FAQ (Frequently Asked Questions)
Will the RadScanner Model 500 detect any
remaining radioactivity after medical radiation therapy ?
The medical profession is careful to choose
radioactive isotopes that have short half-lives to minimize exposure.
Radiation is used for two separate purposes -- therapy and diagnostic
Externally applied radiation therapy often used for cancer therapy
uses highly concentrated beams of energy from a nuclear isotope
source or a particle beam generator. Every attempt is made to expose only
the area being treated by moving a narrow concentrated beam in a constantly
moving pattern. The motion of the beam crosses through the treatment
area while dodging through the surrounding tissue. Once the treatment
session is over, no nuclear radiation remains in the treated area.
Internally applied needles with radioactive tips or tiny radioactive
pellets are placed in the center of solid tumors are left in place only
for the duration of the radiation treatment. The radioactive isotope is
chosen so that the radiation remains mostly within the tumor avoiding damage
to the surrounding tissue.
Radioactive isotopes bound to organic chemical tracers are used
in a number of specific diagnostic tests. Specific tracers will concentrate
in tumor tissue and can be viewed with detector arrays sensitive to the
gamma rays emitted. Computers process the imaging information and provide
cross-sectional views of the areas of isotope concentration.
An often prescribed cardiac stress test uses a radioactive tracer
that shows an image of the blood flow within the heart muscle. The dosage
of tracer is high enough to expose the body to an equivalent of one to
two years of normally occurring background radiation. For a day or two
after the test the Model 500 RadScanner Nuclear Detector will detect 20,000
to 80,000 counts per minute if placed directly on the body. This is 2000
to 8000 times normal background. However, the radioactive tracer decays
to half its strength in a few hours and is not detectable after 4 to 5 days.
Radiation treatment using more concentrated organically bound
radioactive iodine is used to treat overactive thyroid, since iodine
concentrates within the thyroid gland. This isotope of iodine is chosen
to have a short half-life to limit tissue damage in the normal tyroid
Is a cell phone or mobile phone radioactive?
No. A cell phone uses radio frequency (RF)
radiation which can deposit only a miniscule fraction of the energy in
a nuclear particle within living tissue. Currently, no large scale test
has proven any damage from radio frequency radiation from cell phones.
Radio frequency energy is a form of electromagnetic radiation billions
of times weaker than X-rays or gamma rays. RF energy is called non-ionizing
radiation because it cannot knock an electron free of an atom and leave
the atom ionized with a positive charge.
What are the best methods of radiation protection?
The best way to protect yourself is to know
the sources in your environment and limit contact with them. Purging
basements and enclosed spaces of radon, a radioactive gas and purging
and filtering well water from aquifers containing radioactive salts and
dissolved radon gas is important. Other natural and man made sources
of nuclear radiation are listed in the tutorial elsewhere on this Web
Knowledge of local nuclear power plants and research facilities
as well as early warning devices such as the Model 500 RadScanner can
aid in a quick evacuation before the official alert leads to highway gridlock.
Are lasers radioactive?
No. Lasers radiate light energy in the visible
and near visible portions of the electromagnetic spectrum. Laser that
emit energy in the ultra-violet (UV) region of the electromagnetic spectrum
can ionize atoms by transferring energy to outer electrons. UV energy
reacts energetically with organic compounds as anyone who has been sunburned
knows. However, by convention, this is not considered to be a radioactive
process. Short wavelength UV photons have energy levels in the few electron
volt range. To sucessfully remove an electron from a hydrogen atom takes
13.6 electron-Volts. This is known as the ionization potential. By comparison,
a diagnostic X-ray has a photon energy of 70,000 eV or more. The X-ray photon
will ionize a much greater number of atoms encountered and penetrates deeper
into tissue. Gamma rays, high energy photons, in the million electron-Volt
range are emitted by some radioactive elements.
What is ionizing radiation?
Ionizing radiation is defined as photons
from the short wavelength UV, X-ray, Gamma and Cosmic ray portion of the
electromagnetic spectrum. Of primary concern are any photons with
enough energy to damage tissue by ionizing
chemical compounds with that tissue.
Since the ionization energy of a hydrogen atom is 13.6 eV, the level around
10 eV is an approximate threshold. Since the energies associated with
nuclear radiation are far more energetic than this threshold,some in
the million electron-Volt range, then all nuclear radiation is ionizing
radiation. Likewise, x-rays are ionizing radiation, as is the upper end
of the ultraviolet range.
What does the RadScanner Model 500 detect?
The RadScanner Model 500 relies upon a gas
filled Geiger counter tube about the size of a lipstick or chapstick. The gas
is a mixture of argon with some chlorine at less than atmospheric pressure.
The tube has a center wire electrode and a metal cylindrical wall made
of stainless steel. One end has a thin mica window and the other end has
a ceramic and glass seal. A potential of several hundred volts is applied
between the central wire and the case wall. When a high energy particle
hits the tube a few of the gas molecules are stripped of some of their
outer electrons. The high voltage potential accelerates these electrons
toward the positive central wire. these electrons hit other gas atoms ionizing
them in turn and a chain-reaction or cascade results in several million
electrons reaching the central wire. This current of electrons is detected
as a single pulse or count by the electronic circuit attached to the tube.
Not all the gamma or X-rays that enter the tube initiate a discharge.
On average 3 to 5 percent will cause a detectable pulse. Almost every
alpha particles entering through the mica window will show up as a pulse.
Normally the tube detects 10 to 20 background pulses from high
energy cosmic rays and radioactive minerals in the surroundings. At 33,000
feet within a modern commercial jet, the background count rises to around
350 counts or more per minute. The airplane is flying above most of
our protective atmosphere which filters out most of the cosmic rays.
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