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