致于欣立-2生物医学电子学

医

学20生13物－2医01学4学电年子第学一学期生物医学乔清理2013,08,28主要内容电测量的优点生物医学测量系统的一般结构生物医学测量的特点（或约束）对测量系统的基本要求生物医学测量趋势测控系统的设计1.测量的概念与分类获取传输处理控制…信息获取是了解信息流组成，

疾病重要的的一环。测量的定义测量是为确定被测对象的量值而进行的实验过程。测量结果＝测量数值*测量单位即：X=X0

*{X}广义测量的定义广义地讲，测量不仅对被测的物理量进行定量的测量，而且还包括对更广泛的被测对象进行定性、定位的测量。而测量结果也不仅仅是由量值和单位来表征的一维信息，还可以用二维或 的图形、图像来显示被测对象的属性特征、空间分布、 结构等。根据所测量的参数，测量分为电量测量和非电量测量电量测量：心电信号，直接由电极拾取；非电量测量：血压、体温、呼氧等都需要通过各种传感器拾取，然后转换为与之有确定函数关系的电信号测量的分类2.电测法的优点具有极精细的分辨力和很宽的测量范围。采取电子技术，可以很方便地改变仪器的灵敏度和测量范围。电子测量仪器具有极小的惯性。既能测量变化缓慢的量，又可测量快速变化的量。有利于信息传递。无论在时间上还是在空间上可以很方便地实现遥测。灵活的变化技术和各种运算和处理、显示和记录。。PerceptibleoutputOutputdisplayControlAndfeedbackCPUDatatransmissionDatastorageSignalConditiongSensorMeasurandRadiation,electric

current,or

otherappliedenergyCalibrationsignalPowersource3生物医学测量系统的构成原理框图A/D生物医学测量系统的构成传感器：非电量到电量的变换；

信号调理电路：阻抗变换，放大，滤除噪声，抗混频；动态范围匹配A/D转换：微处理器：信号处理，系统控制D/A转换：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生物医学测量系统的构成原理框图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

对测量系统的基本要求稳定性稳定性就是指系统动态过程的振荡倾向及其恢复平衡状态的能力。对于稳定的系统，当输出量偏离平衡状态时，应能随着时间收敛并且最后回到初始的平衡状态。精确性一般以稳态误差来衡量。所谓稳态误差是指以一定变化规律的输入信号作用于系统后，当调整过程结束而趋于稳定时，输出量的实际值与期望值之间的误差值，它反映了动态过程后期的性能。这种误差一般是很小的。快速性快速性是指当系统的输出量与输入量之间产生偏差时，消除这种偏差的快慢程度。快速性好的系统，它消除偏差的过渡过程时间就短，就能复现快速变化的输入信号，因而具有较好的动态性能。安全5

Medical

measurement

constraintsMeasurement

range

are

qui ow(测量范围窄)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

测控系统的设计自上而下（top－downapproaches):起始点是模拟电子系统所需求的整体性能分析，设计以集成运算放大器。自下而上（Bottom

to

up）：从基本固体物理开始，讲授二极管和三极管等半导体器件的功能。通过实例介绍电压放大器的三极管使用。使用三极管如何配置不同的放大器。然后，学习集成放大器。测控系统的设计需求分析与描述，和确定性能指标（参数确定）：被测量的量是什么？信号的大小与频率？系统的测量的精度？系统的使用条件。及其它一些系统所具有的功能，如信号的显示、记录、功能。系统的成本、设计或研发的时间。工艺条件。提出和确定实现的方案（结构确定）：结构分解性能指标分配：确定前向信号通道（指从传感器到模数转换器的模拟信号放大、处理部分电路）所需信号放大、滤波或变换电路的级数，各级的增益，滤波器的阶数、形式和截止频率等。确定各个组成部分的具体设计。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,….生物医学测量的特点（或约束）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生物医学测量的特点（或约束）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.生物医学测量的特点（或约束）与其它测量系统相比，生物医学测量有以下特点：从测量值范围上，测量的生理参数的幅值和频率范围都是比较低的。从测量对象上，由于测量对象是人，有生命的。被测量是动态的。许多被测生理量的很难接近。被测量是很少是确定的，测量结果是随机的。生理数据的时间变异性和

差异性。生理系统间存在相互的相用，系统间相互联系缺乏了解。传感器对被测生理量的影响Simple

Instrument

ModelThe

key

functional

element

of

the

instrument

model

is

thesensor,

which

has

the

function

of

converting

theph