Seminar Topics: Biomagnetism

DISADVANTAGES OF MAGNETIC MEASUREMENT

Biomagnetism fields are much weaker than typical fields in our environment such as those produced by motor vehicles, elevators etc. The principle challenge in field measurement is from environmental noise. The most straight forward solution for shielding the magnetic noise is a magnetically shielding room (MSR).Figure10 shows an MSR

Figure 10

MAGNETICALLY SHEILDED ROOM

Biomagnetic fields are almost a billion times weaker than the earth’s geomagnetic field, thereby requiring a high performance MSR to shield out the broad spectrum of everyday RF and magnetic interference.

FEATURES AND BENEFITS

Optimum shielding effectiveness>=80db from 10Khz-1Mhz
Reliable

CONSTRUCTION

MSR is constructed of several high grade materials such as aluminium, Mu metal and copper. It has demountable construction.

SHEILDING MATERIALS

Magnetic shielding: Mu metal (high permeability alloy)
Eddy current and RF shielding: aluminium (high conductivity)
WALL: Acoustic damping
FLOORS: Vibration damping & antistatic
WEIGHT: Approximately 3400kg

MSR allows imaging equipment such as MEG system to be able to detect weak fields in the presence of much stronger environmental magnetic and RF fields. The figure11 shows the schematic view of an MSR. As shown in the graph we can see that outside the MSR, there is high field noise and inside the MSR it is very much reduced.

Figure 11

APPLICATIONS

· Storage of iron in the liver
· Particles in lungs
· Brain studies
· Heart functions

STORAGE OF IRON IN LIVER

An important application of Biomagnetism in medicine is measurement of iron concentration in liver. The liver is a major site for iron which is in the form of ferrinite and hemosiderin proteins which are paramagnetic. In earlier days, this was measured by chemical analysis in which a tissue is removed from the liver through biopsy which was painful and unsafe.

To measure the iron concentration, the basic idea is to apply a field to the region of the liver and measure the field response produced by molecules in the body tissues. The response of the tissue in comparison with the strength of applied field is called magnetic susceptibility of the tissue. Hence to determine iron concentration only the susceptibility of the liver needs to be measured.

PARTICLES IN LUNGS

Another application of Biomagnetism is the measure of the magnetic field from magnetic particles in the lungs. Well-known examples of such particles are asbestos fibers, coal dust and metal aerosols.

To detect the presence of magnetic particles, a strong magnetic field is applied over the region of lungs. The magnetic field is detected by removing the applied field and bringing a sensitive detector near the chest. The magnetic particle become magnetized in that common direction and produces a magnetic field. Then a scan of the detector over the chest gives the information about the amount and distribution of magnetic field.

BRAIN STUDIES

Brain research is the most rapidly growing application of biomagnetism. Neuro magnetic measurements can localize active regions of the brain whether other approaches have failed. Local paroxysmal discharges lead to the generation of magnetic field in the skull. These fields are calculated by means of neuromagnetic techniques.

Magnetic techniques provide a direct measure of brain activity. But it has a limitation that radial current sources are magnetically silent. Thus when a complete specification of source is required, it is better to use both magnetic and electric techniques.

HEART FUNCTION

Mapping of the magnetic field outside the chest of the subject describes the spatial and temporal behavior of MCG. These maps were first measured by Cohen and Chandler in1969. This measurement instrument was induction coil magnetometer.

In 1975 flexible magnetocardiographic measurement grid was introduced in 1975. The plannar anterior MCG measurement grid was introduced thereafter. The MCG has diagnostic capabilities comparable to that of the ECG and in several studies, it has been reported to even exceed the diagnostic value of ECG.

Based on the double relaxation oscillator SQUIDS (DROS) a 3-axis vector magnetometer system has been constructed for magneto cardiogram and mapping of MCG.

FUTURE SCOPE

A new program to image cancer and tumors in –vivo with SQUID sensor arrays and super paramagnetic nano particles is currently under development.

CONCLUSION

Biomagnetism is a boon for medicine. Biomagnetism fields result from currents or magnetization of biological tissues. Biomagnetism helps in brain study, measurement of iron concentration in liver, measurement of magnetic particles in lungs and study of heart functions.

The application of magnetic fields to human and animals is classified as not being harmful. This is not harmful status resulted from a pre-market toxicity study with MRI procedures using longer periods of exposures. A static magnetic field is an energy field is an electric field by virtue of the movements of electrons in the static electric field. This fact of the magnetic field is used in industry with predictable results and can also be used in magnetic therapy with the same predictable results.

Magnetic therapy is very efficient and have better results. Biomagnetism also have a good diagnostic value.
To conclude Biomagnetism is a boon for medicine.