Ch 01 Basic Concepts of Medical Instrumentation - PowerPoint Presentation

Slide1

Ch 01 Basic Concepts of Medical InstrumentationSlide2

1.1 Terminology of Medicine and Medical Devices

Type

Dictionary

Homepage

English-Chinese Medical Dictionary

榮陽數位化醫學字典

由台北榮民總醫院及陽明大學合作建立的數位化醫學辭典。可查詢中文及英文醫學字彙。

http://libs2.vghtpe.gov.tw/digital_new/portal_d1.php?button_num=d1

English-Chinese Dictionary

YAHOO

奇摩字典

https://tw.dictionary.yahoo.com/

English-

Indonessian

Medical Dictionary

(To

be found)

(To

be found)Slide3
Slide4

1.2 Generalized Medical Instrumentation SystemSlide5

Figure 1.1 Generalized instrumentation system

The sensor converts energy or information from the

measurand

to another form (usually electric). This signal is the processed and displayed so that humans can perceive the information. Elements and connections shown by dashed lines are optional for some applications.

Perceptible

output

Output

display

Control

And

feedback

Signal

processing

Data

transmission

Data

storage

Variable

Conversion

element

Sensor

Primary

Sensing

element

Measurand

Calibration

signal

Radiation,

electric current,

or other applied

energy

Power

source

(Display, printer, etc.)

(Transducer)

Transducer :

enrgy

1

 energy 2Slide6

Measurand

Accessibility

Internal

On body surface

Emanate

from the body

Derived from a tissue sample

Categories

Biopotential

Pressure

Flow

DimensionImagingDisplacement (velocity, acceleration, force)Impedance

TemperatureChemical concentration

measurand [′mezh·ə‚rand]

(science and technology) A quantity that is to be measured.McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.Slide7

1.3 Alternative Operational Modes

Direct-indirect modes

Direct: The

measurand

is accessible.

Indirect: The

measurand

is inaccessible. E.g.: cardiac output (blood volume/min from the heart), morphology of internal organs, pulmonary volumeCardiac : heart

Sampling and continuous modesCan be sampled infrequently: e.g., body temperature, ion concentration Must be monitored continuously: e.g., respiratory gas flow, ECG

Generating and modulating sensors Generating sensors: produce their signal output from energy taken directly from the

measurand; e.g., photovoltaic cell* Modulating sensors: use the measurand to alter the flow of energy from an external source in a way that affects the output of the sensor; e.g., photoconductive cell

Analog and digital modes * Analog: able to take on any value within the dynamic range * Digital: accuracy, repeatability, reliability, noise-immunity, not requiring periodic calibrationReal-time and delayed-time modes

Acquire or display the result in real time: when urgent feedback and control tasks depend on the outputAcquire or display the result in delayed time: e.g. cell cultureSlide8

photovoltaic

cell vs. photoconductive cell

http://allineee.blogspot.tw/2011_09_01_archive.html

http

://www.technologystudent.com/energy1/solar5.htm

Generating

modulatingSlide9

1.4 Medical Measurement Constraints

Biomedical signal parameters ---- low (compared with

nonbiomedical

ones)

e.g., potential =



V



mV frequency = DC100 Hz

pressure ~ 100 mm HgInaccessibility of many crucial variables in living systems

e.g., cardiac output is quite inaccessible.Physical sizes of many sensors --- prohibits the formation of a proper

measurandsensor interface

Difficult to establish safe level of energy (e.g., X-ray, ultrasound, etc.) -- many mechanisms of tissue damage are not well understood. -- heating of tissue must be limited (I^2 * R = V^2/R) -- Damage to tissue at molecular level can be caused at surprisingly low energy levels.

Operation of instruments in the medical environment imposes important constrains

-- Equipment must be reliable, easy to operate, and capable of withstanding physical abuse and exposure to corrosive chemicals

-- Electronic equipment must be designed to minimize electric-shock hazards -- must consider the safety of patients and medical personnel

Is it good to be this low?

Is it good to be this low?Slide10

Ballistic =

彈道的

Gastric

=

胃的

Antimony

=

Sb, 銻Slide11

galvanic skin response definition

Function:

:

 a change in the electrical resistance of the skin that is a physiochemical response to emotional arousal which increases sympathetic nervous system activity — abbreviation

GSR

Merriam-Webster's Medical Dictionary, © 2007 Merriam-Webster, Inc.

Source:

Dictionary.com, "galvanic skin response," in

Merriam-Webster's Medical Dictionary

. Source location: Merriam-Webster, Inc.

http://dictionary.reference.com/browse/galvanic skin response. Available: http://dictionary.reference.com. Accessed: February 23, 2011.

a change in the electrical resistance of the skin occurring in moments of strong emotion; measurements of this change are used in lie detector tests GSRSlide12

s

pneumo

- or

pneum

-

pref.

1. Air; gas

: pneumothorax 氣胸.2.

Lung; pulmonary: pneumoconiosis 塵肺病.

3. Respiration: pneumography a.肺解剖學. b.呼吸運動描記法

. c.充氣X光線照像.

Pneumotachography 呼吸氣速度描記.4.

Pneumonia: pneumococcus

肺炎雙球菌,Slide13

To cope variability

 use assume empirical

statistical

and probabilistic distribution functions

Variability of measured quantities:

with time,

among patients,

anatomical

？

, interactions among physiological systems,

feedback loops, internal variability (at molecular and organ levels), …Slide14

1.5 Classification of Biomedical Instruments

According to what?

Examples

Quality that is sensed

Pressure, flow, temperature,

Transduction

Resistive (I

 V)

, inductive

( -> ),

capacitive

(V

 Q

), ultrasonic (structure or motion  ultrasound) , electrochemical (concentration

 electrochemical

reaction)

Organ systemCardiovascular, pulmonary, nervous, endocrine

Clinical medicine specialties

Pediatrics, obstetrics (產科),

cardiology, radiology

Different classifications:

Transducer: converting one energy type to another one

C

R = V/I

L = V/(di/

dt

)

C = Q/VSlide15

1.6 Interfering and Modifying InputsSlide16

Figure 1.2 Simplified electrocardiographic recording system

Two

possible interfering inputs are stray magnetic fields and

capacitively

coupled noise.

Orientation

of patient cables and changes in electrode-skin impedance are two possible modifying inputs.

Z

1

and

Z

2 represent the electrode-skin interface impedances.

Electrodes

60-Hz

ac magnetic

field

Displacement

currents

Differential

amplifier

+

-

+

V

cc

-

V

cc

Z

1

Z

body

Z

2

v

o

v

ecgSlide17
Slide18

1.7 Compensation Techniques

How to reduce or eliminate the effects of interfering and modifying inputsSlide19

Techniques

Examples

Inherent insensitivity

Magnetic

interference on ECG:

Twisting the electrode wires

Electrode motion :

(see Section 5.5)

Negative feedback

y =

xd

x Gd

/(1 + Hf Gd)Signal filtering

Opposing inputs

Thermistors  Temperature-dependence

of other devicesSlide20

1.8 BiostatisticsSlide21
Slide22

1.9 Generalized Static Characteristics

Accuracy

Precision

Resolution

Reproducibility

Statistical control

To tolerate random variations;

By averaging;

Static sensitivity

Zero drift

Sensitivity drift

Linearity

Input range

Input impedanceSlide23

Static sensitivity :

(the incremental output

quntity

)/(the incremental input quality)

Example: the static sensitivity of strain-gage blood-pressure sensor

50 

V  V

1 mmHg 1

Slide24

Figure 1.3

(a)

Static-sensitivity

curve that relates desired input

x

d

to output

y

. Static sensitivity may be constant for only a limited range of

inputs.

Intercept

b

D

x

d

D

y

D

x'

d

D

y'

y

(Output)

y = mx

d

+

b

x

d

(Input)

(a)

Slope

m

=

D

y

D

x

d

Calibration:

(

1.11

)

(1.9)

(1.10)Slide25

Figure 1.3

(b

) Static sensitivity: zero drift and sensitivity drift. Dotted lines indicate that zero drift and sensitivity drift can be negative

.

Total error due to drift

Characteristic with zero and sensitivity drift

+ Zero

drift

+ Sensitivity

drift

-

Sensitivity drift

-

Zero drift

(b)

y

(Output)

x

d

(Input)

zero

drift; sensitivity driftSlide26

Linearity

Definition of linearity:

x

1

(

x

1

+

y

2

)

y

1

x

2

Kx

1

Ky

1

y

2

Linear

system

Linear

system

Linear

system

Linear

system

and

and

(

y

1

+

y

2

)Slide27

Figure 1.4

(a) Basic definition of linearity for a system or element. The same linear system or element is shown four times for different inputs. (b) A graphical illustration of independent

nonlinearity

equals



A% of the reading, or



B% of full scale, whichever is greater (that is, whichever permits the larger error).

(a)

(b)

x

d

(Input)

B% of full scale

A% of reading

Overall tolerance band

Least-squares

straight line

Point at which

A% of reading = B% of full scale

y

(Output)Slide28

(Generalized) input impedance

Z

x

(1.12)

(1.13)Slide29

1.10 Generalized Dynamic CharacteristicsSlide30

(1.14)

(1.15)

(1.16)

(1.17)Slide31

Figure 1.5

(a) A linear potentiometer, an example of a zero-order system.

(

b) Linear static characteristic for this system.

(

c) Step response is proportional to input.

(

d) Sinusoidal frequency response is constant with zero phase shift.

Zero-order instrumentSlide32

(1.18)

(1.19)Slide33

Figure 1.6

(a) A low-pass

RC

filter, an example of a first-order instrument.

(

b) Static sensitivity for constant inputs.

(

c) Step response for larger time constants (



L

) and small time constants (



S).

(

d) Sinusoidal frequency response for large and small time constants.

Output

y

(

t

)

Input

x

(

t

)

Slope =

K

= 1

(b)

(d)

0°

-

45°

-

90°

Log scale

w



L



S

f

Y

(

j

w

)

X

(

j

w

)

Log

scale

1.0

0.707

Log scale

w

w

S

w

L



L



S

(c)

t

1

y

(

t

)

x

(

t

)

t

1

0.63



L



S

y

(

t

)

(a)

C

+

-

+

-

y

(

t

)

x

(

t

)

R

First-order instrumentSlide34

(1.20)

(1.21)

(1.22)

(1.23)

(1.24)Slide35

Figure 1.7

(

a) Force-measuring spring scale, an example of a second-order instrument.

(

b) Static sensitivity.

(

c) Step response for overdamped

case,



=

2;

critically damped

case,



= 1; underdamped case,



= 0.5.

(

d) Sinusoidal steady-state frequency response, 

= 2,



= 1, 

=

0.5.

Output

y

(

t

)

(b)

Input

x

(

t

)

Slope

K

=

1

K

s

(c)

x

(

t

)

1

t

1

K

s

y

(

t

)

y

n

y

n + 1

0.5

1

2

t

(d)

Resonance

2

Log

scale

1

0.5

Log scale

w

K

w

n

Y

(

j

w

)

X

(

j

w

)

2

-90°

-180°

1

0.5

Log scale

w

0

°

w

n

f

Output

displacement

(a)

Input

Force

x

(

t

)

0

y

(

t

)

Second-order instrumentSlide36

where

(1.25)

(1.26)

(1.27)

(1.28)Slide37

Overdamped,

Underdamped,

Critically damped,

(1.29)

(1.30)

(1.31)

(1.32)

(1.33)

(1.34)

(1.35)Slide38

and

(1.36)

(1.37)

(1.38)

(1.39)

(1.40)Slide39
Slide40

1.11 Design CriteriaSlide41

Figure 1.8 Design process for medical

instruments

BMD =

骨質密度

(Bone Mineral Density) ?

BMD =

bacitracin

methylene

disalicylate(桿菌呔次甲基)

What is “specificity”?

Why “acceleration”?

Chapter 14Slide42

1.12 Commercial Medical Instrumentation Development ProcessSlide43
Slide44

1.13 Regulation of Medical DevicesSlide45

Classification of Medical

Devices (Taiwan)

藥事法 第

13

條

本法所稱

醫療器材

，係包括診斷、治療、減輕或直接預防人類疾病，或足以影響人類身體結構及機能之儀器、器械、用具及其附件、配件、零件。 前項醫療器材，中央衛生主管機關應視實際需要，就其範圍、種類、管理 及其他應管理事項，訂定醫療器材管理辦法規範之。

醫療器材管理辦法 第

2

條

醫療器材依據風險程度，分成下列等級： 第一等級：低風險性。

第二等級：中風險性。 第三等級：高風險性。 Slide46

Categories of Medical Devices (Taiwan)

醫療器材管理辦法第

3

條

醫療器材依據功能、用途、使用方法及工作原理，分類如下：

一、臨床化學及臨床毒理學。

(Clinical chemistry and toxicology devices)

二、血液學及病理學。

(Hematology and pathology devices)

三、免疫學及微生物學。 (immunology and microbiology devices)四、麻醉學。

(Anesthesiology devices)五、心臟血管醫學。 (Cardiovascular devices)六、牙科學。 (Dental devices)

七、耳鼻喉科學。(Ear, nose , and throat devices) 八、胃腸病科學及泌尿科學。 (Gastroenterology-Urology devices)九、一般及整形外科手術。

(General and plastic surgery)十、一般醫院及個人使用裝置。 (General hospital and personal use devices)十一、神經科學。

(Neurological devices)十二、婦產科學。 (Obstetrical and gynecological devices)

十三、眼科學。 (Ophthalmic devices)十四、骨科學。 (Orthopedic

devices)十五、物理醫學科學。 (Physical medicine devices)十六、放射學科學。

(Radiology devices)十七、其他經中央衛生主管機關認定者。 前項醫療器材之分類分級品項如附件一。

(Other categories specified by the Central Competent Health Authority)Slide47

FDA Classification (USA)

在美國的分級，分級原則是規定於

FD&C Act

第

513

節，分成三級：

l

        Class I

一般管制  這些器材只要經過一般管制就可以確保其功效與安全性，如拐杖、眼鏡片、膠布等，約佔全部醫療器材的

27%。這些管制包括：禁止粗製濫造及不當標示的產品銷售；FDA得禁止不合格產品銷售；必須報告

FDA有關危害性、修理、置換等事項；限制某些器材的販賣、銷售、及使用；實施GMP

；要求國內製造商、進口商及銷售者都要向FDA註冊，製造者須列明所製造的產品。Class II及Class III同樣要遵守以上要求。

  l        Class II

特別管制(Special Controls)  第一等級的醫療器材這些產品除了上述一般管制之外，尚須符合FDA

所訂定的特別要求或其他工業界公認的標準，此類產品包含醫用手套、電動輪椅、助聽器、血壓計、診療導管等，約佔所有器材的60%。

FDA的特別要求之中，對特定產品另有強制性的標準(mandatory performance standards)、病患登記及上市後監督等。

 l        Class III

上市前許可   一般來說，Class III

的產品多為維持、支持生命或植入體內的器材，對病患具有潛在危險，可能引起傷害或疾病者，如心律調節器、子宮內器材及嬰兒保溫箱等，約佔所有器材的8%

。這些器材必須取得FDA的PMA之後方能銷售。

Source:

弘亞生技Slide48

1930s

Federal Food, Drug, and Cosmetics Act

May 28, 1976

Medical Device Amendments

Classes I, II, III

7 Categories

1990

Safe Medical Devices Act

Further amendments

Purpose: To ensure the safety and efficacy of new medical devices prior to marketing of the deviceSlide49

“Medical Device” definition by FDA [Source: Wikipedia]

Definition in USA by the Food and Drug Administration

Medical Device

Definition

A device is:

"an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is:

-

recognized in the official National Formulary, or the United States Pharmacopoeia, or any supplement to them,

intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or

intended to affect the structure or any function of the body of man or other animals, and

which does not achieve any of it's primary intended purposes through chemical action

within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of any of its primary intended purposes.

Contrivance

發明物; 裝置

, 器械[C]Formulary

公式的, 規定的Pharmacopoeia

藥典; 配藥書Slide50

Medical Device (defined by FDA) [Source FDA website]

Medical Device Definition

Medical devices range from simple

tongue depressors

and

bedpan

s to complex programmable pacemakers with micro-chip technology and laser surgical devices. In addition, medical devices include in vitro diagnostic products, such as general purpose lab equipment,

reagent

s, and

test kits, which may include monoclonal antibody technology. Certain electronic

radiation emitting products3 with medical application and claims meet the definition of medical device. Examples include diagnostic ultrasound products, x-ray machines and medical lasers. If a product is labeled, promoted or used in a manner that meets the following definition in section 201(h) of the Federal Food Drug & Cosmetic (FD&C) Act it will be regulated by the

Food and Drug Administration (FDA)

4 as a medical device and is subject to premarketing and postmarketing regulatory controls.

Bedpan 便盆Slide51

Medical Device (defined by FDA) [Source FDA website]

Medical Device Definition

A device is:

"an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is:

 recognized in the official National Formulary, or the United States Pharmacopoeia, or any supplement to them,

intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or

intended to affect the structure or any function of the body of man or other animals, and which does not achieve any of it's primary intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of any of its primary intended purposes."

This definition provides a clear distinction between a medical device and other FDA regulated products such as drugs. If the primary intended use of the product is achieved through chemical action or by being metabolized by the body, the product is usually a drug. Human drugs are regulated by FDA‘s

Center for Drug Evaluation and Research

5

(CDER). Biological products which include blood and blood products, and blood banking equipment are regulated by FDA’s

Center for Biologics Evaluation and Research

6 (CBER). FDA‘s Center for Veterinary Medicine7 (CVM) regulates products used with animals. If your product is not a medical device but regulated by another Center in the FDA, each component of the FDA has an office to assist with questions about the products they regulate. In cases where it is not clear whether a product is a medical device there are procedures in place to use

DSMICA Staff Directory8 to assist you in making a determination.Slide52

FDA

Classification [Source: Wikipedia]

United States

The Food and Drug Administration has recognized three classes of medical devices based on the

level of control

necessary to assure the

safety and effectiveness

of the device.[7]

The classification procedures are described in the Code of Federal Regulations, Title 21, part 860 (usually known as 21 CFR 860).

[8]Class I: General controls

Class I devices are subject to the least regulatory control. Class I devices are subject to “General Controls” as are Class II and Class III devices.

General controls include provisions that relate to adulteration; misbranding; device registration and listing; premarket notification; banned devices; notification, including repair, replacement, or refund; records and reports; restricted devices; and good manufacturing practices.

Class I devices are not intended for use in supporting or sustaining life or to be of substantial importance in preventing impairment to human health, and they may not present a potential unreasonable risk of illness or injury

. Most Class I devices are exempt from the premarket notification and/or good manufacturing practices regulation.

Examples of Class I devices include elastic bandages, examination gloves, and hand-held surgical instruments

.Adulteration

粗劣品; 攙假貨Slide53

FDA

Classification (cont.) [Source: Wikipedia]

Class II: General controls with special controls

Class II devices are those for which

general controls alone are insufficient to assure safety and effectiveness, and existing methods are available to provide such assurances

.

In addition to complying with general controls, Class II devices are also subject to

special controls

.[9] A few Class II devices are exempt from the premarket notification.

[9] Special controls

may include special labeling requirements, mandatory performance standards and postmarket surveillance

.[9] Devices in Class II are held to a higher level of assurance than Class I devices, and are designed to perform as indicated without causing injury or harm to patient or user.

Examples of Class II devices include powered wheelchairs, infusion pumps, and surgical drapes.

[7][9]Class III: general controls and premarket approval

A Class III device is one for which

insufficient information exists to assure safety and effectiveness solely through the general or special controls sufficient for Class I or Class II devices.[7]

[9]

Such a device needs premarket approval, a scientific review to ensure the device's safety and effectiveness

, in addition to the general controls of Class I.[7][9]

Class III devices are usually 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.[9]

Examples of Class III devices which currently require a premarket notification include implantable pacemaker, pulse generators, HIV diagnostic tests, automated external defibrillators, and

endosseous (placed or contained within a bone) implants.

[9]

Drape

簾

Endosseous adj

refers to any object, such as a dental implant, placed or contained within a bone.Slide54

FDA Medical Device CategoriesSlide55

FDA Medical Device Categories (cont.)Slide56

Category:

Preamendment

devicesSlide57

Category:

Postamendment

devices

Fetoprotein

胎蛋白

; radioimmunoassay (RIA)

放射免疫測定

Radioimmunoassay

(RIA), an

in vitro

nuclear medicine, is a very sensitive technique used to measure concentrations of antigens

(for example, hormone levels in the blood) by use of antibodies. (Source: Wikipedia)

Extracorporeal shock wave lithotripsy (

ESWL) is the non-invasive

treatment of kidney stones (urinary calculosis

) and biliary calculi

(stones in the gallbladder or in the

liver) using an acoustic pulse. (Source: Wikipedia)Slide58

Category: Substantially equivalent devices

Tampon

止血棉球

,

月經棉塞

; ELISA (Enzyme-linked

immunosorbent

assay)

酵素連結免疫吸附法;Slide59

Category: Implanted devices

Phrenic

橫隔膜的Slide60

Category: Custom devicesSlide61

Category: Investigational devicesSlide62

Category: Transitional devices

Transitional

過渡性的

; Gonorrhea

淋病

; heterograft

異種移植片

An

intraocular lens

(IOL) is an implanted

lens in the

eye, usually replacing the existing crystalline lens because it has been clouded over by a

cataract, or as a form of refractive surgery to change the eye‘s optical power. [Source: Wikipedia]Slide63

From 3

rd

EditionSlide64

(

x

d

–

H

f

y

)

G

d

= y

(1.1) 

xdG

d =

y(1 +

Hf

Gd

) (1.2) 

(1.3) 

  (1.4)

(1.8)

(1.7)

(1.6)

(1.5)