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MAGNETIC FIELDS BASICS
Biomagnetic Fields
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The body produces its own very complex electrical
activity. Wherever there is electrical activity MFs result. The
body's own magnetic fields are extremely tiny. They are so tiny
that they are easily obscured by the surrounding planetary and
environmental fields. These external fields have to be blocked
to allow study of the body's own magnetic fields. The endogenous
electrical and magnetic fields of the body regulate all the
body's processes and interact with each other. Unlocking these
secrets opens new alternatives in diagnosis and treatment. |
Biomagnetometers
There are many devices for measurement of
electrical fields, including electroencephalo- grams (EEGs) and
electrocardiograms (EKGs). There are significant limits to the
information able to be gained from these, especially at the
local cellular level. Electrical field measurement does not
localize small areas of pathology as well as MF measurements can
and can't "see" as deep into the body without having
to insert probes. Also, electrical measurements capture voltage
but magnetic measurements say more about total current, which is
more physiologically relevant. Biomagnetic fields are minimally
affected by tissues along their paths, such as the skull, as
opposed to bioelectric fields. Biomagnetometers, do not require
electrode placement and allow intracellular currents to be
measured compared to extracellular voltage charges. Thus MF
measurement allows for measuring transmembrane charges without
penetration of the cell membrane. It therefore becomes easier to
detect electric currents flowing within a person by detecting
the associated MFs than by recording surface electric charges at
the skin. This allows for accurate, non-invasive assessment of
function or pathology,
 Magnetically
shielded rooms have been created that made it possible for new
devices called SQUIDS to actually measure and map the fields of
the whole body and its organs.
Magnetic shielding requires the use of new
artificial metals, called "mu" metals, combined with
other metals, to get as close as possible to zero magnetic
fields. SQUIDS are super-conducting Quantum Interference
Devices. They are based on the discovery in physics of "Josephson
Junctions" in super-conducting materials. The SQUIDS allow
measurement of extremely tiny electrical and magnetic fields.
Magnetically shielded rooms
Laboratories are very magnetically and
electrically "noisy" environments. Even, remote
natural environments are still "noisy" relative to the
body's fields The sensitivity of the SQUID and the amount of
shielding determine how small the fields are that can be
measured.
The body's natural MFs
The strength of the body's fields in relation to
the strength of the Earth's magnetic field is shown in the table
below.
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Strengths of endogenous magnetic fields versus Earth's
field
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| Signal source |
FemtoTesla |
Gauss |
Earth's field stronger by |
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Skeletal Muscle
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~50,000 |
0.0000005 |
1 million times |
| Heart |
~500,000 |
0.000005 |
100,000 times |
| Physiologic "noise" |
50,000-5,000,000 |
0.0000005 0.00000005 |
1 - 10 million times |
| Earth's field |
50,000,000,000 |
0.5 |
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As widely known elsewhere in
science and engineering, externally applied electric and
magnetic fields interact with and affect each other. The body's
own biomagnetic fields have both time-varied (frequency) and DC
components. While externally applied DC fields need to be
stronger than the surrounding geomagnetic field to exert
additional impact on the body, time-varied magnetic fields (TMF)
can be much weaker than the Earth's background field. In fact,
the lower limits of strength of weak TMFs to have biologic
effects have not been defined. What is known is that TMFs much
weaker than the Earth's field have been shown to exert actions
on the body, even probably to the picoTesla level, and maybe
even to the femtoTesla level. Much instrumentation for
treatment, including those used in the studies described in our
book "Magnetic
Therapy in Eastern Europe: a review of 30 years of research"
uses fields that are in the mT range (10's to 100's of
Gauss). These EMFs are 1000 to 10's of thousands times stronger
than the Earth's magnetic field. That means, for TMFs, they are
10's to 100's of millions times stronger than the body's own
EMFs. The clinical use of EMFs will be dealt with in the Health
Topics section (((link))). This is
one of the key factors in getting a sense that these
"clinically useful" fields are strongly active in
stimulating physiologic processes in the body.
Diagnostic use of biomagnetic
measurements
The finding through objective basic research of
these endogenous fields not only allows us to know what their
magnitudes are but also has allowed the development of new
non-invasive means of measuring cellular function. The technical
ability to obtain sensitive, natural biomagnetic measurements
has already allowed use in medicine, especially
magnetoencephalography (MEG). MEGs are used for helping
neurosurgeons localize areas of the brain causing epileptic
seizures. Studies are being done to evaluate cardiac function
and pathology (magnetocardiography). Other applications are
being considered, including measuring tissue iron loads in lung
and liver. Muscle and other nerve function measurement systems
are also possible in the future.
There is a web site about the use of
biomagnetics in
neuroimaging.
This is a website for cardiac imaging:
www.lib.hut.fi
More information is available from the book
"Advances in Biomagnetism"
, edited by Williamson, SJ.
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"Time-varied
magnetic fields (TMF), much weaker than the Earth's
field, have been shown to exert actions on the body." |
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