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BM 402 ENGINEERING IN MEDICINE LECTURE NOTES Ata AKIN Institute of Biomedical Engineering Boğaziçi University © 2009 by Ata Akın

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Page 1: BM 402 Lecture Notes p23

BM 402

ENGINEERING IN MEDICINE LECTURE NOTES

Ata AKIN

Institute of Biomedical Engineering Boğaziçi University

© 2009 by Ata Akın

Page 2: BM 402 Lecture Notes p23

1

Biomedical Engineering

“Health care delivery team” that seeks new (innovative) solutions for the difficult problems

confronting modern society

Innovation patent:

1. Novel no one should have taught about these before

2. Non-(not) obvious

3. Applicable must serve a new purpose

History of Medicine

Primitive medicine (BC 10,000)

They did not have any medication but they were interested in:

Art of herb doctoring

Bone setting

Midwifery

Surgery

They believed that diseases are visitations of evil spirits.

Egyptians (BC 3,000)

Imhotep (peaceful sleep), the architect of the 1st pyramid

Page 3: BM 402 Lecture Notes p23

2

Greek Medicine (BC 500)

God of healing: Aesculapius

Hospitals with tempts

Island of Cos: Hippocrates

o Injected “scientific spirit” into medicine.

Scientific spirit: systematic approach (cause ↔ effect), observation

o He was able to bring diagnostic observation clinical treatment

Romans (AD 500)

To use proper sewer system (public health)

Refrigerated foods (sterile and fresh)

First aid (they were warriors)

Dark Ages

Church dominates medicine

Belief in drugs meant distrust to the healing power of pray

Renaissance (AD 1,500)

Anatomical investigations

Leonardo daVinci Golden Ratio

Florence Nightingale (19th century) (English Nurse)

Hospital conditions accounted more than the diseases in death amounts

She discovered the importance of nursing

Page 4: BM 402 Lecture Notes p23

3

1896 Wilhelm Conrad Roentgen discovered X-ray

1901 He won the Nobel Prize

1906 Siemens & General Electric made the first X-ray machine

1914 X-ray machine became mobile and it could work without electric.

1903 Electrocardiogram (ECG)

Biomedical Engineering

Diagnostic Systems

- Medical Instrumentation

- Signal / Image Processing

- Nanomedicine

Therapeutic Systems

- Instrumentation

- Prosthetic devices

- Rehabilitation

Clinical Engineering Medical Informatics Biotechnology

- Biosensors

Page 5: BM 402 Lecture Notes p23

4

PHYSIOLOGY & ANATOMY (REVIEW)

Physiological Systems

A group of interconnected or independent organs that work together to perform a specific

function or a group of functions in the body

System (Transfer) Function

System: processes inputs to produce outputs

HW 1

PART I: Find 2 different definitions of Biomedical Engineering

PART II: Find websites related to Biomedical Engineering and organize them under the

following headings:

1. Academic Websites

2. Industry

3. Professional Organizations

h (t) x (t) y (t)

Physiological System

Biochemical

Physical

Electrical

Environmental

INPUTS

Biochemical

Physical

Electrical

OUTPUTS

Page 6: BM 402 Lecture Notes p23

5

Lung

Body

SA node

AV node

Circulatory (Cardiovascular) System

Organs: heart, blood vessels

Left Ventricle: Responsible for pumping oxygen rich blood to the body

The heart works with electricity.

Left Atrium

Left Ventricle

Aorta

Page 7: BM 402 Lecture Notes p23

6

SA node has a direct contact from central nervous system to control / modulate the rhythm of

the heart.

Heart rate modulators:

1. Central nervous system

2. Hormonal stimulation

3. Blood flow (mechanical)

4. Biochemical / ionic modulations on a heart muscle

Coronary arteries supply oxygen, glucose, blood to the tissue of the heart.

No blood supply due to obstruction occlusion ischemia hypoxia cell death

Ectopic focus ventricular fibrillation

Page 8: BM 402 Lecture Notes p23

7

Nervous System

Integration and control of all body functions

Stroke: Bleeding of blood vessels resulting in partial paralysis

Blood Vessels

Central Nervous System (CNS)

- All the nerve tissue enclosed by the bone

- Brain & spinal cord

Peripheral Nervous System (PNS)

- Nerve tissue that is not enclosed by the bone

- Nerve fibers from the spinal cord, muscle

nerve fibers

Page 9: BM 402 Lecture Notes p23

8

Coagulant fills where there’s an explosion

Fibers cross over in brain stem, left side of the brain controls the right side of the body.

Frontal executive function

Parietal motor-sensory systems

Temporal auditory

Occipital vision

Page 10: BM 402 Lecture Notes p23

9

Reflex Arch

There are multiple control systems in the brain

Split brain syndrome (still used to treat epilepsy)

Underneath the frontal lobe emotional control and memory

Corpus Callosum

Bridge to share information

Page 11: BM 402 Lecture Notes p23

10

Cerebrospinal fluid underneath and around the brain

The top and under pressures are the same

The fluid is inside 4 ventricular chambers

Page 12: BM 402 Lecture Notes p23

11

Respiratory (Pulmonary) System

Enables cardiovascular system to exchange gases with air

Nose, pharynx, larynx, trachea, lungs

lunglungairair VPVP =

Pair Vair is constant Plung decreases, Vlung increases rush of fresh air through the lungs

Huge oxygen gradient between the deoxygenated blood and alveolar

As the red blood cell flows, oxygen is diffused through mucosa (secreted by the certain cells

that have hair) and the red blood cell fills with oxygen. CO2 is formed as HCO3- because it is

not desired in gas phase in the plasma. It is dissolved in acid form. The undissolved part is

carried by the red blood cell.

CO2 is diffused freely in alveolar.

Page 13: BM 402 Lecture Notes p23

12

Smoking: Smoke has tar in it. Tar sits on top of mucosal layer. Alveolar needs to secrete

more mucosa. The thickness has increased, diffusion takes longer. If you smoke more, the

distance that the oxygen should travel increases and there’s no more oxygen transfer.

Emphysema

Respiratory system is controlled by signals if cerebellum.

Gastrointestinal (Digestive) System

Concerned with the ingestion and digestion of food, elimination of the residues of the

gastrointestinal system

Liver, gallbladder, pancreas, stomach, intestines colon

Esophagus peristaltic activity

(Squeezes the food down)

Page 14: BM 402 Lecture Notes p23

13

Gastroesophageal reflux

1. Neoplasia

2. Dysplasia

3. Cancerous formation

o Immortality

o Uncontrolled growth

Metastate

Barnett’s Esophagus

Urogenital System

Production, storage, elimination of urine

Reproduction

o Kidneys, bladder, ovaries, prostate

Kidneys: Responsible for maintaining water equilibrium, balance of minerals, and removal of

toxic components from the blood.

Filtration system, continuous blood flow

Page 15: BM 402 Lecture Notes p23

14

Kidneys maintain mineral level (Ca, Mg, Zn, Fe)

maintain homeostasis (static state of the body)

Kidneys are responsible for maintaining blood pressure.

Too much water pressure in blood vessels

Kidneys send hormones to blood vessels to relax the vessels renin activates angiotensin

Squeezing down the vessels

Input: Blood Output: Blood

Bladder

Page 16: BM 402 Lecture Notes p23

15

Central Nervous System

Autonomic Nervous System

Dialysis: A filtration system to remove toxins and urea from the blood.

Kidney Stone:

Pancreas: Responsible for secreting hormones to maintain blood glucose level.

Hypoglycemia

Diabetes Mellitus

Sympathetic Nervous System

Fight Mode!

- Excitatory

Parasympathetic Nervous System

Flight Mode!

Page 17: BM 402 Lecture Notes p23

16

Musculoskeletal System

Muscles & skeleton

Maintaining balance, movement, keeping warm

Amount of signals determine how many muscles should be recruited to carry the weight.

Signals can be sent as a whole or one by one.

Page 18: BM 402 Lecture Notes p23

17

Force generated by muscles is a function of

Neuronal stimulation from the brain (frequency & intensity)

Amount of blood supply

Available nutrients

Ionic concentration around muscle (Ca2+)

Previous activity level

Lactic acid vs. endurance

Hypertrophy

Endocrine System

Regulation and control of visceral functions

Secretes hormones via glands that control growth, metabolism and reproduction.

o Pituitary gland, thyroid, parathyroid, adrenalin gland, thymus

Glands are bags that are covered by muscles.

Page 19: BM 402 Lecture Notes p23

18

Pituitary gland: growth, reproduction

Thyroid gland: around the trachea at the larynx

Controls the rate of metabolism

o Hyperthyroidism

o Hypothyroidism

Parathyroid gland: on top (around) the thyroid gland

Responsible for maintaining calcium balance in the blood stream and tissues

Adrenal glands epinephrine

• Small amounts vasodilation

• Large amounts vasoconstriction

Page 20: BM 402 Lecture Notes p23

19

Hematopoietic System & Lymphatic System

Production of blood & blood components

Immune system components

Bone marrow, spleen, lymphatic tissues

Bone marrow: production of red & white blood cells

Spleen: storage of blood cells

Lymphatic tissues: collection of plasma, dead red blood cells

Production of immune system components

Red blood cells: storage of hemoglobin

White blood cells: soldiers of the body

Integumental System

Skin, hair, nails

Skin protection

Nails finger support

Hair protects the brain from heating, provides sweating

HW 2

PART I: Pick a physiological system of your choice and describe its functions, organs in 2

pages

Page 21: BM 402 Lecture Notes p23

20

PART II: Find a major disease of this system. Explain its pathophysiology, progression,

diagnosis and therapeutic interventions in 1 page.

Page 22: BM 402 Lecture Notes p23

21

BIOMEDICAL SENSORS

Sensors that are used to measure electrical, chemical, physical activities from human body

Invasive

Ionization (radiation) X-ray, UV, γ-ray

Contact with blood

Intrusion into the body

Minimally invasive

Contact with blood

Intrusion into the body

Non-invasive

Surface or remote diagnosis / therapy

Biomedical Instruments

Diagnostic Therapeutic

Invasiveness

Non-invasive Minimally invasive

Invasive

Page 23: BM 402 Lecture Notes p23

22

Biomedical Instruments

A General Block Diagram for a Diagnostic Instrument

BIOMEDICAL SENSORS

Chemical Sensors

Blood components, glucose, ions, hormones, pH, O2, CO2

Clark Electrode

Rate of electron transfer is measured by the resistance of electrodes.

ALR

sLawOhmIRVρ

=

= '

O2 measurement

Clark Electrode

- Invasive (accurate)

- Non-invasive (not so accurate)

Pulse Oximetry

- Non-invasive (not so accurate)

Page 24: BM 402 Lecture Notes p23

23

↓→+

+↔

→++

−+

−+

−−

AgClClAgeAgAg

OHeOHO 4422

Pulse Oximetry

Hb

HbO2

Finger

Detector: non-laser red light sources

Light is used to measure the concentrations of [HbO2] and [Hb]

(Near infrared)

( )( )⎥⎦

⎤⎢⎣

⎡−=

2

12 λ

λODOD

BAOS

S O2: Saturation of O2

OD: Optical Density

Offline Sensors

Glucose, hormone, blood components

O2 measurement: spirometer to measure O2 gas amount and CO2 gas in the air

exchanged by the lungs

Detector

λ1 λ2

Page 25: BM 402 Lecture Notes p23

24

Electrical Measurements

Results of biopotentials biologically generated electrical signals

Cells are electrically excitable.

Resting membrane potential

Due to the existence of ions across the cell

membrane

Action Potential

is due to the rapid exchange of ions

across cell membrane through channels

and gates

muscle cell gates

heart muscle gap junctions transfer electrical potentials between cells

Dipole

Einthoven’s triangle

Page 26: BM 402 Lecture Notes p23

25

Electrocardiogram (ECG)

P: atrial contraction

QRS: left ventricle contraction

T: refilling of the ventricle

Heart Rate

Pacemaker

Electrolyte: electrically conductive gel with NaCl

Electrical Sensors

Non-invasive

Surface type Surface electrodes

Invasive

Needle deep tissue measurement

Skin

Electrolyte

Wire

Double side adhesive

Ag / AgCl

Page 27: BM 402 Lecture Notes p23

26

It allows the passage of electrical signals to the metal

Adhesive secures the electrode onto the skin surface.

Electromyogram (EMG)

Measurement of electrical signals of the muscle

Needle electrodes

200-400 µm thick wires

Invasive

Electroencelophalogram (EEG)

The electrodes make a goof approximation about the electrical

activity.

Cable of electricity

Stimulus

+_

_ +

Page 28: BM 402 Lecture Notes p23

27

20 electrodes across the head (cap electrodes)

Visual Evoked Potential

Evoked Response

Cortical electrodes

HW 3

PART I: What are the operational principles and clinical applications of

1. ECG

2. EMG

3. EEG (1 page each)

PART II: What is functional electrical stimulation (FES)? What are its clinical applications?

(1 page)

Physical Measurements

Volume, force, temperature, pressure, sound

Volume Measurement

A

+

Rubber strand

Breath

Page 29: BM 402 Lecture Notes p23

28

To measure the change in current:

ALR

IVR

ρ=

=

Calibration curve

Transducer

Breathing by rubber strand:

lRR∆∝∆

∝ρ

I II III

Linear sensitivity

I limit of detection

II linear range

III saturation (cut-off) range

∆V

T period min

breathsofnoRateBreath =

12-15 min-1

- Amplitude gives basic info about the amount of air exchange

Page 30: BM 402 Lecture Notes p23

29

Force & Strain Measurement

lRF ∆∝∆∝

1. Intraesophageal balloon

2. Radiofloroscopy

A

+V

I

l Rubber substrate

∆l

F

Pump

Page 31: BM 402 Lecture Notes p23

30

o Ingest a liquid absorber of X-ray

3. Strain Gage

3 of these techniques are not accurate.

4. Piezoelectric Transducer

o Force, pressure, flow

A crystal that produces electricity when mechanically strained.

Rubber

Needle Surface of stomach

Metal

Voltmeter F F

Page 32: BM 402 Lecture Notes p23

31

Q: electric charge produced F: force applied

k: coefficient of the crystal

Blood Pressure Measurement

Temperature Measurement

1. Mercury Based Measurement

2. Electrical Thermometer

3. Optical Thermometer

Electrical Thermometer

kFQ =

+

I Thermistor

Page 33: BM 402 Lecture Notes p23

32

Biosensors (≠ medical sensors)

Sensors that measure the concentration of chemical components of solution

Glucose + enzyme → glucanic acid → alters the pH of the sheet

pH Glucose

HW 4

PART I: What is a biosensor? Find 1 clinical application for it.

PART II: What is a molecular beacon? What is a quantum dot? Find their usage in biology.

⎥⎦

⎤⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛−=

00

11exp)(TT

RTR β

TRI 1∝∆∝∆

Cholesterol

Glucose Membrane

Biological compound

Transducer Enzyme

Page 34: BM 402 Lecture Notes p23

33

BIOMEDICAL INSTRUMENTATION

A generalized block diagram of a biomedical device

Data Processing Unit

Noise Removal

Elimination of unwanted signals

Electromagnetic interference

= powerlines, TV-Radio broadcast, mobile phones, computers, lab equipment

Page 35: BM 402 Lecture Notes p23

34

1. Noise filter

Transfer function filter out unwanted noise

2. Data Filter

Designed to extract relevant physiological information out of others

Low pass filter, high pass filter, band pass filter

Convolution: y(t) = x(t) * hD(t)

3. Gain

Performed to increase the amplitude of the signal

h (t)

y (t) x (t)

Transfer Function

hD (t)

y (t) x (t)

x (t) G y (t) = G · x (t)

Page 36: BM 402 Lecture Notes p23

35

4. Differential Measurement

)()()(

)()()()()()(

21

2

1

tVtVVVtV

tntVtVtntVtV

LRo

L

R

−=−=

+=−+=

To eliminate “common” noise

Typical signal conditional steps

V1(t)

V2(t) VR(t)

VL(t)

n(t)

+

_Vo(t)

Differential measure

Noise filter

Data filter

Gain

G y (t) +

_ hN (t) hD (t)

[ ])()( 21 txtx − [ ] )()()( 21 thtxtx N∗− [ ] )()()()( 21 ththtxtx DN ∗∗−

[ ] )()()()()( 21 ththtxtxGty DN ∗∗−=

Sensor SCU CPU

CPU = Microprocessor A/D converter +

Page 37: BM 402 Lecture Notes p23

36

Analog to Digital Convertors

Types of Signals

1. Analog real world, continuous signal

2. Digital digitized signals sampled and stored in the computer

o A digital representation of the signal

A / D Converter

Resolutions

1. Temporary Resolution

o How fast a signal is sampled [samples/sec] = sampling rate Fs

Typically Fs = 1000 samples/sec

2. Dynamic Resolution

o How fine are you quantizing a signal? [bits]

n

VVlevelsofno

RangeDynamic2

minmax −==λ

n: number of bits = 10-12 bits

Ex: 12 bit A / D converter, Fs = 200 samples/sec records data for 10 min from 16 electrodes.

What is the size of the data file?

( ) MBytesbitsM

sensorsofnorecordofDurationFbitsofnosizeData s

8.22316601020012 ≈=××××=

×××=

Page 38: BM 402 Lecture Notes p23

Bioelec

Biomag

Biochem

Biomec

Bioacus

ctric Signals

Generated b

Result o

gnetic Signa

Magnetic fi

Transcr

Electric

mical Signa

concentrati

gases

chanical Sig

motion, dis

stic Signals

due to vibra

s

by nerve an

of electroche

als

fields are ge

ranial Magn

cal convulsi

als

ons of ions

gnals

splacement,

ation, flow

Biomedic

nd muscle ti

emical chan

nerated due

netic Stimul

ion therapy

(Ca2+, K+,

tension, for

of blood, re

cal Signal P

ssues when

nges across

e to changes

Ma

lator

Na+, Cl-…)

rce, pressur

espiratory sy

Processing

n they are el

the cell mem

s in electric

agnetoencep

), hormones

re, flow

ystem (lung

ectrically ac

mbrane.

field.

phalogram (

s, chemical

g) sounds

ctive.

(MEG)

compound

37

s, blood

Page 39: BM 402 Lecture Notes p23

38

Deterministic: an explicit mathematical representation exists

periodic signals )()( Ttxtx +=

aperiodic signals TtAetx /)( −=

Characteristics of Signals

Deterministic Signals

Periodic Aperiodic

Random (stochastic) Signals

x(t)

t

T

A -

Tte /−

t

x(t)

Page 40: BM 402 Lecture Notes p23

39

Random: characterized by statistical values (mean, standard deviation)

EEG signals

Fourier Transform

A means of representing the contribution (weight) of different frequencies within a signal

1. )sin()( 111 tAtx ω=

2. )sin()( 222 tAtx ω=

A1

- A1

T1

A2

-A2

T2

11 2 fπω = HzT

f 121

11 ==

22 2 fπω = HzT

f 251

22 ==

12

21

21

AATTff

<><

xT(t)

∫∞

∞−

−= dtetxfx tjω)()(

∫∞

∞−

−= ωπ

ω defxtx tj)(21)(

Page 41: BM 402 Lecture Notes p23

40

Fourier Transform is random.

EEG

o Grand averaging – Ensemble overgoing

A1

A2

x(f)

frequency f1 f2

Data Compression

Page 42: BM 402 Lecture Notes p23

41

Quality in Medical Imaging

1. Spatial Resolution

How small can we detect [pixels/area]

2. Contrast Resolution

How fine of colors do we see? [bits/pixel]

3. Temporal Resolution

How many images can you take in 1 second?

[frame rate] = [frames / second] ≥ 24 frames/sec (real time)

Medical Imaging

Functionality

Morphological

Anatomical

Map of organs

Physiological

Provide information

on how well an organ

is functioning

Invasiveness

Non-invasive

Remote

Surface contact

Min-invasive

Intrusion into the

body

Contact w/ blood

Invasive

Radiation

Page 43: BM 402 Lecture Notes p23

42

Radiation Imaging

- Depends on the use of X-rays to image the absorption (attenuation) distribution of the

tissues

I < I0

1896 – Discovery of X-ray

1901 – The very first Nobel Prize was given to Wilhelm Conrad Roentgen

Object

I0 I

Photographic film covered with

fluorescent material

Source

Object

Fluorescent material

Visible light

Page 44: BM 402 Lecture Notes p23

43

Principles of X-Ray Imaging

Attenuation of X-rays by tissues between body parts having minimally different density, fat,

muscle, result in a shadow image

Collimator: aligns X-ray beam

Ω

e-

X-ray lamp

Pulse generation

Collimator

Florescent cover

Photographic film

A grid of photo detector

Holes

Pb

Page 45: BM 402 Lecture Notes p23

44

Physics of X-Ray Imaging

hfE =

h: Planck’s constant

f: frequency of electromagnetic wave

↓=↑λcf

Ionization: decomposition of matter

- Vaporization of tissues

γ rays, X rays pass through tissues and give permanent damage to skin

Ionizing radiation

z

I0

Detector X-ray source

Page 46: BM 402 Lecture Notes p23

45

mzeIzI ρ−= 0)(

z: distance between source and detector

ρ: density of the object

µ: attenuation coefficient

Units of X-ray Exposure

Roentgen R = 2.58 * 10-14 C/kg

- Produces ionization of either charge (+ or -)

When light enters (I0), some of it is absorbed by the body not to eliminate X-ray

immediately.

A typical X-ray session: 10 – 100 millirads

- Absorption of X-ray by body (chest X-ray)

Onset of radiative effect: 50 rads

Radiation death > 200 rads

Geometric Unsharpness

X-ray source

Fan beam

f

Image plane

s

t

Page 47: BM 402 Lecture Notes p23

46

s: source to image plane distance

t: center of object to image plane distance

f: fixed size of the object

tstfd

−⋅

=

Goal: minimize d (f fixed)

1. Increase s increase source – detector distance

2. Decrease t bring the object close to image plane

X-rays planar image

Computer Aide Tomography Scanner (CAT Scan)

- Computerized Tomography (CT)

The detector rotates and cross-section images are obtained at every 1-2o

Source

Detector

Page 48: BM 402 Lecture Notes p23

47

iii µρα =

We have 4 unknowns

We need 4 independent projections to solve ’s

Back Projection Algorithm

- Reconstruct cross-sectional image of an object by projected data

1st Generation CT

1 source, 1 detector

60 seconds to 4-5 minutes for each rotation

Rotates at every 6o angle for one cross-section

2nd Generation CT

1 source 30 detectors

All detectors are close to the source at equal distances to reduce geometrical sharpness

3rd Generation CT

1

ρ1 µ1

2

ρ2 µ2

3

ρ3 µ3

4

ρ4 µ4

1+3

1+2

1+4

2+4

Page 49: BM 402 Lecture Notes p23

48

300 detectors 2 – 4 seconds

4th Generation CT

Only the source (fan beam) is rotating

700 detectors around (2 – 4 seconds)

Fluoroscopy

Patient is given a radio opaque (X-ray absorber) material and the movement of this material

is observed under light by camera.

Angiography

Injection of radio opaque material into the veins for observation of occlusions

HW 5

1. What is X-ray mammography?

2. What is balloon angioplasty?

Page 50: BM 402 Lecture Notes p23

49

Radionuclide Imaging

Nuclear medicine radioactive elements

Invasive ionizing radiation

Functional physiological imaging Curries

Nuclear particles

energyenp

energyepn

e

e

+++→

+++→−++

−−+

υ

υ

The solution circulates in the body and targets several organs

I radioisotope mixed in the solution and accumulates in thyroid

C6H12O6 Isotopes C11, C15 accumulates in the parts where glucose is consumed

e-

n, p+

energy

Powder

radioactive mix in

solution

Through a catheter

Page 51: BM 402 Lecture Notes p23

50

Positron Emission Tomography (PET Scan)

An imaging technique that uses γ cameras ( cameras) to monitor the whereabouts and

intensity of a radioactive element injected into the body

It is possible to monitor the progress of the activity in

time.

It can be used to measure the effect of chemotherapy.

It can also be used to measure the effect of the drugs..

Radioactive Decay

teNtN λ−= 0)(

N0: initial amount of material

λ: decay constant

t: time

λ693.0

2/1 =T

Page 52: BM 402 Lecture Notes p23

51

Biological Half-life

Time needed for the body to excrete half of the amount of radionuclide. Tb1/2

b

beff

TTTT

T2/12/1

2/12/12/1 +

×=

O15, T1/2 = 122 sec

C11, T1/2 = 20.5 min

Molecular Beacon

Quantum Dot

Page 53: BM 402 Lecture Notes p23

52

Magnetic Resonance Imaging (MRI)

- Uses non-ionizing radiation to probe the soft tissue contrast

- Provides excellent soft tissue contrast

Physics of MRI

Uses electromagnetic waves at radiofrequency (50-60 MHz)

Charged electron spinning around the axis

- Creation of 2 poles

- Magnetic dipole moment

Magnet

1. All spinning nuclei have a characteristic resonance frequency which depends on the

atomic composition

2. When atoms are combined to form larger molecules, their overall resonance frequency

depends on their total weight

Non-magnetic

- Because all moments facing different directions

S N

All moments are at the same direction

Page 54: BM 402 Lecture Notes p23

53

Nuclear Magnetic Resistance Spectroscopy (NMRS)

Larmor Frequency

fπωβγω

20

==

γ: gyromagnetic ratio

0: applied magnetic field

Each molecule starts to rotate according to gyromagnetic ratio, resulting in ωA, ωB, ωC, ωD.

DCBAT

T

A

IIIIIII

A

+++=

×∝ 100%

Different proportion of molecules

Different spinning frequency

Page 55: BM 402 Lecture Notes p23

54

PG Re

B1

B0

S N

1. Place the sample inside a static magnetic field (B0)

2. Close S1 (off S2)

Generate a B1 B0, B1 << B0 at a specific “ω0”

3. Off S1, on S2

Listen to incoming signal

Free Induction Decay which is a signal like this:

A the amount of compound present within the sample

τ the density of compound present within the sample

PG: Pulse Generator

Re: Receiver

FID

τ A

Page 56: BM 402 Lecture Notes p23

55

Imaging Takes Place In MR

Idea: Image 3-D object according to the distribution of H+ ion

Each cube is called a voxel.

Min resolution: 1 mm x 1 mm x 1 mm

↑=↑

→ ++

TT

H

B

H

ω

γ

Rec PC

PGX

S

PGY

PGZ

Srec

Display

SX SY

SZ

N

Page 57: BM 402 Lecture Notes p23

56

PG require high current to operate

High current means heat generation cooling system is necessary

MRI

- An anatomical imaging technique

- Used in observing tissue contrast changes

(Inflammations, lesions, tumor formation, muscle injury)

- Contrast agents enhances MR signal to investigate joints (Gd injection)

Functional MRI (fMRI)

- Used only for research

- Measurement of physiological changes in human body

(Manic depressive – normal brain)

It uses hemoglobin molecule to trace the functional activity level of the brain.

HW 6

PART I: What is CT-PET Scanner? What is its clinical use?

PART II: What is functional MRI and its clinical use?

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57

ULTRASOUND IMAGING

Uses sound waves to probe the mechanical properties of the tissues (pressure waves)

= 1500 m/sec

Some sound waves reflect from the boundary. Some continue their way.

“ultra” not audible ≈ 5 – 30 MHz

ff zfat ePzP α−= 0)(

P0: initial intensity of pressure wave

f: attenuation coefficient of the tissue

f = 0f f: frequency of operation

0: initial coefficient

zf: thickness of the tissue

f ↑ Pf ↓ (more attenuation) less penetration depth but spatial resolution increases

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Amplit

Brightn

tude (A – m

ness Mode

Anat

mode) Ultra

(B Mode)

Dia

tomical

Med

asound

agnostic

Funct

Blood

dical Ultras

ional

d flow

ound

Therapeut

- Ki

- W

- Bo

- Mu

- Su

tic

idney stones

ound healin

one healing

uscle injury

urgical

s (lithotripsy

ng

y rehab

58

y)

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59

Doppler Ultrasound

Doppler Effect is the result of changing the wavelength of a source by its velocity.

Array of US sensors

The echoes are turned into gray scale image

Non-invasive!

P1 (fd)

P0 θ

US Beam

f0

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60

0cos2 fC

fdθϑ

=

: velocity of object

C: speed of sound

Kidney Imaging

Occlusion Front (coronal) view

f0

fd : measure the change in blood velocity

Blood moving away from the probe

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61

Echocardiogram

B – mode: observe anatomical problems

Doppler: quantify the degree of disease

Doppler is less invasive than B – mode because the patient is exposed to less Ultrasound.

(Still the two applications are non-invasive)

Blood towards the probe

Kidney stone

B – Mode + Doppler US

Live anatomical image of the heart

+ Movement of blood through the heart

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Therapeutic Ultrasound

Lithotripsy (stone breaking)

Locating the Stone

Bathtub

Ultrasound (transmitter)

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Electro Shock Wave Lithotripsy

Biomedical Optics

The use of light in diagnostic and therapeutic applications

Diagnostic

Microscopic

(<100µm)

Macroscopic

(>100µm)

Therapeutic

Surgical Rehab Cosmetic

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64

Light and Matter Interaction

Depends on the

1. Wavelength

2. Intensity

Visible Light Imaging

- Endoscopy

- Coils to move the tubes to look around the organs

- 4 holes, 5 mm in dimension

Fluorescence Imaging

- A certain color of light is used to excite certain chromophores

Absorption Scattering

γ ray X ray UV vis Infrared

Non-invasive

(Diagnostic)

High water absorption

Invasive

(Treat cancer)

Less water absorption

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65

Therapy

Surgical inventions

o Cut the tissues

o Coagulate the vessels and tissues

o Ablate the vessels and tissues

o Weld the tissues

Laser

Coherent, focused light beam

Rehabilitation Procedures of Light

Infrared Therapy

o Tissue Damage

Cosmetic applications

1. Plastic Surgery

2. Epilation

Pupil

Cornea

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66

Rehabilitation Engineering

Application of technology to help (ease) the problems faced by people with disabilities

Activities in Rehabilitation Engineering

1. Prosthetics and Orthotics

Artificial hand, wrist, arms, foot, legs,

Hand splits, upper limb braces

Bone / joint prosthetics

- Functional

- Biocompatible

2. Assistive Devices for persons with severe visual impairments

- Devices to aid reading, writing

TV magnifiers, electronic Braille

- Aids for independent mobility (laser cane)

3. Assistive Devices for persons with severe auditory impairments

- Digital hearing aids cochlear implant

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- Lip reading instruments

4. Mobility manipulation aids

- Grabbers, feeders, page turners, wheel chairs, driving aids

A general block diagram of an assistive technology

Sensors

Perception Cognition Motor Control Effectors

Cochlea

Mic

Skull

Analog data

Digitalized data information knowledge

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68

Clinical Engineering

- An engineer who manages, maintains and improves the safe use of medical equipment in

hospitals

- It started when safety problems aroused

Electroshock, electrocution – proper grounding issue

Job Descrptions of Clinical Engineers

Supervise performance of safety testing of medical equipment by companies

Repair medical instruments

Inspect of incoming equipment

Organize inventory control

Manage calibration and repair services

Coordinate outside use of technical services

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Train medical personnel in safe and effective use of equipment

Develop and implement documentation protocols required by external accreditation

and licensing agencies

Safety Issues in Hospitals

Dangers: - Electrical Hazards

- Mechanical Hazards

- Environmental Hazards (solid, waste, noise, utilities, gas…)

- Biological Hazards: infection control (isolation, contamination, sterilization,

biological waste disposal)

- Radiation Hazards

Medical Ethics

Nature of Life and Its Significance

Immanuel Kant (1724 – 1804)

- What can I know?

- What I ought to do?

- What can I hope?

- What is man?

Ethics

- Represents the codes of conduct of society, the study of right and wrong, good and evil in

human conduct

Questions

1. Should body deformed infants kept alive?

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70

2. Should treatment be stopped to allow terminally ill patients to die?

3. Should humans be used in experiments?

Medical Dilemmas

1. Is it more important to preserve life or prevent pain?

2. Is it right to withhold treatment when doing so may lead to a shortening of life?

3. Does an individual have the right to refuse treatment when refusing it may lead to

death? (Euthanasia: good death)

Kant’s theory: Humans are owed a special kind of respect simply because they are people

Experiments

Human Ethics Review Board Animal Ethics Review Board