Bio Magnetism (Btech seminar)

BIO-MAGNETISM

Anurag Chand 10607032

OUTLINE INTRODUCTION  BIOMAGNETIC THERAPY  INSTRUMENTATION OF BIO-MAGNETS   TYPES OF SQUIDS  WORKING  APPLICATIONS OF SQUIDS  ADVANTAGES  DISADVANTAGES OF MAGNETIC MEASUREMENT 

Introduction 

Bio-magnetism is a new field of research dealing with the measurement and interpretation of magnetic fields produced by organs or by magnetic contaminants of the body



Some examples are:  The The bio-magnetic fields arising from ironbearing proteins in human liver. Magnetic contaminants may be found in the lungs and stomach

BIOMAGNETIC THERAPY  

 The healthy tissue produces a distinct negative, negative, micro micro voltage. When trauma, stress or malfunction occurs, the potential changes to a positively charged state .  The nervous relay system immediately transmits the relay to the brain, which floods the problem area with healing negative charges to correct the chaotically charged area



 The metabolism process in each cell is dependent on biopotential in this cell



 The negative field of a magnet is used to correctly correct ly correctly stimulate & create the healthy cellular charge state of a strong negative potential. Hence the need for properly designed biomagnetic field.

Current in the body is not like current through a wire. (A)  It is expressed as current dipole (mA-m)  A current dipole consists of a source at the dendrite and a sink at the soma.  The distance between source and sink determine he impact of current dipole 

on the other dipole in the surrounding s urrounding tissue.   The total effect produces two current patterns of opposite polarity, one outward and the other inward, hence the name ‘current dipole’.

INSTRUMENTATION 





Super Conductivity Quantum Interference Device (SQUID) is a magnetometer used to measure extremely weak magnetic field.  Threshold for SQUID: 10^-14 T Magnetic field of brain: 10^-13 T Magnetic field of earth: 2.5x10^-8 SQUID is an assembly of 

 Josephson junctions within a superconducting ring.



 The Josephson junction is composed of two superconductors separated by a thin insulating layer.





Electrons can tunnel through the insulator. Hence current crosses the junction across superconductor despite insulator. This is Josephson Effect.

 There are two main types of SQUID (1) Direct current (DC) –Two Josephson Junction used (2) Radio Frequency (RF)- One Josephson Junction used

DC SQUID 

Phase changes with changing magnetic field.

So does the super current around the ring and thereby voltage.   The change in flux crossing across the ring is quantized.  The The quanta of flux is given by

RF SQUIDS Uses only one Josephson junction .  Less sensitive compared to DC SQUIDS  Widely used due to less cost   The RF SQUID is coupled to a resonant tank circuit . As the SQUID operates the effective inductance of the tank circuit changes and thereby resonant frequency changes.  Output voltage is sinusoidal with linear variation in flux. 

Structure of SQUIDs

APPLICATIONS OF SQUIDS MEASUREMENT OF IRON IN LIVER   The The liver liver is is aa major major site site for for iron iron which which is is in the form of ferrinite and hemosiderin protein which are paramagnetic  PARTICLES IN LUNGS Well-known examples of such particles are asbestos fibers, coal dust and metal aerosols. 

MEDICAL IMAGING  



Computerized Tomography (CT) Magnetic Resonance Imaging (MRI) Positron Emission Tomography (PET)



MAGNETOENCEPHALOGRAPHY (MEG) Measures the magnetic fields produced in the brain by ionic current flow arising from neural activity.



COMPARISION OF MEG, MRI & PET



MAGNETOCARDIOGRAPH (MCG) Used for heart monitoring.

Heart produces a rhythmically synchronized synchronize d signal. This signal is described by means of a current dipole. SQUIDS pick up the magnetic signal. Signal is then amplified and sampled and then fed to processor

ADVANTAGES OF MAGNETIC MEASUREMENT    



Non- invasiveness Quick measurement Good spatial resolution. MCG exceeds the diagnostic value of  ECG. Magnetic field is less than distorted by tissues than the electric potential.

DISADVANTAGES OF MAGNETIC MEASUREMENT  





Environmental noise Most effective solution is a magnetically shielding room (MSR). Magnetic shielding: Mu metal (high permeability alloy) Eddy current and RF shielding: aluminum (high conductivity)

FUTURE SCOPE 



A new program to image cancer and tumors with SQUID sensor arrays and super paramagnetic nano particles is currently under development. Biomagnetism also have a good diagnostic value.

REFERENCES I.P.Wiksow, Jr; “SQUID magnetometers for Biomagnetism and Nondestructive Testing”: Important Questions and Intial Answers. –IEEE  Transactions on Applied Super Conductivity Vol 5, No:2,June1998  Handbook of Biomedical Instrumentation, I nstrumentation, R.S.Khandpur  www.biomagnetism.com 

 THANK YOU