general bio medical engineering

8/14/2019 General Bio Medical Engineering

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Mannheim BiomedicalEngineering Laboratories

Prof. Dr. Markolf Niemz- Lecture notes -

- Exam preparation -

Introduction / literatureChap. 1: BiomaterialsChap. 2: BiosensorsChap. 3: Ultrasound

Chap. 4: RadiologyChap. 5: Magnetic resonance


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Biomaterials

natural cell smallest unit of life capable of independent existencetissue group of similar cells plus extracellular materialorgan group of tissues with a common function

natural (artifically put in place) transplant transfer of natural tissue or organ

artificial implant assistance to natural tissue or organprosthesis replacement of natural tissue by substitute


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Natural biomaterial

example: human skinEpidermis

Dermis

Subcutis

cell

cell

cell

tissue

tissue

tissue

O

R

G

A

N


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Organ systems

type organs function

circulatory heart, blood vessels, blood transport of bloodrespiratory nose, pharynx, trachea, bronchi, lungs exchange of O 2 and CO 2digestive mouth, esophagus, stomach, intestines digestion of nutrientsurinary kidneys, ureters, bladder, urethrae regulation of plasma compositionmusculoskeletal bone, cartilage, tendon, skeletal muscle support and movement of bodyimmune thymus, lymphoid tissues defense against foreign invaders

nervous brain, spinal cord, nerves coordination of activities, consciousnessendocrine all glands secreting hormones regulation of activitiesreproductive testes, penis, ovaries, uterus reproductionintegumentary skin protection, control of temperature


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Transplants, implants, prostheses

transplant still natural tissue or organ, transferred from same patient or from donor to recover function of diseased or removed tissue or organ e.g. blood, bypass, heart, liver, skin

implant artificial tissue, alloy, glass, metal, or electronics to assist function of diseased tissue or organ e.g. contact lens, hearing aid, hernial mesh, inlay, pacemaker, stent

prosthesis artificial tissue, alloy, glass, or metal to replace diseased tissue e.g. denture, hip, joint, knee, leg


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Artificial biomaterials

material advantage disadvantage application

polymernylon ductile not strong suturepolyester light prone to creep vascular prosthesissilicone easy to fabricate degradable breast prosthesis

metalTi, Ti alloy, Co-Cr alloy partly ductile prone to corrosion artificial jointstainless steel strong release of ions bone plate, screwAu, Ag, Pt tough dental root implant

ceramiccarbon biocompatible brittle, fragile inlay

aluminum oxide inert weak in tension denturehydroxyapatite stiff orthopedic prosthesis


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Artificial biomaterials part II

material advantage disadvantage application

compositecarbon polymer strong difficult to fabricate heart valvemetal-PMMA customized high cost bone cement

bioactive glassBioglass R directly bonds to brittle, fragile middle ear device

human bone jaw repair

bioactive glass-ceramic directly bonds to brittle, fragile spine surgeryCerabone R human bone hip surgery


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Biomechanics

Hookes law for elastic solids: = E

with stress (Pa), modulus of elasticity E (Pa), and strain

/ 2 / 2

L

L + L = L / L

tissue

tissue


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Biomechanics part II

stressstrain curves forbrittle and ductile materials

Hookes law:= E

toughness: d

slope:

modulus of elasticity E (Pa)Strain

S t r e s s

( P a

) BrittleDuctile

Material failure

Toughness


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Biosensors


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Thermosensors

Hg thermometer RTD thermistor thermocoupleexpansion: 1.82 ml / oC resistive temp. detector semiconductor two metals


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Thermosensors - part II


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ECG: Precordial leads


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ECG waves


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ECG: Normal

criteria of normal ECG: P and T waves upright in lead I q < 20 ms in leads I and aVL

QT interval < 0.44 s PR interval < 0.2 s


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ECG: Myocardial infarction

criteria of myocardial infarction: R wave absent in leads I or V2 V5 ST segment elevated in V2 V5 T wave inversed in V2 V5


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EEG: Standard waves

type frequency location normal adult normal child(Hz)

alpha 7.5 13 posterior eyes closed eyes closed

beta > 14 anterior alert alert

theta 3 7.5 all leads asleep < 13 years

delta < 3 anterior asleep < 1 year


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EMG: Electromyography


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EOG: Electrooculography

provides measure of retinal function voltage U int corresponds to illumination U int is estimated by measuring U ext U ext is measured when eye looks from side to side

Arden ratio: maximum voltage under light adaptionminimum voltage under dark adaption


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Ultrasound

ultrasound: > 20 kHz


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Ultrasonic transducer

piezoelectric effect:electric field mechanical force

mechanical force electric field

electric field: voltagemechanical force: contraction, strain

piezoelectric materials:e.g. quartz, polyvinyldifluoride (PVDF)


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Ultrasound: Reflection and refraction

c velocity wavelengthf frequencyZ impedance

density

velocity: c = f

impedance: Z = c

law of reflection: i = r

law of refraction:sin isin t

=c1c2

=12

reflection: R =Z2 cos i Z1 cos tZ2 cos i + Z1 cos t

transmission: T =2 Z 2 cos i

Z2 cos i + Z1 cos t

normal incidence: R = Z2 Z1Z2 + Z1T = 2 Z 2Z2 + Z1


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Ultrasound imaging: A-mode and B-mode

signal: voltagedisplay: a mplitudes

signal: voltagedisplay: b rightness


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Doppler ultrasound


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Radiology

computed tomography (CT):x-ray

nuclear medicine: , , , neutron, heavy ion


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Electromagneticspectrum


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X-rays

type transition

K L K

K M KK N K. . . . . .L M LL N L

L O L. . . . . .M N MM O MM P M. . . . . .


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CT scanner

rotation: 360 o aperture of gantry: 60 70 cm


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Medical x-ray applications

organ indication

blood vessel bleedingbone complicated fracturebrain hematoma, tumorintestines tumor, metastasesliver cyst, tumor, metastaseslung tuberculosis, tumor, metastaseslymphoid tissue metastasesspine herniated disctooth caries


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Nuclear medicine

N: nucleus

A: number of protonsand neutrons

Z: number of protons

AZ

type of decay Z A example

2 4 226 Ra 222Rn + + 1 0 32P 32S + + 1 0 11C 11B + + 0 0 99Tc 99Tc + e capture 1 0 p + e n


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Radiation safety

traditional units SI units

activity Curie (Ci) = 3.7E10 dps Becquerel (Bq) = 1 dpsabsorbed dose Rad = 0.01 J/kg Gray (Gy) = 1 J/kg

dose equivalent Rem = Rad Q Sievert (Sv) = Gy Q

dps = disintegrations per secondQ = quality factor

target exposure limit

public 1.5 mSv/yearradiation controller 5.0 mSv/yearradiation worker 50 mSv/year


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Radiation safety - part II

quality factor Q

20

1

1

10


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Spin and magnetic moment

nucleons (protons and neutrons) have a quantum property known as spinspin L is analogue of momentum ptorque = L / t is analogue of force F = p / t

spinning nucleon causes magnetic moment spinning nucleons cause magnetization M =


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MR active elements in tissues

half integer spins:odd mass number

integer spins:even mass number andodd atomic number


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T1 images vs. T2 images

signal T1 image T2 image

bright fat water , blood, liquor, edema

middle muscle, cartilage, marrow fat , marrowdark water , blood, liquor, edema, bone, calcification muscle, bone, calcification

tissue T1 (ms) T2 (ms)

fat 160 100white matter (brain) 380 85gray matter (brain) 520 95water , edema 600 150

malignant tumor 800 200


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Gradient echo sequence


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Spin echo sequence


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Mannheim Biomedical

Engineering Laboratories

MR instruments

B 1 2 Tesla1 Tesla = 10 000 Gaussearth: 0.5 Gauss MR scanner with superconductive magnets


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Mannheim Biomedical

Engineering Laboratories

University Mannheim Technical Universityof Heidelberg Medical Center of Mannheim

Biomedical engineering: characterization and processing of biomaterialsinternet database for tissue parameters

Medical physics: design of medical applicators and sensorsbioelectrical multichannel measurement devices

Laser medicine: laser-tissue interactionsmedical applications of ultrashort laser pulses

general bio medical engineering

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