1. Radiation Safety Training for Medical Imaging Students
Deputy Radiation Safety Officer:
Michael “Ike” Hall, CHP, CSP
Emory University Hospital

2. Topics Fundamentals of Radiation Radiation Limits and Dosimetry
Biological Effects of Radiation
Radiation and Pregnancy
Fluoroscopy and Patient Injuries
Worker Protection

3. What 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.

4. Ionizing Radiation
Ion: 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 ions
Ionization can change molecular chemistry or break apart molecules

5. Radiation Biology in a nutshell
Ionizing radiation harms biological systems by two means:
Indirectly - Production of Free Radicals
Directly - DNA damage
Indirect action is the most prevalent mechanism for cell injury.

6. Four Possible Outcomes
Cells are undamaged by the dose
Cells are damaged, repair the damage and operate normally
Cells are damaged, repair the damage and operate abnormally
Cells die as a result of the damage
Cells are undamaged by the dose
Ionization 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 normally
Some 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 abnormally
If 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 damage
If 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.

7. Measuring Radiation
Exposure: 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

8. Measuring Radiation
Equivalent 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

9. How 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

10. How 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.

11. Background Radiation Sources

12. Terrestrial Radiation
Even the highest known levels of background radiation have not proven to increase the risk to residents.
units in mGy/year
Terrestrial radiation only

13. Radiation 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.

14. Radiation Safety Principles
Time
Distance
Shielding
Containment

15. Time
Dose is directly proportional to the time spent near radiation and radioactive materials
Minimize time near radiation producing machines and radioactive materials or patients whenever possible
Plan work activities so as to spend less time handling radioactive material

16. Distance
Inverse square law: radiation exposure is inversely proportional to the square of the distance

17. Distance
Maximize your distance from radiation-producing machines and radioactive materials or patients
Use tongs or other tools to handle radioactive sources
Move radioactive materials using a cart or portable lead “pig”

18. Shielding
Use the right kind of shielding for the radiation in question
Beta radiation: Plexiglas
Gamma and x-ray: Lead or other high-density material
Use sufficient shielding for the task

19. Shielding
Engineering controls: leaded walls, windows, movable barriers, bricks, shipping and storage containers
PPE: Lead aprons, thyroid collars, and glasses for radiation-producing equipment

20. Containment
Engineering controls: Sealed sources, syringe caps, ventilation
PPE: Disposable gloves, lab coats, isolation gowns, booties, goggles, face shields, coveralls, respirators
Routine contamination monitoring is essential to verify proper containment of radioactive materials

21. Annual Occupational Limits
5000 mrem whole body
15,000 mrem to lens of eye
50,000 mrem to extremities
Set by federal government based on advice from scientific committees

22. Are 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.

23. Other Dose Limits
Members of public limited to 100 mrem per year from licensed activities, 500 mrem per year from exposure to Nuclear Medicine therapy patients
Employees under 18 limited to 10% of permissible adult dose limit (500 mrem annually)

24. Declared Pregnant Workers
500 mrem/term limit to fetus (50 mrem/month)
Limit is extremely conservative with respect to risk
Contact supervisor and Radiation Safety Officer to declare pregnancy
Monthly fetal badge assigned

25. Who 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.

26. How 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.

27. Dosimetry Wear chest badge under lead apron on chest
Wear collar badge outside lead apron
Extremity dosimetry (rings and wrist badges) must conform to Infection Control requirements

28. Proper Care of Badges
Actually take them out of the package and wear them
Take care not to reverse chest and collar badges
Do not leave badges on your apron or in the suite
Exchange badges promptly at the beginning of each month or pay $20

29. How 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.

30. Annual Occupational Limits
5000 mrem whole body
15,000 mrem to lens of eye
50,000 mrem to extremities
Set by federal government based on advice from scientific committees

31. Other Dose Limits
Members of public limited to 100 mrem per year from licensed activities, 500 mrem per year from exposure to Nuclear Medicine therapy patients
Employees under 18 limited to 10% of permissible adult dose limit (500 mrem annually)

32. Dosimetry Reports
Dosimetry reports provided monthly to departmental contact
Emory maintains permanent record, department maintains for 3 years
Review and initial dosimetry reports
Report dosimetry problems to supervisor or Radiation Safety Officer

33. So, how do I read one of these things?

34. Your 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.

35. The 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.

36. The first number is the deep dose, the dose to the whole body from penetrating radiation (1 cm tissue depth)

37. The 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)

38. The 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)

39. The report also has quarterly, annual, and lifetime accumulated totals.

40. Dose Determination
For workers with chest and collar badges, assigned dose is a combination of readings:
Whole body dose from a combination of chest and collar badges
Eye dose from lens-equivalent area of collar badge
Shallow dose from skin-equivalent area of collar badge

41. Quarterly ALARA Reports
Workers exceeding the doses on the following table are added to the ALARA report
ALARA Level 2 doses are investigated by the Radiation Safety Officer
Work activity may be restricted if corrective actions not taken

42. Quarterly ALARA Levels
Dose
Level 1
Level 2
Whole Body
 125 mrem
 375 mrem
Collar
 400 mrem
 1200 mrem
Lens of Eye
 1125 mrem
Skin
 1250 mrem
 3750 mrem
Extremities

43. What 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 sources
Laboratory and manufacturing accidents
Intentional and accidental high medical doses
Radiation controls are in place to ensure that these kinds of exposures do not happen!

44. Category of Effects
Deterministic effects occur with acute doses and result from cell death
Characterized by threshold dose (below a given dose, no effect)
Stochastic effects may occur at chronic doses
Affects the probability of all-or-none phenomena such as carcinogenesis
Ill-defined threshold dose

45. Acute Radiation Syndrome
Follows a predictable course over a period of time
Characterized by the development of signs and symptoms
Onset time of symptoms indicates dose
Severity of effect increases as dose increases

46. ARS Syndromes Bone marrow syndrome (a.k.a. hematopoietic syndrome)
Full syndrome: between 0.7 and 10 Gy
Milder symptoms may occur as low as 0.3 Gy
Gastrointestinal (GI) syndrome
Full syndrome: >10 Gy
Milder symptoms may occur as low as 6 Gy
Cardiovascular (CV)/ Central Nervous System (CNS) syndrome
Full syndrome: >50 Gy
Some symptoms may occur as low as 20 Gy

47. Bone marrow syndrome
The survival rate of patients decreases with increasing dose
Characterized 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

48. Gastrointestinal (GI) syndrome
Survival is extremely unlikely with this syndrome
Destructive and irreparable changes in the GI tract and bone marrow usually cause infection, dehydration, and electrolyte imbalance
Death usually occurs within 2 weeks

49. Cardiovascular (CV) / Central Nervous System (CNS) syndrome
Death typically occurs within 3 days
Death 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.

50. Four Stages of ARS
Prodromal 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.

51. Four Stages of ARS
Manifest 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.

52. Effects on Embryo / Fetus
High acute doses may cause death or abnormalities
Large doses between 4 – 11 weeks can cause severe abnormalities
Doses as low as 25 rad may cause defects
Doses less than 10 rad generally considered not to increase risk
According 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 defects
An exposure of 400 – 600 rad during the first trimester of pregnancy is sufficient to cause fetal death and spontaneous abortion.

53. Patients and Pregnancy
Mandatory patient pregnancy testing for high dose procedures
Screening permitted for low dose diagnostic procedures
Report cases of fetal exposure to supervisor and Radiation Safety Officer IMMEDIATELY
RSO will determine fetal dose and report to patient’s physician
According 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 defects
An exposure of 400 – 600 rad during the first trimester of pregnancy is sufficient to cause fetal death and spontaneous abortion.

54. Cutaneous 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.

55. Cutaneous Radiation Syndrome (CRS)
Cause of syndrome is radiation damage to basal cell layer of the skin
Characterized by inflammation, erythema, epilation, and/or dry or moist desquamation
Within a few hours after irradiation, a transient and inconsistent erythema (associated with itching) can occur
A 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

56. Cutaneous 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.

57. How much radiation does it take to injure skin?
SKIN EFFECT
Single-Dose Threshold (Gy)
Onset
Early transient erythema 2
Hours
Main Erythema 6
~10 d
Temporary epilation 3
~3 wk
Permanent epilation 7
Dry desquamation 14
~4 wk
Moist desquamation 18
Secondary ulceration 24
>6 wk
Late erythema 15
~6 – 10 wk
Ischemic dermal necrosis
>10 wk
Dermal atrophy (1st phase) 10
>14 wk
Dermal atrophy (2nd phase)
>1 yr
Induration (Invasive Fibrosis)
Telangiectasia
This 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)

58. 4 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 months
22 months

59. Several months after third angioplasty

60. At 3 wks At 6.5 mos Surgical flap
Ensure limbs are out of beam
At 3 wks
At 6.5 mos
Surgical flap
Following ablation procedure with arm in beam near port and separator cone removed. About 20 minutes of fluoroscopy.

61. Stochastic Effects
The 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.

62. Stochastic Effects
To 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.

63. Stochastic Effects
This 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.

64. Estimated Days of Life Expectancy Lost From Various Risk Factors
Industry Type or Activity
Estimated Days of Life Expectancy Lost
Smoking 20 cigarettes a day
2370 (6.5 years)
Overweight by 20%
985 (2.7 years)
Mining and Quarrying
328
Construction
302
Agriculture
277
Government 55
Manufacturing 43
Radiation mrem/yr for 30 years 49
Radiation mrem/yr for 70 years 34

65. Ionizing Radiation at EUH
Radiography
Fluoroscopy
Computed Tomography (CT)
Nuclear Medicine
Diagnostic
Therapeutic
Radiation Oncology
Blood Irradiation

66. How are X-rays produced?
Electrons are fired at a target made of a heavy material, like tungsten
The electrons are slowed down by the nuclei of the tungsten atoms
Some of the electron energy is converted to electromagnetic radiation (x-rays)

67. X-rays High Voltage Supply electrons Filament Current Glass envelope
Tube housing and collimator
Tungsten
filament
Target

68. Diagnostic X-ray Techniques
Radiographs
Fluoroscopy
Computed Tomography (CT)

69. How do I reduce my exposure?
Observe the following precautions:
Maximize your distance from radiation producing machines whenever practical
Do not be in the suite longer than necessary
Utilize available shielding
According 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 defects
An exposure of 400 – 600 rad during the first trimester of pregnancy is sufficient to cause fetal death and spontaneous abortion.

70. Use Available Shielding
Leaded Goggles, if necessary
Thyroid Shield
Badges
Lead vest & apron
Wear 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.

71. Use Available Shielding
Adjustable head/neck shields
RADPAD patient drapes
Leaded acrylic barriers and windows
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.
Collimate the beam to the region of interest. Use of the collimator will reduce scatter and improve image quality.

72. Distance 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/hr
20cm from scattering object
30 cm
40 cm
50 cm
1 m

73. Keep 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.

74. Collimate 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.

75. Keep 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.

76. Reduce Magnification when possible
Magnification – Almost always increases patient skin dose. Doses to personnel may also increase.

77. Be 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.

78. Thick Oblique vs Thin PA geometry
100 cm
50 cm
Dose rate:
~250 mGyt/min
40 cm
Dose rate:
20 – 40 mGyt/min
80 cm
100 cm

79. Operator’s Responsibilities
Notifying the RSO when there is a new machine or any change in setup
Keeping exposures to himself & staff ALARA
Clearing the area of all nonessential personnel

80. Operator’s Responsibilities
Observing any restrictions
Using minimum exposure factors
Notifying your supervisor and the RSO immediately of any accidental exposure to radiation

81. FDA Recommendations Establish standard procedures and protocols
Determine dose rates for specific systems
Assess each protocol for the potential for radiation injury to the patient
Modify protocols to minimize cumulative absorbed dose to any skin area
Appropriate training for all operators
On September 30, 1994 the FDA issued a Public Health Advisory with suggested actions.

82. After the Procedure
Record fluoro time and projection in patient chart, especially for interventional procedures with more than 30 minutes of beam-on time
Indicate in which room procedure occurred
Record any additional information on radiation output