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 testing.

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 tissue.

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 site.

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.

PROGRESSIVE SYSTEMS COMPANY 1620 West Main Street  Houston, Texas 77006-4712
Tel:  713 523 0515  
email:  daniel-s@swbell.net   www.antirad.com

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