Effects of Radiation
Radiation Symptoms occur because of overexposure to radiation. Most are familiar with the effects of spending too much time in the direct sunlight on a hot summer’s day – the result is a sunburn. Sunburns occur when an individual’s skin is overexposed to the sun and the medical community has gone to great lengths educating people on the harmful effects of the suns radiation. These harmful effects vary from the uncomfortable red, enflamed skin to severe blistering demanding medical treatment. So how does one prevent a sunburn? Spend less TIME in the sun. Cover up your skin with clothes, shade, or sunscreen (SHIELDING). This sounds a lot like the ALARA principle of TIME, DISTANCE and SHIELDING.
We can feel the gentle warmth of the sun’s rays on our body, but the damage being done is slow and the pain is a delayed response to the overexposure of sunlight. Likewise, the ionizing radiation of gamma and x-rays is invisible, it has no smell, but unlike the sun – it cannot be felt at all.
Biological effects of radiation fit into two general categories:
- Acute radiation exposure is when an individual receives a high radiation dose over a relatively short period of time. Acute radiation exposure also called Acute Radiation Syndrome (ARS). ARS results when an individual receives a whole body exposure of 100 to 200 Rems or more (Roentgen Equivalent Man) over a 24-hour time period. The table below shows the likely symptoms associated with differing levels of exposure.
- Chronic radiation exposure occurs over an extended or prolonged time and the results vary depending on the dose of exposure, duration of exposure and individual reaction to the over-exposure.
Roentgens (R), Radiation Absorbed Dose (RAD), Roentgen Equivalent Man (REM), and Quality Factor (QF) are units of radiation measurement and it is important for the radiographer to discern between them each.
Roentgens (R), is the unit of measuring radiation exposure in AIR for X-rays and gamma rays, which is based on the ionization produced in air. More specifically, the Roentgen is defined as “the radiation flux which will produce 2.083 x 109 ion pairs per cubic centimeter (one electrostatic unit of charge either positive or negative) at a standard temperature and standard pressure (0° C and 760 mm Hg). But for all practical purposes – commit to memory that Roentgens measure ionizing radiation in air.
Radiation Absorbed Dose (RAD) is the accepted unit of measurement of absorbed dose in tissue. 1 RAD represents 100 ergs of energy imparted per gram of material at the place of exposure.
Quality Factor (QF) is a factor or multiplier of the actual biological effects or damage of the specific radiation type on the human tissue. In a sense, not all Roentgens impart equal damage to tissue and therefore we use a QF multiplier to calculate for the Roentgen Equivalent Man (REM). Table 7A below will demonstrate the various QF value of differing ionizing radiation sources.
Roentgen Equivalent Man