3Radiation BasicsRadiation (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 interactionsRadioactive material can emit particles or waves.X-ray machines emit waves of radiation.
4Radioactive MaterialRadioactive 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.
5Radioactive WavesRadioactive waves are made out of massless particles called photonsThe waves can travel at different frequenciesThe range of frequency of photon radiation is called the electromagnetic spectrum
6Ionizing RadiationRadiation 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 atomOnce the atom is ionized, it will want to interact and change other atoms. This is when radiation becomes dangerous.
7Radiation UnitsRoentgen (R) – Ionizations in air – usually used in Geiger counters or detectors (like mR/hr)Rad – Radiation Absorbed Dose – energy per unit mass in any objectRem – Radiation Equivalent Man – Dose to the human body (Rad multiplied by a quality factor)Curie or Bequerel – disintegrations – used for radioactive materialThis 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!
8Radiation DamageThe 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)
9Biological EffectsThe human body can repair itself after damage done by radiationScientists 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.
10Background RadiationMan-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.
12Radiation AmountsThe 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 lifeThere 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-ray0.4 mremWatching TV (on an older model – not flat screen)1.0 mrem per year5 hour airplane flight2.5 mremChest x-ray10 mremMammogram44 mremLiving in Denver vs. Miami50 mrem per yearCAT scan of the body1000 mrem
13Biological EffectsThere 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.
14Biological EffectsWe 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 radiationDose (mrem)EffectNo visible effects8000 – 12,000Vomiting/Nausea (1-10%)13,000 – 17,000Vomiting/Nausea (25%)18,000 – 22,000Vomiting/Nausea (50%)27,000 – 32,500Vomiting/Nausea to all exposed. 50% death in 60 days if untreated40,000 – 50,000Vomiting/Nausea to all exposed. >50% death in 60 days if untreated55,000 – 75,000Vomiting/Nausea within 4 hours. 100% death if untreated100,000Vomiting/Nausea within 1-2 hours. 100% death if untreated500,000Vomiting/Nausea within immediately. 100% death in 48 hours if untreated
15Radiation 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.
16ALARA High 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.
17Radiation 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.
18Radiation and Pregnancy Adverse EffectsDuring 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.
19Regulatory Limits Radiation Worker Whole Body Extremities Skin and other organsLens of the eyeNon-Radiation WorkerEmbryo/fetusVisitors and Public5000 mrem/year50,000 mrem/year15,000 mrem/year500 mrem/gestation period100 mrem/year
20Radiation ProtectionThere are three basic principles for radiation protectionTimeMinimize the time around the x-ray source. Less time equals less exposure.DistanceIncrease the distance. Radiation reduces by 1/(distance)2ShieldingPut appropriate material between you and the source.
21Radiation 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.
22Radiation DosimetryDosimetry devices are passive monitor equipment. They provide data as to the exposure after it has occurred.Whole body monitors are required. They must be worn between the collar and the waist external of routine clothing.Monitors are exchanged monthly. They are NOT free.Area monitors are provided for additional information.Typical exposure readings have a threshold of 5 to 10 mrem. Below 10 mrem are typically reported as zero. This does not mean that the exposure was zero.The greatest risk of acute accidental exposures occurs in manipulations of the sample to be irradiated by the direct beam in diffraction studies. Exposure rates of the order of 10,000 R/sec can exist at the tube housing port. Erythema would be produced after an exposure of only 0.03 seconds and in 0.1 seconds sever and permanent injury could occur. The fingers, of course, are the parts of the body most likely to receive these high exposures.
23DosimetryThe 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.
24DosimetryOne 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.Dosimetry devices are passive monitor equipment. They provide data as to the exposure after it has occurred.Whole body monitors are required. They must be worn between the collar and the waist external of routine clothing.Monitors are exchanged monthly. They are NOT free.Area monitors are provided for additional information.Typical exposure readings have a threshold of 5 to 10 mrem. Below 10 mrem are typically reported as zero. This does not mean that the exposure was zero.The greatest risk of acute accidental exposures occurs in manipulations of the sample to be irradiated by the direct beam in diffraction studies. Exposure rates of the order of 10,000 R/sec can exist at the tube housing port. Erythema would be produced after an exposure of only 0.03 seconds and in 0.1 seconds sever and permanent injury could occur. The fingers, of course, are the parts of the body most likely to receive these high exposures.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.
25ConclusionRadiation is all around us in many different forms, and the human body is very used to dealing with radiation and its effects.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