Side Effects of Radiotherapy or Overexposure to Radiation

The x-rays and radiation from the radioisotopes play a great role in diagnostic procedures and therapy, but the exposure exceeding certain limits do have side effects on our body as elaborated below:

1. Skin Reaction: The maximum permissible dose (MPD) for the skin is 100 rads. When a limited area of the skin receives a dose of a few times of MPD within a few days, that may result in the production of erythema and the reaction may stay for a week. A dose of about 1000 rads may cause tanning of skin and hair fall. A dose in the range of 2000 rads to 3000 rads may cause permanent tanning of skin and hair loss. There is possibility of atrophy of sweat glands and serious ulcers.


2. Radiation Sickness: Even a single exposure of 50 rads or more to the trunk or entire body may cause malaise, nausea, vomiting and diarrhea, collectively called radiation sickness. Some people may not be affected at this dose, however effect may be severe at a whole body exposure at 200 rads.


3. Effects on Blood: A single exposure of 25 to 30 rads to the whole body or to the major bones/bone marrow may result in mid to moderate leucopenia (low count of white blood cells in blood), but recovery is there. A dose of 200 to 500 rads to the spinal marrow may cause leukemia in some cases. Keep in mind that the radiations have accumulated effect.


4. Production of Cataract: Excessive exposure of eyes to radiations with an accumulated dose of 100 to 200 rads could impair our vision and cause cataract.


5. Production of Sterility: Even a shorter time exposure to the radiations around 500 rads to the genital organs may cause permanent sterility in either sex. A long term exposure to lesser dose of radiations may also lead to secondary infertility in either sex.


6. Exposure during Pregnancy: Although there are a number of cases receiving radiotherapy for pelvic cancer during pregnancy and delivering normal babies, but a pregnant woman receiving a very large dose of radiation in order of 1000 rads within a few weeks may have a miscarriage or still birth. The possible effect on the fetus may vary with the period of gestation. Congenital abnormalities may affect the babies so pregnancy should be avoided during radiotherapy of pelvic cancer.


7. Genetic Hazards: Irradiation of ovaries or testicles may lead to mutations in genes and affect reproduction. Greater is the exposure, the greater are the chances of genetic abnormalities.

Personal Monitoring of Radiation Professionals

All persons associated with commercial, diagnostic or therapeutic use of radioisotopes or radiochemicals, x-rays or other sources of radiation could be labeled as radiation professionals or radiation workers. Excessive exposure to radiation beyond the maximum permissible dose (MPD) for a person of a particular age may lead to serious healthy problems. The maximum permissible dose [MPD=(N-18)x5=?Rads; where N stands for the age in years] to the whole body, at any age is equal to 5 times of the number of years beyond 18 years. The MPD in consecutive three months should not exceed 3 rads. The accumulated MPD is also the MPD for the head and the trunk of a person associated with the handling and use of radiochemicals or radioisotopes or operating radiation equipments.

The dose received by any individual is ascertained by various types of monitoring procedures. The most commonly used are film badges and small ionization chambers. The film badges and small ionization chambers are supplied and monitored by many commercial firms.

Film Badges:

The film badge is a small packet of photographic film which is sensitive to radiation; or it may be containing two pieces of photographic films of different sensitivities. A part of these films is covered by one or more metal filters to resist the beta radiation and the other part is open to the beta radiation exposure. For x-rays a different type of film and filter is employed in the film badge. The film badge is worn by the person while handling the radiochemicals or operating radiation equipments. The darkening of the film of the film badge is related to the radiation dose received by a worker. Under the open window it gives the effect of beta radiation and under the filter the effect of gamma radiation or high energy x-rays.

Small Ionization Chambers:

The ionization chambers used for the personal monitoring are small instruments about the size and shape of a fountain pen. These are also called "pocket dosimeters". Before putting to use these are charged with electric pulse from a special charger. The charging transfers the electrical charge to the insulated wire inside the pocket dosimeter. The principle of the functioning of an ionization chamber or pocket dosimeter is that on exposure to the radiation the charge on the insulated wire inside it would decrease.

Physical Properties Of Some Radioisotopes Used In Medical Field

There are about two dozen radioisotopes finding their use in medical diagnosis and treatment. Here is a list of physical properties of these radioactive isotopes. The list could be beneficial for the students of radiation science.

Physical Properties of some Radioisotopes

The radioisotopes available as mixed with stable isotope from the same element and are called carrier radioisotopes and those available as free from any stable isotope are called carrier free radioisotopes. The carrier free radioactive chemical may contain many milliCuries (mCi) of radiation energy in a few milligrams (mg) of chemical. The radioactive iodine (¹³¹I) used in the treatment of hyperthyriodism (hyperactivity of thyroid gland) and evaluation of thyroid function should be carrier free or nearly so.