Aula Teorica 1 Instrumentação Biomédica
-
Upload
api-3719280 -
Category
Documents
-
view
95 -
download
1
Transcript of Aula Teorica 1 Instrumentação Biomédica
Instrumentação BiomédicaInstrumentação Biomédica
Conceitos FundamentaisConceitos Fundamentais
JCMetrôlho, Out. 07JCMetrôlho, Out. 07
Instrumentação BiomédicaInstrumentação Biomédica 22
Biomedical engineers work in a variety of fields
•Bioinstrumentation•Biomaterials •Biomechanics•Biosignals•Biosystems•Biotransport•Cellular engineering•Clinical engineering•Tissue engineering•Rehabilitation engineering
Instrumentação BiomédicaInstrumentação Biomédica 33
Biomedical engineers work in a variety of disciplines
•Agriculture - Soil monitoring
•Botany - Measurements of metabolism
•Genetics - Human genome project
•Medicine - Anesthesiology
•Microbiology - Tissue analysis
•Pharmacology - Chemical reaction monitoring
•Veterinary science - Neutering of animals
•Zoology - Organ modeling
Instrumentação BiomédicaInstrumentação Biomédica 44
Biomedical engineers may work in a variety of environments
•IndustryIndustry
•GovernmentGovernment
•Clinical InstitutionsClinical Institutions
•AcademicResearchAcademicResearch
Instrumentação BiomédicaInstrumentação Biomédica 55
Problemstatem ent
R eviewprior work
S tatehypothesis
Performexperim ents
D esign furtherexperim ents
Analyzedata
F ina lconclusions
M oreexperim entsnecessary
Problemsolved
In the scientific method, a hypothesis is tested by experiment to determine its validity
Instrumentação BiomédicaInstrumentação Biomédica 66
C hiefcom pla int
O bta inh is tory
L is t thed ifferentia ld iagnosis
Exam inationand tests
Select furthertests
U se datato narrow the
d iagnosis
F ina ld iagnosis
M ore thanone like ly
O nly onelike ly
T reatm entand
evaluation
The physician obtains the history, examines the patient, performs tests to determine the diagnosis and prescribes treatment.
Instrumentação BiomédicaInstrumentação Biomédica 77
Sensor
D atacom m unication
D atad isp lays
E ffector
M easurand
S ignalcondition ing
S ignalprocessing
D atastorage
Feedback
O utputs
A typical measurement system uses sensors to measure the variable, has signal processing and display, and may provide feedback.
Instrumentação BiomédicaInstrumentação Biomédica 88
InstrumentPatient
InstrumentPatient
Clinician
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.
(a) (b)
Instrumentação BiomédicaInstrumentação Biomédica 99
Instrum entPatientC lin ic ian
Abnorm alreadings
In some situations, a patient may monitor vital signs and notify a clinician if abnormalities occur.
Instrumentação BiomédicaInstrumentação Biomédica 1010
MeasurementMeasurement RangeRange Frequency, HzFrequency, Hz MethodMethod
Blood flowBlood flow 1 to 300 mL/s1 to 300 mL/s 0 to 200 to 20 Electromagnetic or ultrasonicElectromagnetic or ultrasonic
Blood pressureBlood pressure 0 to 400 mmHg0 to 400 mmHg 0 to 500 to 50 Cuff or strain gageCuff or strain gage
Cardiac outputCardiac output 4 to 25 L/min4 to 25 L/min 0 to 200 to 20 Fick, dye dilutionFick, dye dilution
ElectrocardiographyElectrocardiography 0.5 to 4 mV0.5 to 4 mV 0.05 to 1500.05 to 150 Skin electrodesSkin electrodes
ElectroencephalographyElectroencephalography 5 to 300 5 to 300 VV 0.5 to 150 0.5 to 150 Scalp electrodesScalp electrodes
ElectromyographyElectromyography 0.1 to 5 mV0.1 to 5 mV 0 to 100000 to 10000 Needle electrodesNeedle electrodes
ElectroretinographyElectroretinography 0 to 900 0 to 900 V V 0 to 500 to 50 Contact lens electrodesContact lens electrodes
pHpH 3 to 13 pH units3 to 13 pH units 0 to 10 to 1 pH electrodepH electrode
ppCOCO22 40 to 100 mmHg40 to 100 mmHg 0 to 20 to 2 ppCOCO22 electrode electrode
ppOO22 30 to 100 mmHg30 to 100 mmHg 0 to 20 to 2 ppOO22 electrode electrode
PneumotachographyPneumotachography 0 to 600 L/min0 to 600 L/min 0 to 400 to 40 PneumotachometerPneumotachometer
Respiratory rateRespiratory rate 2 to 50 2 to 50 breaths/minbreaths/min 0.1 to 100.1 to 10 ImpedanceImpedance
TemperatureTemperature 32 to 40 °C32 to 40 °C 0 to 0.10 to 0.1 ThermistorThermistor
Common medical measurands
Instrumentação BiomédicaInstrumentação Biomédica 1111
SpecificationSpecification ValueValue
Pressure rangePressure range ––30 to +300 mmHg30 to +300 mmHg
Overpressure without damageOverpressure without damage ––400 to +4000 mmHg400 to +4000 mmHg
Maximum unbalanceMaximum unbalance ±75 mmHg±75 mmHg
Linearity and hysteresisLinearity and hysteresis ± 2% of reading or ± 1 mmHg± 2% of reading or ± 1 mmHg
Risk current at 120 VRisk current at 120 V 10 10 AA
Defibrillator withstandDefibrillator withstand 360 J into 50 360 J into 50
Sensor specifications for a blood pressure sensor are determined by a committee composed of individuals from academia, industry, hospitals, and government.
Instrumentação BiomédicaInstrumentação Biomédica 1212
Figure 1.1 Generalized instrumentation systemFigure 1.1 Generalized instrumentation system The sensor converts The sensor converts energy or information from the measurand to another form (usually energy or information from the measurand to another form (usually
electric). This signal is the processed and displayed so that humans can electric). This signal is the processed and displayed so that humans can perceive the information. Elements and connections shown by dashed lines perceive the information. Elements and connections shown by dashed lines
are optional for some applications.are optional for some applications.
PerceptibleoutputOutput
display
ControlAndfeedback
Signalprocessing
Datatransmission
Datastorage
VariableConversionelement
Sensor
PrimarySensingelement
Measurand
Calibrationsignal
Radiation,electric current,or other appliedenergy
Powersource
© From J. G. Webster (ed.), Medical instrumentation: application and design. 3rd ed. New York: John Wiley & Sons, 1998.
Instrumentação BiomédicaInstrumentação Biomédica 1313
Mensuranda: quantidade física, propriedade Mensuranda: quantidade física, propriedade ou condição que se pretende medirou condição que se pretende medir
biopotencialbiopotencial temperaturatemperatura impedânciaimpedância pressão, fluxopressão, fluxo concentração químicaconcentração química força, aceleração, velocidade, deslocamentoforça, aceleração, velocidade, deslocamento dimensões (imagiologia)dimensões (imagiologia)
Instrumentação BiomédicaInstrumentação Biomédica 1414
SensoresSensores Transdutor: dispositivo que converte uma Transdutor: dispositivo que converte uma
forma de energia noutra forma de energia noutra Sensor: converte uma mensuranda (valor Sensor: converte uma mensuranda (valor
de entrada) para grandeza eléctrica (valor de entrada) para grandeza eléctrica (valor de saída)de saída) responder apenas à forma de energia da responder apenas à forma de energia da
mensurandamensuranda interface com o tecido vivo, extraindo a menor interface com o tecido vivo, extraindo a menor
energia possível energia possível minimamente invasivominimamente invasivo
Instrumentação BiomédicaInstrumentação Biomédica 1515
Condicionamento de sinalCondicionamento de sinal
AmplificarAmplificar o sinal eléctrico relevante o sinal eléctrico relevante FiltrarFiltrar ruído ou outros sinais ruído ou outros sinais
indesejáveisindesejáveis LimitarLimitar amplitudes máximas amplitudes máximas AdaptarAdaptar impedâncias entre os impedâncias entre os
diferentes componentesdiferentes componentes ConverterConverter entre diferentes grandezas entre diferentes grandezas
eléctricaseléctricas
Instrumentação BiomédicaInstrumentação Biomédica 1616
VisualizaçãoVisualização
Resultado do processo de medição Resultado do processo de medição em formato adequado para fácil em formato adequado para fácil percepçãopercepção numériconumérico gráficográfico contínuo ou intermitentecontínuo ou intermitente permanente ou temporáriopermanente ou temporário visual, acústico, …visual, acústico, …
Instrumentação BiomédicaInstrumentação Biomédica 1717
Componentes auxiliaresComponentes auxiliares
sinal de calibração o mais a montante sinal de calibração o mais a montante possível na cadeia de mediçãopossível na cadeia de medição
controlo e realimentação para ajuste de controlo e realimentação para ajuste de sensor, condicionamento e visualizaçãosensor, condicionamento e visualização automático ou manualautomático ou manual
armazenamentoarmazenamento temporário ou de arquivotemporário ou de arquivo
comunicaçãocomunicação local ou remotalocal ou remota
Instrumentação BiomédicaInstrumentação Biomédica 1818
Modos de funcionamentoModos de funcionamento
directo ou indirectodirecto ou indirecto a grandeza que se pretende conhecer não está a grandeza que se pretende conhecer não está
acessívelacessível escolhe-se mensuranda com relação conhecida escolhe-se mensuranda com relação conhecida
contínuo ou por amostragemcontínuo ou por amostragem variações rápida (frequência cardiaca) ou lenta variações rápida (frequência cardiaca) ou lenta
(temperatura do corpo)(temperatura do corpo) sensoressensores
geradores: retiram energia da mensurandageradores: retiram energia da mensuranda moduladores: mensuranda controla fluxo de moduladores: mensuranda controla fluxo de
energia de fonte auxiliarenergia de fonte auxiliar
Instrumentação BiomédicaInstrumentação Biomédica 1919
Modos de funcionamentoModos de funcionamento
analógico ou digitalanalógico ou digital exactidãoexactidão repetibilidaderepetibilidade fiabilidadefiabilidade imunidade ao ruídoimunidade ao ruído processamento e visualizaçãoprocessamento e visualização
tempo real ou diferidotempo real ou diferido necessidade de processar sinal pode atrasar a necessidade de processar sinal pode atrasar a
disponibilidade dos resultadosdisponibilidade dos resultados
Instrumentação BiomédicaInstrumentação Biomédica 2020
MeasurementMeasurement RangeRange Frequency, HzFrequency, Hz MethodMethod
Blood flowBlood flow 1 to 300 mL/s1 to 300 mL/s 0 to 200 to 20 Electromagnetic or ultrasonicElectromagnetic or ultrasonic
Blood pressureBlood pressure 0 to 400 mmHg0 to 400 mmHg 0 to 500 to 50 Cuff or strain gageCuff or strain gage
Cardiac outputCardiac output 4 to 25 L/min4 to 25 L/min 0 to 200 to 20 Fick, dye dilutionFick, dye dilution
ElectrocardiographyElectrocardiography 0.5 to 4 mV0.5 to 4 mV 0.05 to 1500.05 to 150 Skin electrodesSkin electrodes
ElectroencephalographyElectroencephalography 5 to 300 5 to 300 VV 0.5 to 150 0.5 to 150 Scalp electrodesScalp electrodes
ElectromyographyElectromyography 0.1 to 5 mV0.1 to 5 mV 0 to 100000 to 10000 Needle electrodesNeedle electrodes
ElectroretinographyElectroretinography 0 to 900 0 to 900 V V 0 to 500 to 50 Contact lens electrodesContact lens electrodes
pHpH 3 to 13 pH units3 to 13 pH units 0 to 10 to 1 pH electrodepH electrode
ppCOCO22 40 to 100 mmHg40 to 100 mmHg 0 to 20 to 2 ppCOCO22 electrode electrode
ppOO22 30 to 100 mmHg30 to 100 mmHg 0 to 20 to 2 ppOO22 electrode electrode
PneumotachographyPneumotachography 0 to 600 L/min0 to 600 L/min 0 to 400 to 40 PneumotachometerPneumotachometer
Respiratory rateRespiratory rate 2 to 50 2 to 50 breaths/minbreaths/min 0.1 to 100.1 to 10 ImpedanceImpedance
TemperatureTemperature 32 to 40 °C32 to 40 °C 0 to 0.10 to 0.1 ThermistorThermistor
Table 1.1 Medical and physiological parameters.
Instrumentação BiomédicaInstrumentação Biomédica 2121
SpecificationSpecification ValueValue
Pressure rangePressure range ––30 to +300 mmHg30 to +300 mmHg
Overpressure without damageOverpressure without damage ––400 to +4000 mmHg400 to +4000 mmHg
Maximum unbalanceMaximum unbalance ±75 mmHg±75 mmHg
Linearity and hysteresisLinearity and hysteresis ± 2% of reading or ± 1 mmHg± 2% of reading or ± 1 mmHg
Risk current at 120 VRisk current at 120 V 10 10 AA
Defibrillator withstandDefibrillator withstand 360 J into 50 360 J into 50
Sensor specifications for a blood pressure sensor are determined by a committee composed of individuals from academia, industry, hospitals, and government.
Instrumentação BiomédicaInstrumentação Biomédica 2222
Figure 1.2 Simplified electrocardiographic recording systemFigure 1.2 Simplified electrocardiographic recording system Two Two possible interfering inputs are stray magnetic fields and capacitively coupled possible interfering inputs are stray magnetic fields and capacitively coupled noise. Orientation of patient cables and changes in electrode-skin impedance noise. Orientation of patient cables and changes in electrode-skin impedance
are two possible modifying inputs. are two possible modifying inputs. ZZ11 and and ZZ22 represent the electrode-skin represent the electrode-skin
interface impedances.interface impedances.
Electrodes
50-Hzac magneticfield
Displacementcurrents
Differentialamplifier
+
+Vcc
Vcc
Z1
Zbody Z2
vo
vecg
© From J. G. Webster (ed.), Medical instrumentation: application and design. 3rd ed. New York: John Wiley & Sons, 1998.
Instrumentação BiomédicaInstrumentação Biomédica 2323
Características estáticasCaracterísticas estáticas
ExactidãoExactidão PrecisãoPrecisão ResoluçãoResolução ReprodutibilidadeReprodutibilidade Controlo estatísticoControlo estatístico Sensibilidade estáticaSensibilidade estática
Instrumentação BiomédicaInstrumentação Biomédica 2424
Figure 1.3 Figure 1.3 (a) Static-sensitivity curve that relates desired input (a) Static-sensitivity curve that relates desired input xxdd to output to output
yy. Static sensitivity may be constant for only a limited range of inputs. (b) . Static sensitivity may be constant for only a limited range of inputs. (b) Static sensitivity: zero drift and sensitivity drift. Dotted lines indicate that zero Static sensitivity: zero drift and sensitivity drift. Dotted lines indicate that zero
drift and sensitivity drift can be negative. [Part (b) modified from drift and sensitivity drift can be negative. [Part (b) modified from Measurement Systems: Application and DesignMeasurement Systems: Application and Design, by E. O. Doebelin. Copyright , by E. O. Doebelin. Copyright
1990 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Co.]1990 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Co.]
Intercept b xd
y
x'd
y'
y (Output)
y = mxd + b
xd (Input)
(a)
Slope m =y
xd
Total error due to drift
Characteristic with zero and sensitivity drift
+ Zerodrift
+ Sensitivitydrift
Sensitivity drift
Zero drift
(b)
y (Output)
xd (Input)
© From J. G. Webster (ed.), Medical instrumentation: application and design. 3rd ed. New York: John Wiley & Sons, 1998.
Instrumentação BiomédicaInstrumentação Biomédica 2525
Figure 1.4 Figure 1.4 (a) Basic definition (a) Basic definition of linearity for a system or of linearity for a system or element. The same linear element. The same linear
system or element is shown system or element is shown four times for different inputs. four times for different inputs. (b) A graphical illustration of (b) A graphical illustration of
independent nonlinearity independent nonlinearity equals equals A% of the reading, or A% of the reading, or B% of full scale, whichever is B% of full scale, whichever is
greater (that is, whichever greater (that is, whichever permits the larger error). [Part permits the larger error). [Part
(b) modified from (b) modified from Measurement Measurement Systems: Application and Systems: Application and
DesignDesign, by E. O. Doebelin. , by E. O. Doebelin. Copyright Copyright 1990 by McGraw- 1990 by McGraw-Hill, Inc. Used with permission Hill, Inc. Used with permission
of McGraw-Hill Book Co.] of McGraw-Hill Book Co.] xd (Input)
B% of full scale
A% of reading
Overall tolerance band
Least-squaresstraight line
(a)
(b)
Point at whichA% of reading = B% of full scale
y (Output)
x1(x1 + y2)y1
x2Kx1 Ky1y2Linear
system
Linearsystem
Linearsystem
Linearsystem
and and
(y1 + y2)
Instrumentação BiomédicaInstrumentação Biomédica 2626
Figure 1.6 Figure 1.6 (a) A (a) A low-pass low-pass RCRC filter, an filter, an
example of a first-example of a first-order instrument. (b) order instrument. (b) Static sensitivity for Static sensitivity for constant inputs. (c) constant inputs. (c) Step response for Step response for
larger time constants larger time constants ((LL) and small time ) and small time
constants (constants (SS). (d) ). (d)
Sinusoidal frequency Sinusoidal frequency response for large response for large
and small time and small time constants.constants.
t
1
(c)
(a)
C
+
+
y(t)
Output y(t)
Input x(t)
Slope = K = 1
(b)
Y (jX (j
Logscale
1.00.707
Log scale (d)
0°
45°
90°
Log scale
t
1
0.63
LS
L
S
SL
L
S
y(t)
x(t)
x(t)
y(t)
R
Instrumentação BiomédicaInstrumentação Biomédica 2727
Figure 1.7 Figure 1.7 (a) Force-(a) Force-measuring spring measuring spring
scale, an example of a scale, an example of a second-order second-order
instrument. (b) Static instrument. (b) Static sensitivity. (c) Step sensitivity. (c) Step
response for response for overdamped case overdamped case
= 2, critically = 2, critically damped case damped case
= 1, underdamped = 1, underdamped case case = 0.5. (d) = 0.5. (d)
Sinusoidal steady-state Sinusoidal steady-state frequency response, frequency response, = 2, = 2, = 1, = 1, = 0.5. = 0.5.
[Part (a) modified from [Part (a) modified from Measurement Systems: Measurement Systems:
Application and Application and DesignDesign, by E. O. , by E. O.
Doebelin. Copyright Doebelin. Copyright 1990 by McGraw-Hill, 1990 by McGraw-Hill,
Inc. Used with Inc. Used with permission of McGraw-permission of McGraw-
Hill Book Co.]Hill Book Co.]
Outputdisplacement
Output y(t)
(b)(a)
(d)(c)
1Ks
x(t)
y(t)yn yn + 1
Resonance
2
Logscale
1
2
-90°
0.51
2 -180°
1
0.5
0.5
Log scale
Log scale
K1
t
t
Input x(t)
Slope K =1
Ks
InputForce x(t)
0
0°
n
n
Y (jX (j
y(t)
Instrumentação BiomédicaInstrumentação Biomédica 2828
Figure 1.8 Design Figure 1.8 Design process for medical process for medical
instruments instruments Choice and Choice and design of instruments are design of instruments are affected by signal factors, affected by signal factors,
and also by environmental, and also by environmental, medical, and economic medical, and economic factors. (Revised from factors. (Revised from
Transducers for Biomedical Transducers for Biomedical Measurements: Application Measurements: Application
and Design, and Design, by R. S. C. by R. S. C. Cobbold. Copyright Cobbold. Copyright 1974, 1974,
John Wiley and Sons, Inc. John Wiley and Sons, Inc. Used by permission of John Used by permission of John
Wiley and Sons, Inc.)Wiley and Sons, Inc.)