها مأيوس كننده بود پزشكي

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Riva-Rocci’s sphygmomanometer, 1896

Blood pressure measurement using Korotkov’s method, 1905

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Historical Evolution of Bioinstrumentation

Centuryth20Historical Perspective: • 1903 ECG – heart diagnostic

• 1924 EEG – brain waves

• 1928 ESU – cauterizing scalpel

• 1928 Iron Lung – respiration assist

• 1936 Nuclear Medicine

• 1956 Defibrillation

• 1957 Pacemaker (1960 implantable)

• 1957 Ultrasound Imaging(anatomical imaging)

• 1970 CT Scanner (anatomical imaging)

• 1975 Inter aortic balloon pump

• 1982 MRI (anatomical imaging)

• 1984 Artificial Heart

• 1990s PET - use radio isotopes (physiological imaging)

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نتايج حاصل از آزمايشات

يكي، روشن گرديد كه بسياري از پارامترهاي فيزيولوژ پارامترهاي فيزيكي اندازه گيري همانگونه كه

.دمي شوند، قابل اندازه گيري نمي باش

Apollo و Mercury ،Geminiي آمريكا نظير يبسياري از برنامه هاي فضا اندازه گيريهاي دقيق و صحيح پارامترهاي فيزيولوژيكيبه نياز

مر فضانوردان داشت و لذا بسياري از تحقيقات و بودجه ها به اين ا .اختصاص يافت

رها اندازه گيري اين پارامت تحليل و طراحي تجهيزات براين اساس

نه با اصالح دستگاههاي موجود براي(انجام گرفت ستقيماً م .و نتايج بسيار مثبت شد) اندازه گيري پارامترها صنعتي

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Historical Perspective: 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 (shown: Cammann Stethoscope circa 1880)

• Current research on use of acoustic transducer for stenosis diagnostics

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• 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

• Current developments includethe use of “light” outside the visible spectrum for imaging

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Historical Perspective: Use of Senses

• Taste and Smell have beenused to diagnose body fluids and wounds

• Urine of diabetics tastes sweet

• Clinical chemistry labs provide sample analysis in hospitals

• Current developments include electronic nose/taste sensors with arrays of individual sensors

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Historical Perspective: Use of Senses

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در يك سيستم زندهمحدوديتها و مشكالت اندازه گيري

دسترس ناپذير بودن اغلب متغيرها براي اندازه گيري

فقدان معرفت درباره روابط داخلي

اندركنش بين ارگانهاي مختلف بدن

اغتشاش

محدوديت پاسخ فركانسي و كوچك بودن دامنه خروجي

Iceberg Principle

10% is visible

90% is invisibleComplex Interactions

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AutnonomousNervousSysetm

CardiacElectricalSystem

CardiacMechnical System

VascularMechnical

Systemaction potentials

RespiratorySystem

(thoracicpressure)

HormonalSystem

(Epinephrine,Insulin)

blood flow

contractilitycompliance

preload, afterloadpacemaker rate

resistancecompliance

Electrocardiogram

Echocardiogram/Doppler

Phonocardiogram

Pressurewave

arterial pressurevenous pressure

venous return

Multi-System Interactions

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Oxy-hemoglobin saturation by pulse oximetry

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A typical measurement system uses sensors to measure the variable, has signal processing and display, and may provide feedback.

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كياجزاء معمول در يك سيستم اندازه گيري بيولوژي

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Sensors and Transducers

• Sensor –

• Transducer –

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Sensor is a Transducer:What is a transducer?

A device which converts one form of energy to another

ActuatorsSensors

Physical parameter

Electrical Output

Electrical Input

Physical Output

e.g. Piezoelectric:

Force -> voltage

Voltage-> Force

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Transducer• Sensor plus pre-processing/

amplifier• Transform physiological signal into

a form that the signal processor can read

• Must have good sensitivity and accuracy

• Should have low noise and sufficient dynamic range

• Must be effective and stable across entire physiological range

• Sensor can range from nanoscale structures to room-sized devices

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Signal Conditioning

Amplification• Amplification is the set of

techniques used to boost a signal'sstrength to better match theanalog-to-digital converter (ADC)range

• Increases the measurementresolution and sensitivity.

• Improves the signal-to-noise ratio.

Signal Processor• Can be as simple as driving a

needle meter or a level on a scale OR as complex as a computer reconstructing a three dimensional image from thousands of pictures

• The use of electronic signal processors has enabled numerous advances in the past four decades

• “Heavy duty” mathematical processing is becoming the norm

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Feedback• Traditionally involved a

physician or therapist observing the patient

• More recently feedback occurs in a “closed loop” with sensor(s) and/or monitor(s)

• FDA is very careful to maintain human involvement in important decision processes

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Measurement Range Frequency, Hz Method

Blood flow 1 to 300 mL/s 0 to 20 Electromagnetic or ultrasonic

Blood pressure 0 to 400 mmHg 0 to 50 Cuff or strain gage

Cardiac output 4 to 25 L/min 0 to 20 Fick, dye dilution

Electrocardiography 0.5 to 4 mV 0.05 to 150 Skin electrodes

Electroencephalography 5 to 300 V 0.5 to 150 Scalp electrodes

Electromyography 0.1 to 5 mV 0 to 10000 Needle electrodes

Electroretinography 0 to 900 V 0 to 50 Contact lens electrodes

pH 3 to 13 pH units 0 to 1 pH electrode

pCO2 40 to 100 mmHg 0 to 2 pCO2 electrode

pO2 30 to 100 mmHg 0 to 2 pO2 electrode

Pneumotachography 0 to 600 L/min 0 to 40 Pneumotachometer

Respiratory rate 2 to 50 breaths/min 0.1 to 10 Impedance

Temperature 32 to 40 °C 0 to 0.1 Thermistor

Common medical Misbrands.

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Specification Value

Pressure range –30 to +300 mmHg

Overpressure without damage –400 to +4000 mmHg

Maximum unbalance ±75 mmHg

Linearity and hysteresis ± 2% of reading or ± 1 mmHg

Risk current at 120 V 10 A

Defibrillator withstand 360 J into 50

Sensor specifications for a blood pressure sensor are determined by a committee composed of individuals from academia, industry, hospitals, and government.

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Laboratory test Typical value

Hemoglobin 13.5 to 18 g/dL

Hematocrit 40 to 54%

Erythrocyte count 4.6 to 6.2 106/ L

Leukocyte count 4500 to 11000/ L

Differential count

Neutrophil 35 to 71%

Band 0 to 6%

Lymphocyte 1 to 10%

Monocyte 1 to 10%

Eosinophil 0 to 4%

Basophil 0 to 2%

Complete blood count for a male subject.

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مالكها و معيارهايطراحي

دامنه كميتي كهبايد

.اندازه گيري شود

مالحظات اقتصادي

محل بكارگيري مبدل روي

بدن مريض در كوتاه مدتو درازمدت

مشخصه ايستا وپوياي

فرآيند تحت بررسي

مرتبه صحت و دقت

مورد نياز

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Static sensor characteristics• Sensitivity

– Ratio: Output amplitude/Input amplitude• Range

– Valid range of input signal from most negative to most positive amplitude value.

• Precision– Precision refers to the degree of reproducibility. Even for a

constant input the output fluctuates about a mean value. High precision means small fluctuation (small standard deviation).

• Resolution– The smallest detectable incremental change in the input

signal that can be detected in the output signal.• Accuracy

– Maximum difference between actual and indicated value.• Offset

– The output that will exist when it actually should be zero.

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درستي و دقت در اندازه گيري:(accuracy)) صحت(درستي •

.مقدار واقعيميزان نزديك بودن اندازه ها به

:(precision)دقت •.همديگرميزان نزديك بودن اندازه ها به

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it is a necessary but not sufficient condition for accuracy

Accuracy vs. Precision

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Frequency response of the electrocardiograph.

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0.05 Hz 150 Hz

Frequency

Amplitude

1.0

0.1

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Dynamic Characteristic

First-order system

ExponentialTime constant

System

Second-order system

Natural frequencyUnder-dampingCritical-dampingOver-damping

Transient response System behavior

Dependence of the system behavior on the value of the damping ratio ζ, for under-damped, critically-damped ,over-damped, and undamped cases, for zero-velocity initial condition. The behavior of the system depends on the relative values of the two fundamental parameters, the natural requency ω0and the damping ratio ζ. In particular, the qualitative behavior of the system depends crucially on whether thequadratic equation for γ has one real solution, two real solutions, or two complex conjugate solutions.

Dynamic sensor characteristics• Dynamic response time

– The ability of a sensor to quickly settle at a new value when the input signal is changed abruptly.

Rise time

Delay time

Time to peak

Settling time

Step response

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Dynamic sensor characteristics

nd

nr

np

ns

t

t

ePO

t

t

2

2

1/

2

469.0125.01.1

917.24167.01

100

1

4

2

Settling time:

Time to peak:

% overshoot:

Rise time:

Delay time:

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Critical damping (ζ = 1)

When ζ = 1, there is a double root γ (defined above), which is real. The system is said to be critically damped. A critically damped system converges to zero faster than any other, and without oscillating.

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فرآيند توليد دستگاهاي پزشكي

كميت تحت اندازه گيري

فاكتورهايسيگنال

فاكتورهاي محيطي

فاكتورهايطبي

فاكتورهاياقتصادي

ورودي مطلق يا ديفرانسيلي -رنج -حساسيت-اسخ فركانسي گذراپ -وروديدانسپام

قابليت اعتماد -خطي بودن -صحت

درجه حرارت -ايداريپ -نسبت سيگنال به نويزلرزش -شوك -شتاب -فشار -رطوبت

شكل -توان مورد نياز -تشعشعشرايط مورد نياز براي نصب

مجاز بودن -در دسترس بودن -قيمتضمانت داشتن اجزاء مصرفيسازگاري با تجهيزات موجود

طراحي اوليه سيستم

شبيه سازي

ساخت و آزمايشنمونه اوليه

طراحي نهاييسيستم

رعايت استانداردFDA,BMD

توليد

-يا سطحي) نيازمند جراحي(نوع تهاجمي -بافت -نيازمنديهاي واسطه مبدل

موادسميي ايمن(سالمت بودن از نظر الكتريكي

)الكتريكيراحتي مريض -تشعشع و گرما

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SLIET, Longowal

Automation in Biomedical

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