Fields Lec 1
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The document discusses the interaction of electromagnetic fields (EMFs) with biological systems. It notes that the topic is studied to assess potential health hazards, enable applications in biology and medicine, and optimize the design of EM devices. The document outlines various effects of EMF exposure at different frequencies, therapeutic and diagnostic EMF applications, and the need to model human exposure and effects through governing equations and human body models. Key areas covered include dosimetry, various human body models, RF applications like keyless entry and MRI, hyperthermia modeling, and diagnostic applications such as endoscopic capsules.
![12/06/1440
5
Interaction of EMF with biological systems either to
assess health risks or for therapeutic/diagnostic
applications:
We need to:
1. The type of the electromagnetic field formulations used
to solve the electromagnetic problem: Maxwell’s eqns.
2. The source of electric, magnetic or EM field that may
induce the biological effect.
3. The use of a human body model (realistic or simplified)
with electric and thermal characteristics of biological tissues
(WHY?).
4. The computation of field quantities in different tissues
(E, J, SAR, T).
To assess human exposure or therapeutic
effects we need to evaluate:
Magnetic flux density, B [T]
Induced current density, J [Am-2]
Magnetic field, H [Am-1]
Electric field, E [Vm-1]
Specific Absorption Rate (SAR) [Wkg-1] and
tissue temperature (K) (Bioheat Eqn)
Power density, S [Wm-2]](https://image.slidesharecdn.com/lec1-200916091933/85/Fields-Lec-1-5-320.jpg)
Fields Lec 1
- 1. 12/06/1440 1 The Interaction of EMFs with Biological Systems Why Study EMF? Interaction of EMFs with biological systems. Health hazard prevention Applications in biology and medicine Design of EM devices and optimization What do you think??? Cell phone usage (the more the better) Living under base stations or in front of them Exposure effects of low frequencies versus high frequencies (are they the same)
- 2. 12/06/1440 2 Assingment # 1 List as many applications of magnetic biosensors in the BME field (figures and theory of operation should be listed) There will be a prize for the largest number found. Please bring TO CLASS next time Interaction of EMF with Biological Systems Interest was motivated by: 1. Possible Human health hazards: Adverse effects at low frequencies as well as high frequencies. 2. The successful applications of EMFs in therapy and diagnostics. Low frequency fields (0-3kHz) High frequency fields (RF and microwaves) 3. Wireless applications (Telemetry)
- 3. 12/06/1440 3 Onset of childhood Leukemia Cardiac fibrillation Vision of phosphenes Nerve and muscle stimulation Interference with implanted medical devices: - Pacemakers (time varying fields) - Orthopedic prosthesis like metal bars or screws in bones (static fields)(Like can occur in ? device) Adverse Effects: due to the exposure at power line frequencies (50/60 Hz) or in the industrial environment (power transformers, electric appliances, welding equipment, etc.) Mobile Phone Exposure (0.9- 2.2 GHz): EMF risk assessment: Different approaches for assessment of EMF emitted by devices performed under well defined and controlled lab conditions. (WHY Lab?)
- 4. 12/06/1440 4 Cellular Phones – Human Interaction SAR TEMP Therapeutic and diagnostic applications Postponed to the end of the lecture (slide 21)
- 5. 12/06/1440 5 Interaction of EMF with biological systems either to assess health risks or for therapeutic/diagnostic applications: We need to: 1. The type of the electromagnetic field formulations used to solve the electromagnetic problem: Maxwell’s eqns. 2. The source of electric, magnetic or EM field that may induce the biological effect. 3. The use of a human body model (realistic or simplified) with electric and thermal characteristics of biological tissues (WHY?). 4. The computation of field quantities in different tissues (E, J, SAR, T). To assess human exposure or therapeutic effects we need to evaluate: Magnetic flux density, B [T] Induced current density, J [Am-2] Magnetic field, H [Am-1] Electric field, E [Vm-1] Specific Absorption Rate (SAR) [Wkg-1] and tissue temperature (K) (Bioheat Eqn) Power density, S [Wm-2]
- 7. 12/06/1440 7 hQJETk t T c Bioheat Equation )( blb TTh T k n Heat transfer coefficient Blood temperature Density Specific heat Thermal conductivity Time Temperature Current density Electric field intensity heat loss to blood perfusion VARIABLES Heat Change MATERIAL PROPERTIES EJ Electrical conductivity Density Specific heat Thermal conductivity Time Temperature Current density Electric field intensity heat loss to blood perfusion heat loss to blood perfusion Heat Conduction Joule Heat Various Human Body models Norman Zuabl Brooks Hugo Human Head Model
- 8. 12/06/1440 8 Low Frequency Dosimetry Acquisition Segmentation Reconstruction Ella head model
- 9. 12/06/1440 9 Electromagnetic Modelling of the Human Body Phantom Development – NORMAN NORmalised MAN Height: 1.76 m Weight: 73 kg Developed from MRI scans 8.3 million voxels (2 mm)3 37 different tissue types Frequency dependent conductivity and permittivity Also scaled to represent children at ages 1, 5 and 10 years Example: Power Absorption from Radiofrequency Fields Relative contributions of the body parts to whole-body SAR Individual SAR values expressed as a rainbow spectrum: violet = lowest, red = highest absorption gradually moves awayincreasesAs frequency from knees and ankles to the upper torso
- 10. 12/06/1440 10 Keyless Entry: A wireless device for remotely locking and unlocking the vehicle Never Underestimate the Power of the Chin 315 MHz ,a simple radiating loop antenna EM Field Exposure from a monopole antenna placed above the trunk of the car (SAR in an axial slice of the head)
- 11. 12/06/1440 11 Magnetic Resonance Imaging Imaging Devices (???)
- 12. 12/06/1440 12 Full 3D simulation model including human model and RF shield of gradient coil The problem with 7T MRI... (High power…. SAR limits reached) -Advanced multi- channel coils are required. (Biomedical Engineers) Assignment 2 Visit this site: https://www.itis.ethz.ch/virtual- population/virtual-population/overview/ What did you find? https://www.itis.ethz.ch/customized-research/ List the research topics you found? Be prepared to discuss in class
- 13. 12/06/1440 13 Applications of EMF at 100 MHz – 30 GHz Examples of some HT applicators
- 14. 12/06/1440 14
- 15. 12/06/1440 15 BSD Deep Heating Hyperthermia Modeling
- 16. 12/06/1440 16 3D Treatment Plan 1. Segmentation of images 2. Stacking of MR/CT images 3. Positioning of Antennas 4. SAR calculation 5. Temperature Distribution SAR
- 17. 12/06/1440 17 Hyperthermia Results Electric Field Temp Brain Tumor Hyperthermia Geometry Tissue parameters Boundary conditions Numerical modeling Prototype Head Model Antenna Chamber
- 18. 12/06/1440 18 Temperature distribution in head tissues
- 19. 12/06/1440 19 C. Coil 1 Coil 2 Induced E field
- 20. 12/06/1440 20 Cardiac ablation RF Cardiac Ablation J
- 21. 12/06/1440 21 RF Hepatic Ablation Liver Stainless steel trocar Insulated trocar 4 tines of electrode Blood vessel (10 mm) A B Temperature Distribution Highest temerature
- 22. 12/06/1440 22 Electro-Osteo-Stimulation Magnetic nanoparticlesDrug targeting of magnetic nanoparticles to treat intramedullary spinal tumors) :To be discussed in class http://uicscience.tumblr.com/post/176482290873/ video-created-by-adriana-orland-a-student-in-the
- 23. 12/06/1440 23 Biological Effects of Diathermy 1-Increased metabolism. 2-Relief of pain. 3-Stimulated wound healing. 4-Relaxed muscle spasm. 5-Accelerated wound healing. 6-Decreased haematoma formation
- 25. 12/06/1440 25
- 26. 12/06/1440 26 Course Outline Electrostatic fields Magnetostatic fields Time-varying fields Electromagnetic waves (antennas and propagation in different media) Antennas: therapy, diagnosis, telemetry Electrical and thermal properties of biological tissues Therapeutic applications in biology and medicine (challenges) Numerical modeling
- 27. 12/06/1440 27 References Elements of Electromagnetics (Sadiku) Basic Introduction to Bioelectromagnetics (Cynthia Furse)