Radiation Safety

Created by: Adam Evearitt M.S., DABR

Medical Physicist

Radiation Basics» Radiation (def.) – The

process of emitting energy in the form of waves or particles.

» Radiation can come from radioactive material, or it can be produced through electrical interactions

» Radioactive material can emit particles or waves.

» X-ray machines emit waves of radiation.

Radioactive Material» Radioactive material is a substance

that emits radiation. » Radioactive material (like radon or

uranium) is very dangerous, because if it gets on or in your body it will constantly be emitting radiation right on you.

» The radiation itself passes through your body just one time and deposits its energy as it goes through.

» There is no residual or remaining radiation after it passes.

Radioactive Waves» Radioactive waves are made out of massless particles called

photons» The waves can travel at different frequencies» The range of frequency of photon radiation is called the

electromagnetic spectrum

Ionizing Radiation» Radiation that has a high enough frequency to

change the atoms of the material it passes through is called ionizing radiation.

» It does this by ejecting an electron from the atom» Once the atom is ionized, it will want to interact

and change other atoms. This is when radiation becomes dangerous.

Radiation Units»Roentgen (R) – Ionizations in air – usually used in Geiger counters or detectors (like mR/hr)

»Rad – Radiation Absorbed Dose – energy per unit mass in any object

»Rem – Radiation Equivalent Man – Dose to the human body (Rad multiplied by a quality factor)

»Curie or Bequerel – disintegrations – used for radioactive material

»This presentation will use the unit mrem, because it is the most common unit used for dose reporting with dosimeters.

» mrem or mRem stands for millirem (1000 mrem = 1 Rem) – just like a millipede has a thousand legs!

» The difference between the Rad and the Rem is that the Rad just considers each ray or particle emitted, and the Rem looks at not only how much is emitted, but what that radiation can do to the human body.

» Here is a visual example of how different types of radiation can cause more or less damage per emission. » Once the DNA is damaged, it will either kill the cell, or cause a mutation that could turn into cancer.

Because the bigger particle can deliver more damage to a cell, we multiply the dose (in rads) by a quality factor (like 20) to get the dose as it relates to a human cell (in rem)

Radiation Damage

Biological Effects»The human body can repair itself after damage done by radiation »Scientists are unsure whether additional low levels of additional radiation are really harmful to us or not. »Some people even believe that low levels of radiation actual provide a benefit to the body. This is called radiation hormesis.

Background Radiation» Man-made x-ray machines are not the only things that create ionizing

radiation. » We also get exposure to ionizing radiation from the sun (cosmic rays),

radon gas in the earth, and even our own bodies (like radioactive potassium that we’ve eaten).

» We call this background radiation.

Radiation Amounts

Radiation Amounts» The amount of radiation that a patient gets from routine exams like

dental x-rays and chest x-rays can be comparable to the amount of radiation they get from other things in life

» There is no road sign as you enter Denver that says, “If you are pregnant or think you may be pregnant, please move to Chicago.”

A single Dental (intraoral) x-ray 0.4 mrem

Watching TV (on an older model – not flat screen)

1.0 mrem per year

5 hour airplane flight 2.5 mrem

Chest x-ray 10 mrem

Mammogram 44 mrem

Living in Denver vs. Miami 50 mrem per year

CAT scan of the body 1000 mrem

Biological Effects» There are two categories of effects that can be caused by

exposure to ionizing radiation. They are called Stochastic and Deterministic (or Somatic) effects. Both of these types of effects can have short and long term consequences.

» Stochastic effects are the problems that can happen just by

chance - like if the radiation hits the DNA in the cell just right so that it turns into a cancer cell. We cannot predict when these effects are going to happen.

» Deterministic effects are problems that are directly determined by the dose a person gets. We know that a certain amount of radiation will produce a certain effect like reddening of the skin or cataracts.

Biological Effects

Dose (mrem) Effect

0 - 5000 No visible effects

8000 – 12,000 Vomiting/Nausea (1-10%)

13,000 – 17,000 Vomiting/Nausea (25%)

18,000 – 22,000 Vomiting/Nausea (50%)

27,000 – 32,500 Vomiting/Nausea to all exposed. 50% death in 60 days if untreated

40,000 – 50,000 Vomiting/Nausea to all exposed. >50% death in 60 days if untreated

55,000 – 75,000 Vomiting/Nausea within 4 hours. 100% death if untreated

100,000 Vomiting/Nausea within 1-2 hours. 100% death if untreated

500,000 Vomiting/Nausea within immediately. 100% death in 48 hours if untreated

» We know much more about the effects of high doses of radiation than we do about low doses.

» Scientists have studied the atomic bomb survivors, Chernobyl survivors, early radiologists, and radiation therapy patients.

» Every several years, the data is published in a report called the BEIR (Biological Effects of Ionizing Radiation) report which is available through the National Academies Press.

» The following table is for Whole Body radiation

Radiation Induced Cancer» A dose 20,000 mrem is known to raise the risk of

developing cancer 0.2 – 1.6%.

» The natural risk we all have of developing cancer some time in our lives is 33%.

» Radiation exposure is known to increase the risk of

leukemia.

» Radiation can induce many different types of cancer throughout the body, but it is difficult to make a direct connection because the cancer may appear 50 years after exposure.

ALARAHigh levels of radiation are bad for the human body. We don’t really know if low levels are good or bad, so the general policy of the government regulations and recommendation by physicists is to treat all extra radiation as bad radiation.

People that work with or around radiation should use the concept of ALARA (As Low As Reasonable Achievable). This means that you should only use as little radiation as possible to get the desired results.

Practically speaking, it means things like x-ray techs doing their best not to repeat x-rays by getting good images the first time, or dental offices using lead shielding on the patients because it isn’t necessary to expose the body to get pictures of the teeth.

Radiation and Pregnancy» Pre-conception radiation to the gonads of either parent has

not shown to result in an increased risk of cancer or malformations in children.

» A fetus is vulnerable to radiation due to the rapid division of the cells, and the risk is higher during the earlier stages of pregnancy when the mother may not even know she is pregnant.

» It is so important to provide lead shielding to all women of reproductive age.

During the very early stages of the first trimester, radiation may induce a spontaneous abortion. At about 8 – 15 weeks, radiation doses of 10,000 – 15,000 mrem may cause neurological problems. Doses at 10,000 – 50,000 mrem may also cause malformations in the fetus. There have been studies that show a 4% decrease in IQ for every 10,000 mrem. It is important to note that these levels of radiation cannot be achieved with typical x-ray exams at a doctor’s office or a dental office. Three CAT scans directly on an expectant mother’s pelvis just reach these levels. However, these sorts of x-ray doses can be reached with certain lengthy fluoroscopy procedures and with radiation therapy.

Radiation and PregnancyAdverse Effects

Regulatory LimitsRadiation Worker Whole Body Extremities Skin and other organs Lens of the eyeNon-Radiation Worker Embryo/fetus Visitors and Public

5000 mrem/year 50,000 mrem/year 50,000 mrem/year 15,000 mrem/year

500 mrem/gestation period 100 mrem/year

Radiation Protection» There are three basic principles for radiation

protection

Radiation ProtectionRadiation Protection Programs in most facilities are designed to reduce dose to the staff and not the patients.While there is some leakage radiation from the head of the x-ray machine, a vast majority of radiation dose to the staff comes from the patients, animals, or objects being radiated.

Radiation Dosimetry

Dosimetry» The most effective way for a facility to assure that the staff is not

exceeding regulatory limits is to monitor the staff with dosimeters. » These devices are sometimes referred to as film badges which comes from

a time when the dosimeters actually contained little pieces of x-ray film.

» These days, the dosimeters are more sophisticated and accurate.

Dosimetry» One dosimeter, wear it on your collar or chest pocket. If you put on a lead

apron, be sure that the dosimeter is outside in front of the lead. » Two dosimeters, wear one of them on your collar or chest pocket, and one

of them on your waist. If you put on a lead apron, make sure the collar dosimeter is outside the lead and the waist dosimeter is under the lead.

» Fetal badge, keep the dosimeter down by your waist. If you put on a lead apron, make sure the dosimeter is under the lead. You want the badge to mimic as closely as possible the dose to the fetus.

» If all else fails, look on the badge itself, and it may tell you where to place it! Look at that white dot on the figure.

Conclusion

We know that high levels of radiation are very dangerous, and all facilities that use radiation are required to monitor its employees and guarantee the public so that these dangerous levels can never be reached.

Low levels of radiation may also be dangerous, and if an x-ray hits a strand of DNA just right, there is a chance it could forma cancer, so we must treat all radiation as potentially dangerous.

Radiation workers should use the concept of ALARA (As Low As Reasonably Achievable) to reduce their and their patient’s exposure to radiation.

Decreasing the time exposed to radiation, increasing the distance from the radiation source, and using shielding to block radiation are the most effective tools to implement the ALARA concept

» Radiation is all around us in many different forms, and the human body is very used to dealing with radiation and its effects.