Presentation on theme: "Radiation Safety Training for Medical Imaging Students"— Presentation transcript:
1Radiation Safety Training for Medical Imaging Students Deputy Radiation Safety Officer:Michael “Ike” Hall, CHP, CSPEmory University Hospital
2Topics Fundamentals of Radiation Radiation Limits and Dosimetry Biological Effects of RadiationRadiation and PregnancyFluoroscopy and Patient InjuriesWorker Protection
3What is radiation?Radiation is energy emitted from unstable atoms. Radiation can be in the form of subatomic particles (alpha or beta particles) or electromagnetic radiation (X and gamma rays). Radiation that is energetic enough to change the chemistry of a target is called ionizing radiation, and that will be the focus of this training.
4Ionizing RadiationIon: atom with a positive or negative charge (i.e., too few or too many electrons)Radiation that is energetic enough can strip electrons and create ionsIonization can change molecular chemistry or break apart molecules
5Radiation Biology in a nutshell Ionizing radiation harms biological systems by two means:Indirectly - Production of Free RadicalsDirectly - DNA damageIndirect action is the most prevalent mechanism for cell injury.
6Four Possible Outcomes Cells are undamaged by the doseCells are damaged, repair the damage and operate normallyCells are damaged, repair the damage and operate abnormallyCells die as a result of the damageCells are undamaged by the doseIonization may form chemically active substances which in some cases alter the structure of the cells. These alterations may be the same as those changes that occur naturally in the cell and may have no negative effect.Cells are damaged, repair the damage and operate normallySome ionizing events produce substances not normally found in the cell. These can lead to a breakdown of the cell structure and its components. Cells can repair the damage if it is limited. Even damage to the chromosomes is usually repaired. Many thousands of chromosome aberrations (changes) occur constantly in our bodies. We have effective mechanisms to repair these changes.Cells are damaged, repair the damage and operate abnormallyIf a damaged cell needs to perform a function before it has had time to repair itself, it will either be unable to perform the repair function or perform the function incorrectly or incompletely. The result may be cells that cannot perform their normal functions or that now are damaging to other cells. These altered cells may be unable to reproduce themselves or may reproduce at an uncontrolled rate. Such cells can be the underlying causes of cancers.Cells die as a result of the damageIf a cell is extensively damaged by radiation, or damaged in such a way that reproduction is affected, the cell may die. Radiation damage to cells may depend on how sensitive the cells are to radiation.
7Measuring RadiationExposure: measure of ionization in air (roentgen, or R)Absorbed dose: energy deposited in material per unit mass (Gray or rad)1 Gray = 1 Joule/kg = 100 rad
8Measuring RadiationEquivalent dose: measure of the biological effect of a specific kind of radiation on humans (Sieverts or rem)For x-rays, dose and dose equivalent are equal. Dose equivalence may be different for some radioactive particles.1 Gray = 1 Sievert = 100 rem
9How much radiation is harmful? Radiogenic health effects (primarily cancer) are observed in humans only at doses in excess of 10 rem delivered at high dose rates. Below this dose, estimation of adverse health effect is speculative.“Radiation Risk in Perspective”Health Physics Society
10How much radiation is in the environment? People are exposed to background radiation continuously.The average dose due to background exposure is around 350 millirem per year in the United States.Background exposure can vary with altitude, soil, and medical usage.
12Terrestrial Radiation Even the highest known levels of background radiation have not proven to increase the risk to residents.units in mGy/yearTerrestrial radiation only
13Radiation Safety Principles The Radiation Safety program, including training, monitoring, and contamination control, is designed to ensure that no worker receives a radiation dose in excess of regulatory limits, and that each worker generally receives only as much exposure as necessary to do one's job.
15TimeDose is directly proportional to the time spent near radiation and radioactive materialsMinimize time near radiation producing machines and radioactive materials or patients whenever possiblePlan work activities so as to spend less time handling radioactive material
16DistanceInverse square law: radiation exposure is inversely proportional to the square of the distance
17DistanceMaximize your distance from radiation-producing machines and radioactive materials or patientsUse tongs or other tools to handle radioactive sourcesMove radioactive materials using a cart or portable lead “pig”
18ShieldingUse the right kind of shielding for the radiation in questionBeta radiation: PlexiglasGamma and x-ray: Lead or other high-density materialUse sufficient shielding for the task
19ShieldingEngineering controls: leaded walls, windows, movable barriers, bricks, shipping and storage containersPPE: Lead aprons, thyroid collars, and glasses for radiation-producing equipment
20ContainmentEngineering controls: Sealed sources, syringe caps, ventilationPPE: Disposable gloves, lab coats, isolation gowns, booties, goggles, face shields, coveralls, respiratorsRoutine contamination monitoring is essential to verify proper containment of radioactive materials
21Annual Occupational Limits 5000 mrem whole body15,000 mrem to lens of eye50,000 mrem to extremitiesSet by federal government based on advice from scientific committees
22Are these limits safe?The annual radiation limits have been established to ensure that the long-term risks of radiation exposure are minimized. There has been no evidence that occupational doses within these limits pose any risk. Due to potential uncertainties in dose measurement, the limits are set conservatively.
23Other Dose LimitsMembers of public limited to 100 mrem per year from licensed activities, 500 mrem per year from exposure to Nuclear Medicine therapy patientsEmployees under 18 limited to 10% of permissible adult dose limit (500 mrem annually)
24Declared Pregnant Workers 500 mrem/term limit to fetus (50 mrem/month)Limit is extremely conservative with respect to riskContact supervisor and Radiation Safety Officer to declare pregnancyMonthly fetal badge assigned
25Who gets radiation badges? Radiation badges are required for workers who are likely to receive more than 10% of the annual occupational radiation limits.In practice, almost everyone who routinely works with radioactive materials or radiation-producing machines gets one or more badges.
26How do I request a badge?Ask your supervisor or the Radiation Safety Officer for a Personnel History Form. You may also find the form online.Radiation Safety Training is required to get a badge. Please ask your supervisor or the RSO. Training may be provided as an orientation packet, an inservice, or online.
27Dosimetry Wear chest badge under lead apron on chest Wear collar badge outside lead apronExtremity dosimetry (rings and wrist badges) must conform to Infection Control requirements
28Proper Care of BadgesActually take them out of the package and wear themTake care not to reverse chest and collar badgesDo not leave badges on your apron or in the suiteExchange badges promptly at the beginning of each month or pay $20
29How does the badge work?The Luxel dosimeter has a thin strip of specially formulated aluminum oxide (Al2O3) crystalline material. Filters of various thickness simulate radiation doses to different tissues. During analysis, the strip is stimulated with laser light, causing it to luminesce in proportion to the amount of radiation exposure.
30Annual Occupational Limits 5000 mrem whole body15,000 mrem to lens of eye50,000 mrem to extremitiesSet by federal government based on advice from scientific committees
31Other Dose LimitsMembers of public limited to 100 mrem per year from licensed activities, 500 mrem per year from exposure to Nuclear Medicine therapy patientsEmployees under 18 limited to 10% of permissible adult dose limit (500 mrem annually)
32Dosimetry ReportsDosimetry reports provided monthly to departmental contactEmory maintains permanent record, department maintains for 3 yearsReview and initial dosimetry reportsReport dosimetry problems to supervisor or Radiation Safety Officer
34Your name and participant number are listed in the first column Your name and participant number are listed in the first column. The date of the badges on the report is shown above.
35The badge types on the report are listed here The badge types on the report are listed here. Most Radiology workers have chest and collar badges.
36The first number is the deep dose, the dose to the whole body from penetrating radiation (1 cm tissue depth)
37The next number is the eye dose, the dose to the lens of the eye (0 The next number is the eye dose, the dose to the lens of the eye (0.3 cm tissue depth)
38The last number is the shallow dose, the dose to the dermal layer (0 The last number is the shallow dose, the dose to the dermal layer (0.007 cm tissue depth)
39The report also has quarterly, annual, and lifetime accumulated totals.
40Dose DeterminationFor workers with chest and collar badges, assigned dose is a combination of readings:Whole body dose from a combination of chest and collar badgesEye dose from lens-equivalent area of collar badgeShallow dose from skin-equivalent area of collar badge
41Quarterly ALARA Reports Workers exceeding the doses on the following table are added to the ALARA reportALARA Level 2 doses are investigated by the Radiation Safety OfficerWork activity may be restricted if corrective actions not taken
43What are the effects of high doses of radiation? Acute radiation exposure, however rare, may result in severe clinical effects or even death:Exposures of minutes to hours while handling highly radioactive sourcesLaboratory and manufacturing accidentsIntentional and accidental high medical dosesRadiation controls are in place to ensure that these kinds of exposures do not happen!
44Category of EffectsDeterministic effects occur with acute doses and result from cell deathCharacterized by threshold dose (below a given dose, no effect)Stochastic effects may occur at chronic dosesAffects the probability of all-or-none phenomena such as carcinogenesisIll-defined threshold dose
45Acute Radiation Syndrome Follows a predictable course over a period of timeCharacterized by the development of signs and symptomsOnset time of symptoms indicates doseSeverity of effect increases as dose increases
46ARS Syndromes Bone marrow syndrome (a.k.a. hematopoietic syndrome) Full syndrome: between 0.7 and 10 GyMilder symptoms may occur as low as 0.3 GyGastrointestinal (GI) syndromeFull syndrome: >10 GyMilder symptoms may occur as low as 6 GyCardiovascular (CV)/ Central Nervous System (CNS) syndromeFull syndrome: >50 GySome symptoms may occur as low as 20 Gy
47Bone marrow syndromeThe survival rate of patients decreases with increasing doseCharacterized by damage to cells that divide at the most rapid pace (such as bone marrow, the spleen and lymphatic tissue)The primary cause of death is the destruction of the bone marrow, resulting in infection and hemorrhage
48Gastrointestinal (GI) syndrome Survival is extremely unlikely with this syndromeDestructive and irreparable changes in the GI tract and bone marrow usually cause infection, dehydration, and electrolyte imbalanceDeath usually occurs within 2 weeks
49Cardiovascular (CV) / Central Nervous System (CNS) syndrome Death typically occurs within 3 daysDeath likely is due to collapse of the circulatory system as well as increased pressure in the confining cranial vault as the result of increased fluid content caused by edema, vasculitis, and meningitis.
50Four Stages of ARSProdromal stage (N-V-D stage): Classic symptoms are nausea, vomiting, as well as anorexia and possibly diarrhea, which occur from minutes to days following exposure. The symptoms may last (episodically) for minutes up to several days.Latent stage: Patient looks and feels generally healthy for a few hours or even up to a few weeks.
51Four Stages of ARSManifest illness stage: Symptoms depend on the specific syndrome and last from hours up to several months.Recovery or death: Most patients who do not recover will die within several months of exposure. The recovery process lasts from several weeks up to two years.
52Effects on Embryo / Fetus High acute doses may cause death or abnormalitiesLarge doses between 4 – 11 weeks can cause severe abnormalitiesDoses as low as 25 rad may cause defectsDoses less than 10 rad generally considered not to increase riskAccording to the law of Bergonie and Tribondeau children are more radiosensitive than adults, fetuses more than children and embryos are the most radiosensitive.Radiation doses may cause death or abnormalities - Effects include blindness, cataracts, mental deficiency, coordination defects, deformed arms/legs.Large doses between 4 – 11 weeks postconception can cause severe abnormalities - An organ is most susceptible to abnormalities during early organ formation. Prior to and after these stages major abnormalities in that organ are not likely to result.Doses as low as 25 rad may cause defectsAn exposure of 400 – 600 rad during the first trimester of pregnancy is sufficient to cause fetal death and spontaneous abortion.
53Patients and Pregnancy Mandatory patient pregnancy testing for high dose proceduresScreening permitted for low dose diagnostic proceduresReport cases of fetal exposure to supervisor and Radiation Safety Officer IMMEDIATELYRSO will determine fetal dose and report to patient’s physicianAccording to the law of Bergonie and Tribondeau children are more radiosensitive than adults, fetuses more than children and embryos are the most radiosensitive.Radiation doses may cause death or abnormalities - Effects include blindness, cataracts, mental deficiency, coordination defects, deformed arms/legs.Large doses between 4 – 11 weeks postconception can cause severe abnormalities - An organ is most susceptible to abnormalities during early organ formation. Prior to and after these stages major abnormalities in that organ are not likely to result.Doses as low as 25 rad may cause defectsAn exposure of 400 – 600 rad during the first trimester of pregnancy is sufficient to cause fetal death and spontaneous abortion.
54Cutaneous Radiation Syndrome (CRS) Recently introduced to describe the complex pathological syndrome that results from acute radiation exposure to the skin.It is possible to receive a damaging dose to the skin without symptoms of ARS, especially with acute exposures to beta radiation or X-rays.
55Cutaneous Radiation Syndrome (CRS) Cause of syndrome is radiation damage to basal cell layer of the skinCharacterized by inflammation, erythema, epilation, and/or dry or moist desquamationWithin a few hours after irradiation, a transient and inconsistent erythema (associated with itching) can occurA latent phase may occur and last from a few days up to several weeks, when intense reddening, blistering, and ulceration of the irradiated site are visible
56Cutaneous Radiation Syndrome (CRS) In most cases, healing occurs by regenerative means; however, very large skin doses can cause permanent hair loss, damaged sebaceous and sweat glands, atrophy, fibrosis, decreased or increased skin pigmentation, and ulceration or necrosis of the exposed tissue.
57How much radiation does it take to injure skin? SKIN EFFECTSingle-Dose Threshold (Gy)OnsetEarly transient erythema2HoursMain Erythema6~10 dTemporary epilation3~3 wkPermanent epilation7Dry desquamation14~4 wkMoist desquamation18Secondary ulceration24>6 wkLate erythema15~6 – 10 wkIschemic dermal necrosis>10 wkDermal atrophy (1st phase)10>14 wkDermal atrophy (2nd phase)>1 yrInduration (Invasive Fibrosis)TelangiectasiaThis table lists the Threshold skin entrance doses for different skin injuries (Data adopted from Wagner, Eifel and Geise, 1994 and modified on data from John Hopewell, oral communication, 1999).d: day(s); wk: week(s); yr: year(s)
584 months after procedures An example of a patient injury, and how it was misdiagnosed and then diagnosed.Three TIPS procedures in 1 week in type II diabetic. Total procedure time hours. Three weeks later noticed 13-cm x 17-cm mottled oval discoloration on back. Initially diagnosed as strep infection, then as herpes I, then as allergic reaction to oral diabetic medications. Diagnosis of radiodermatitis obtained ten months after procedure!23 months22 months
60At 3 wks At 6.5 mos Surgical flap Ensure limbs are out of beamAt 3 wksAt 6.5 mosSurgical flapFollowing ablation procedure with arm in beam near port and separator cone removed. About 20 minutes of fluoroscopy.
61Stochastic EffectsThe effects of low levels of radiation are more difficult to determine because the deterministic effects described above do not occur at these levels.Studies of people who have received high doses have shown a link between radiation dose and some delayed, or latent effects, including some forms of cancer and genetic effects.
62Stochastic EffectsTo estimate the risks associated with low or chronic exposure, we create a model of the risk of occurrence of cancer at high doses to the risk of cancer at low doses, usually assuming no threshold. This type of risk model is called stochastic. The risk of a clinical effect increases with the dose, but the effect is the same.
63Stochastic EffectsThis scaling or extrapolation is generally considered to be a conservative approach (may over-estimate the risk) to estimating low-dose risks.The risk of certain effects, including cancer, may be cumulative in patients with repeated examinations and higher in younger patients.
64Estimated Days of Life Expectancy Lost From Various Risk Factors Industry Type or ActivityEstimated Days of Life Expectancy LostSmoking 20 cigarettes a day2370 (6.5 years)Overweight by 20%985 (2.7 years)Mining and Quarrying328Construction302Agriculture277Government55Manufacturing43Radiation mrem/yr for 30 years49Radiation mrem/yr for 70 years34
65Ionizing Radiation at EUH RadiographyFluoroscopyComputed Tomography (CT)Nuclear MedicineDiagnosticTherapeuticRadiation OncologyBlood Irradiation
66How are X-rays produced? Electrons are fired at a target made of a heavy material, like tungstenThe electrons are slowed down by the nuclei of the tungsten atomsSome of the electron energy is converted to electromagnetic radiation (x-rays)
67X-rays High Voltage Supply electrons Filament Current Glass envelope Tube housing and collimatorTungstenfilamentTarget
69How do I reduce my exposure? Observe the following precautions:Maximize your distance from radiation producing machines whenever practicalDo not be in the suite longer than necessaryUtilize available shieldingAccording to the law of Bergonie and Tribondeau children are more radiosensitive than adults, fetuses more than children and embryos are the most radiosensitive.Radiation doses may cause death or abnormalities - Effects include blindness, cataracts, mental deficiency, coordination defects, deformed arms/legs.Large doses between 4 – 11 weeks postconception can cause severe abnormalities - An organ is most susceptible to abnormalities during early organ formation. Prior to and after these stages major abnormalities in that organ are not likely to result.Doses as low as 25 rad may cause defectsAn exposure of 400 – 600 rad during the first trimester of pregnancy is sufficient to cause fetal death and spontaneous abortion.
70Use Available Shielding Leaded Goggles, if necessaryThyroid ShieldBadgesLead vest & apronWear dosimetry!Personnel protection – If not positioned behind a barrier a lead apron must be worn. Aprons should be properly stored and checked for cracks and holes annually. Wear personnel dosimeters on the collar outside of the lead apron. Use distance and take advantage of the inverse square law. Eye wear and thyroid shields are recommended if the monthly collar dose exceeds 400 mrem. Lower extremity shields can be used to shield the feet and legs. Hands may be protected by the use of hand shields, or xray attenuating surgical gloves. But, don’t be lured into a false sense of security and continue to make sure hands are out of the beam as much as possible. Wear ring dosimeters on the dominant hand to measure hand exposure. Use an additional dosimeter under the lead apron for pregnant personnel.
71Use Available Shielding Adjustable head/neck shieldsRADPAD patient drapesLeaded acrylic barriers and windowsPersonnel protection – If not positioned behind a barrier a lead apron must be worn. Aprons should be properly stored and checked for cracks and holes annually. Wear personnel dosimeters on the collar outside of the lead apron. Use distance and take advantage of the inverse square law. Eye wear and thyroid shields are recommended if the monthly collar dose exceeds 400 mrem. Lower extremity shields can be used to shield the feet and legs. Hands may be protected by the use of hand shields, or xray attenuating surgical gloves. But, don’t be lured into a false sense of security and continue to make sure hands are out of the beam as much as possible. Wear ring dosimeters on the dominant hand to measure hand exposure. Use an additional dosimeter under the lead apron for pregnant personnel.Collimate the beam to the region of interest. Use of the collimator will reduce scatter and improve image quality.
72Distance Know room geometry NEVER PUT UNPROTECTED HANDS IN BEAM 72 mR/hr mR/hr(1) (2) (3) (4) (5)106 mR/hr mR/hr mR/hr20cm from scattering object30 cm40 cm50 cm1 m
73Keep Image Intensifier Close to Patient Keep patient at maximum distance from x-ray tube – x-ray intensity is reduced as distance is increased. Watch for extremities that may be close to the direct beam. For diagnostic procedures make sure that the separator cone is attached to the x-ray tube.Image Intensifier distance – The image intensifier should be as close to the patient as possible to reduce entrance skin dose. If it is a machine where the II and tube can be moved independently when the II is closer to the patient the production of x-rays will decrease since the distance is shorter. The best configuration is to keep the x-ray tube under the patient.
74Collimate to the Area of Interest Collimate the beam to the region of interest. Use of the collimator will reduce scatter and improve image quality.Don’t catch the edge of the patient.
75Keep X-Ray Tube Below Patient The patient is the source of the scattered radiation in the x-ray suite.The spacer provides a minimum safe distance to the patient’s skin from the x-ray tube.
76Reduce Magnification when possible Magnification – Almost always increases patient skin dose. Doses to personnel may also increase.
77Be Aware of Patient Thickness When using automatic brightness, larger patients will have a higher radiation exposure for the same image quality as a thinner patient. Avoid oblique angles when possible.Tube Current (mA) / kVp – Keep the kVp as high as possible and the mA as low as possible to obtain a good compromise between image quality and low patient dose. An increase in mA will increase patient and personnel dose.
78Thick Oblique vs Thin PA geometry 100 cm50 cmDose rate:~250 mGyt/min40 cmDose rate:20 – 40 mGyt/min80 cm100 cm
79Operator’s Responsibilities Notifying the RSO when there is a new machine or any change in setupKeeping exposures to himself & staff ALARAClearing the area of all nonessential personnel
80Operator’s Responsibilities Observing any restrictionsUsing minimum exposure factorsNotifying your supervisor and the RSO immediately of any accidental exposure to radiation
81FDA Recommendations Establish standard procedures and protocols Determine dose rates for specific systemsAssess each protocol for the potential for radiation injury to the patientModify protocols to minimize cumulative absorbed dose to any skin areaAppropriate training for all operatorsOn September 30, 1994 the FDA issued a Public Health Advisory with suggested actions.
82After the ProcedureRecord fluoro time and projection in patient chart, especially for interventional procedures with more than 30 minutes of beam-on timeIndicate in which room procedure occurredRecord any additional information on radiation output