致于欣立-2生物醫(yī)學(xué)電子學(xué)

醫(yī)

學(xué)20生13物－2醫(yī)01學(xué)4學(xué)電年子第學(xué)一學(xué)期生物醫(yī)學(xué)喬清理2013,08,28主要內(nèi)容電測量的優(yōu)點生物醫(yī)學(xué)測量系統(tǒng)的一般結(jié)構(gòu)生物醫(yī)學(xué)測量的特點（或約束）對測量系統(tǒng)的基本要求生物醫(yī)學(xué)測量趨勢測控系統(tǒng)的設(shè)計1.測量的概念與分類獲取傳輸處理控制…信息獲取是了解信息流組成，

疾病重要的的一環(huán)。測量的定義測量是為確定被測對象的量值而進行的實驗過程。測量結(jié)果＝測量數(shù)值*測量單位即：X=X0

*{X}廣義測量的定義廣義地講，測量不僅對被測的物理量進行定量的測量，而且還包括對更廣泛的被測對象進行定性、定位的測量。而測量結(jié)果也不僅僅是由量值和單位來表征的一維信息，還可以用二維或 的圖形、圖像來顯示被測對象的屬性特征、空間分布、 結(jié)構(gòu)等。根據(jù)所測量的參數(shù)，測量分為電量測量和非電量測量電量測量：心電信號，直接由電極拾??；非電量測量：血壓、體溫、呼氧等都需要通過各種傳感器拾取，然后轉(zhuǎn)換為與之有確定函數(shù)關(guān)系的電信號測量的分類2.電測法的優(yōu)點具有極精細的分辨力和很寬的測量范圍。采取電子技術(shù)，可以很方便地改變儀器的靈敏度和測量范圍。電子測量儀器具有極小的慣性。既能測量變化緩慢的量，又可測量快速變化的量。有利于信息傳遞。無論在時間上還是在空間上可以很方便地實現(xiàn)遙測。靈活的變化技術(shù)和各種運算和處理、顯示和記錄。。PerceptibleoutputOutputdisplayControlAndfeedbackCPUDatatransmissionDatastorageSignalConditiongSensorMeasurandRadiation,electric

current,or

otherappliedenergyCalibrationsignalPowersource3生物醫(yī)學(xué)測量系統(tǒng)的構(gòu)成原理框圖A/D生物醫(yī)學(xué)測量系統(tǒng)的構(gòu)成傳感器：非電量到電量的變換；

信號調(diào)理電路：阻抗變換，放大，濾除噪聲，抗混頻；動態(tài)范圍匹配A/D轉(zhuǎn)換：微處理器：信號處理，系統(tǒng)控制D/A轉(zhuǎn)換：MeasurandThe

object

of

a

measurement;The

measurand

is

the

desired

input

and

the

object

of

measurement.The ty,

property,

or

condition

that

is

measured

by

aninstrumentation

systemis

called

the

measurandMeasurand

can

be

a

bioelectric

signal,

such

as

those

generated

bymuscles

or

the

brain,

or

a

chemical

or

mechanical

signal

that

isconverted

to

an

electrical

signal.BiopotentialPressureFlowDimensions

(imaging)Displacement

(velocity,

acceleration,

force)ImpedanceTemperatureChemical

ConcentrationBiomedical

MeasurandMeasurementRangeFrequency,

HzMethodBlood

flow1

to

300

mL/s0

to

20Electromagnetic

orultrasonicBlood

pressure0

to

400

mmHg0

to

50Cuff

or

strain

gageCardiac

output4

to

25

L/min0

to

20Fick,

dye

dilutionElectrocardiography0.5

to

4

mV0.05

to150Skin

electrodesElectroencephalography5

to

300

V0.5

to

150Scalp

electrodesElectromyography0.1

to

5

mV0

to

10000Needle

electrodesElectroretinography0

to

900

V0

to

50Contact

lens

electrodespH3

to

13

pH

units0

to

1pH

electrodepCO240

to

100mmHg0

to

2pCO2

electrodepO230

to

100mmHg0

to

2pO2

electrodeP

otachography0

to

600

L/min0

to

40P

otachometerRespiratory

rate2

to

50breaths/min0.1

to

10ImpedanceTemperature32

to

40

°C0

to

0.1ThermistorPerceptibleoutputOutputdisplayControlAndfeedbackCPUDatatransmissionDatastorageSignalConditiongSensorMeasurandRadiation,electric

current,or

otherappliedenergyCalibrationsignalPowersource生物醫(yī)學(xué)測量系統(tǒng)的構(gòu)成原理框圖A/DSensor

and

TransducerTransducerA

device

that

converts

a

signal

from

one

physical

form

to

acorresponding

signal

having

a

different

physical

formPhysical

form:

mechanical,

thermal,

magnetic,

electric,

optical,chemical…Transducers

are

ENERGY

CONVERTERS

or

MODIFIERSSensorA

device

that

receives

and

responds

to

a

signal

or

stimulusThis

is

a

broader

concept

that

includes

the

extension

of

our

perceptiontiescapabilities

to

acquire

information

about

physicalTransducers:

sensors

and

actuatorsSensor:

an

input

transducer

(i.e.,

a

microphone)Actuator:

an

output

transducer

(i.e.,

a

loudspeaker)Signal

ConditioningAmplifier:electronic

amplifier

amplifies

the

output

of

the

primary

transducer

orvariable

conversion

element,

thus

improving

the

sensitivity

andresolution

of

measurement.

This

element

of

a

measuring

system

isparticularly

important

where

the

primary

transducer

has

a

low

output.For

example,

EEG

electrodes

have

a

typicaloutput

of

only

a

fewmillivolts.FilterA

device

or

program

that

separates

data,

signals,

or

material

inaccordance

with

specified

criteria.Impedance

matchogto

Digital

(A/D/A)Average

(reduce

noise)Time

→

Frequency

(Spectrumysis)A/DTheReal

World

is

ogAn

og-to-digital

converter

(abbreviated

ADC,

A/D

or

Ato

D)

is

an

electronic

integrated

circuit

(i/c)

that

convertscontinuous

signals

to

discrete

digital

numbers.

The

reverseoperation

is

performed

by

a

digital-to-

og

converter

(DAC).CPU:Signal

processing:Average

(reduce

noise)Time

→

Frequency

(SpectrumSystem

controlUser

interfaceysis)Output

Display?numerical

or

graphical,

discrete

or

continuous,permanent

or

temporary,

visual

orauditoryHuman

factors

engineering

guidelines

andpreferred

practices

for

the

design

of

medicaldevices

(AAMI,

1993)Auxiliary

ElementsCalibration

signal

(known

voltage)control

and

feedback

(insulin

delivery)alarms

(intensive

care

monitors)transmission

of

data

to

remo ocations

(nursesstations)4

對測量系統(tǒng)的基本要求穩(wěn)定性穩(wěn)定性就是指系統(tǒng)動態(tài)過程的振蕩傾向及其恢復(fù)平衡狀態(tài)的能力。對于穩(wěn)定的系統(tǒng)，當(dāng)輸出量偏離平衡狀態(tài)時，應(yīng)能隨著時間收斂并且最后回到初始的平衡狀態(tài)。精確性一般以穩(wěn)態(tài)誤差來衡量。所謂穩(wěn)態(tài)誤差是指以一定變化規(guī)律的輸入信號作用于系統(tǒng)后，當(dāng)調(diào)整過程結(jié)束而趨于穩(wěn)定時，輸出量的實際值與期望值之間的誤差值，它反映了動態(tài)過程后期的性能。這種誤差一般是很小的?？焖傩钥焖傩允侵府?dāng)系統(tǒng)的輸出量與輸入量之間產(chǎn)生偏差時，消除這種偏差的快慢程度。快速性好的系統(tǒng)，它消除偏差的過渡過程時間就短，就能復(fù)現(xiàn)快速變化的輸入信號，因而具有較好的動態(tài)性能。安全5

Medical

measurement

constraintsMeasurement

range

are

qui ow(測量范圍窄)Most

voltages

are

in

the

micro-volt(μV)range.Low

pressures

(about

100

mm

Hg

=

1.93

psi

=13.3

kPa)Low

frequency

(from

dc

to

1

kHz)Many

crucial

variables

in

living

system

are

inaccessible

(must

bemeasured

indirectly,

ex.ECG)Inherent

variability:

Variables

measured

from

the

human

or

animalsare

seldom

deterministic.Vary

with

timeVary

among

the

patientsInterference

from

other

physiological

systemsComplex

feedbackEnergy:

X-ray,

ultrasonic

imaging,

electromagnetic,

Dopplerultrasonic

blood

flow-metersOperation:Equipment

must

be

reliable,

simple

to

operate,

and

capable

ofwithstanding

physical

abuse

and

exposure

to

corrosive

chemicals.Minimize

electric-shock

hazards6

Six

major

Trends

of

MD

TechnologyComputer-related

technology:

Robotic

SurgeryMolecular

medicine:BiochipHome-

and

self-care

products:

GlucoWatchMinimally

invasive

procedures:SwallowableCamera

PillCombination

device/drug

products:Organ

substitute

and

assist

devices:Trends

in

Medical

ElectronicsIncreasing

use

in

the

homeHigher

portability

for

sophisticated

imaging

andmonitoringUltrasoundPatient

monitors

Increasing

miniaturization

for

implantable

deviceswithvery

long

servicelivesConvergence

of

functionsWireless

and

connected

solutions

for

monitoringExplosive

growth

predicted

forChina, and

otheremerging

countries6

測控系統(tǒng)的設(shè)計自上而下（top－downapproaches):起始點是模擬電子系統(tǒng)所需求的整體性能分析，設(shè)計以集成運算放大器。自下而上（Bottom

to

up）：從基本固體物理開始，講授二極管和三極管等半導(dǎo)體器件的功能。通過實例介紹電壓放大器的三極管使用。使用三極管如何配置不同的放大器。然后，學(xué)習(xí)集成放大器。測控系統(tǒng)的設(shè)計需求分析與描述，和確定性能指標（參數(shù)確定）：被測量的量是什么？信號的大小與頻率？系統(tǒng)的測量的精度？系統(tǒng)的使用條件。及其它一些系統(tǒng)所具有的功能，如信號的顯示、記錄、功能。系統(tǒng)的成本、設(shè)計或研發(fā)的時間。工藝條件。提出和確定實現(xiàn)的方案（結(jié)構(gòu)確定）：結(jié)構(gòu)分解性能指標分配：確定前向信號通道（指從傳感器到模數(shù)轉(zhuǎn)換器的模擬信號放大、處理部分電路）所需信號放大、濾波或變換電路的級數(shù)，各級的增益，濾波器的階數(shù)、形式和截止頻率等。確定各個組成部分的具體設(shè)計。DESIGN

CRITERIASignal

factors:

sensitivity,

range,

inputimpedance,

accuracy,

linearity,

reliability,…Environment

factors:

SNR,

power,

size,

shape,stability,….Medical

factors:

invasive

or

non-invasivematerialtoxicity,

radiation,

…Economic

factors:

cost,

availability,warranty,consumable

requirements,….生物醫(yī)學(xué)測量的特點（或約束）MeasurementRangeFrequency,

HzMethodBlood

flow1

to

300

mL/s0

to

20Electromagnetic

or

ultrasonicBlood

pressure0

to

400

mmHg0

to

50Cuff

or

strain

gageCardiac

output4

to

25

L/min0

to

20Fick,

dye

dilutionElectrocardiography0.5

to

4

mV0.05

to

150Skin

electrodesElectroencephalography5

to

300

V0.5

to150Scalp

electrodesElectromyography0.1

to

5

mV0

to

10000Needle

electrodesElectroretinography0

to

900

V0

to

50Contact

lens

electrodespH3

to

13

pHunits0

to

1pH

electrodepCO240

to

100

mmHg0

to

2pCO2

electrodepO230

to

100

mmHg0

to

2pO2

electrodeP

otachography0

to

600

L/min0

to

40P

otachometerRespiratory

rate2

to

50

breaths/min0.1

to

10ImpedanceTemperature32

to

40

°C0

to

0.1Thermistor生物醫(yī)學(xué)測量的特點（或約束）SpecificationValueInputsignal

dynamic

range±5

mVDc

offset

voltage±300mVSlewrate320

mV/sFrequency

response0.05

to

150

HzInput

impedance

at

10

Hz2.5

MDclead

current0.1

Return

time

after

leadswitch1sOverload

voltage

without

damage5000VRisk

current

at

120

V10

Table Specification

values

for

an

electrocardiograph

are

agreed

uponby

a

committee.生物醫(yī)學(xué)測量的特點（或約束）與其它測量系統(tǒng)相比，生物醫(yī)學(xué)測量有以下特點：從測量值范圍上，測量的生理參數(shù)的幅值和頻率范圍都是比較低的。從測量對象上，由于測量對象是人，有生命的。被測量是動態(tài)的。許多被測生理量的很難接近。被測量是很少是確定的，測量結(jié)果是隨機的。生理數(shù)據(jù)的時間變異性和

差異性。生理系統(tǒng)間存在相互的相用，系統(tǒng)間相互聯(lián)系缺乏了解。傳感器對被測生理量的影響Simple

Instrument

ModelThe

key

functional

element

of

the

instrument

model

is

thesensor,

which

has

the

function

of

converting

theph