Reference Books and Timeline

Reference Books: Medical Instrumentation, 4th edition, J.G. Webster Advanced Engineering Mathematics (handbook) Learning with LabVIEW, Robert H. Bioshop Matlab (text book or learn from the software help)

Important Timelines: Homework Collections (20%): two weeks after the assignment Student Review Section (10%): Middle-term Exam (25%): Mar. 10, 2:00 pm Project Report (25%): May 1 Final Exam (20%): May 7, 1:00 pm

Chapter 1. Basic Concepts of Medical

Instrumentation

Walter H. Olson

Medical Instrumentation Application and

Design, 4th Edition

John G. Webster, Univ. of Wisconsin, Madison

ISBN: 978-0-471-67600-3

Chapter 1: Basic Concepts of Medical

Instrumentation

table_01_01b

fig_01_02

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 a

re two possible modifying inputs. Z1 and Z2 represent the electrode-skin i

nterface impedances.

Medical Instrumentation System

Measurand (physical quantity, property, or condition)

Sensor (convert physical measurand to electric output)

Signal conditioning (amplifier, filter, )

Output display (visual, auditory, print )

Operational Modes

direct vs. indirect (cardiac output)

sampling (temperature) vs. continuous (heart rate)

analog vs. digital

real-time vs. delayed time

Medical Measurement Constraints

Low signal (microvolt, low frequency)Noises (60 Hz)Inaccessible variables (cardiac output..)Large variations (statistical results)Low input of energy (X-ray)Easy operationSafety of patients

Classifications of Biomedical Instruments

1. Sensed quantity

pressure, flow, temperature

2. Principal of transduction

resistive, inductive, capacitive, ultrasonic

3. Organ

cardiovascular, pulmonary, nervous

4. Medical specialties

pediatric, cardiology, radiology

Biostatistics

Mean

Standard deviation

Coefficient of variation (CV)

Correlation coefficient (r)

n

xX

i

1

)( 2

n

xxs

i

%)100(

x

sCV

22 )()(

))((

yyxx

yyxxr

ii

ii

Instrument Performance:

Static Characteristics (dc or very low frequency inputs)

Accuracy:-- The difference between the true value and the

measured value divided by the true value

Precision:-- The number of distinguishable alternatives

(2.434v vs. 2.43v)

Resolution:-- Smallest incremental quantity

Reproducibility:-- The same output over some period of time

Static Characteristics (continue)

Statistical control (multiple measurements)Static sensitivityZero driftSensitivity driftLinearityInput rangeInput impedance

Static Characteristics (continue)

Figure 1.3 (a) Static-sensitivity

curve that relates desired input

xd to output y. 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 drift and

sensitivity drift can be negative.

Linearity:

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).

Input Impedance:

Power: time rate of energy transfer from the

measurement medium

),,(

),,(

FlowVelocityCurrent

pressureforceVoltage

Instrument Performance:

Dynamic Characteristics

Transfer functionsZero-order instrument: n = 0First-order instrument: n = 1Two-order instrument: n = 2

Differential/integral equations are required to relate

dynamic inputs to dynamic outputs

Differential operator: Dk dk()/dtk

Operational Transfer Function:

Frequency Transfer Function:

D can be replaced by the Laplace parameter S (j):

(Algebraic)

Dynamic CharacteristicsZero-order instrument (n = 0)

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.

Operational Transfer Function:

Frequency Transfer Function:

Based on Kirchhoffs voltage law:

y(t) = E/L [x(t)]

Dynamic CharacteristicsFirst-order instrument (n = 1)

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 large time

constants (tL) and small time constants (tS). (d) Sinusoidal frequency

response for large and

small time constants.

Frequency Transfer Function:

Operational Transfer Function:

Differential operator: Dk dk()/dtk

Advanced Engineering Mathematics (handbook)

Example 1.2 (page 30)A first-order low-pass instrument has a time constant of 20 ms. Find the maximal

sinusoidal input frequency that will keep output error due to frequency response

less than 5%. Find the phase angle at this frequency.

Example 1.3 (page 31)

From a 2 KV source in series with a 20K ohm resistor, calculate the time required

to charge a 100F defibrillator capacitor to 1.9KV.

Figure 1.7 (a) Force-

measuring spring scale, an

example of a second-order

instrument, (b) Static

sensitivity, (c) Step

response for overdamped

case z = 2, critically

damped case z = 1,

underdamped case z = 0.5.

(d) Sinusoidal steady-state

frequency response, z = 2, z

= 1, z = 0.5.

Second-order instrument (n = 2)

eq_01_25

fig_01_08

Medical

Instrument

Design

Homework

Edition 4: Problem 1.3 (page 42) Edition 3: Problem1.3 (page 39)

t)

x(t) y(t) = exp (-t/CR)

Homework

Edition 4: Problem 1.7 (page 42) Edition 3: Problem1.7 (page 41)Edition 4: Problem 1.8 (page 42) Edition 3: Problem1.8 (page 41)