Transcript Radiation Safety Training for Radiologic Technologists

Radiation Safety Training for
Medical Imaging Students
Deputy Radiation Safety Officer:
Michael “Ike” Hall, CHP, CSP
Emory University Hospital
404-712-7867
Topics
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Fundamentals of Radiation
Radiation Limits and Dosimetry
Biological Effects of Radiation
Radiation and Pregnancy
Fluoroscopy and Patient Injuries
Worker Protection
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.
Ionizing Radiation
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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
Radiation Biology
in a nutshell
Ionizing radiation harms
biological systems by two
means:
 Indirectly - Production
of Free Radicals
 Directly - DNA damage
Four Possible Outcomes
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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
Measuring Radiation
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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
Measuring Radiation
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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
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
How much radiation is in the
environment?
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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.
Background Radiation Sources
1%
15%
Radon (198 millirem)
2%
Cosmic, terrestrial, internal (97
millirem)
Consumer products (7 millirem)
55%
Medical (54 millirem)
27%
Other (4 millirem)
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
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.
Radiation Safety Principles
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Time
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Distance
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Shielding
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Containment
Time
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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
Distance
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Inverse square law: radiation exposure is
inversely proportional to the square of the
distance
Distance
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Maximize your distance from radiationproducing 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”
Shielding
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Use the right kind of shielding for the
radiation in question
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Beta radiation: Plexiglas
Gamma and x-ray: Lead or other high-density
material
Use sufficient shielding for the task
Shielding
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Engineering controls: leaded walls,
windows, movable barriers, bricks,
shipping and storage containers
PPE: Lead aprons, thyroid collars, and
glasses for radiation-producing equipment
Containment
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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
Annual Occupational Limits
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5000 mrem whole body
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15,000 mrem to lens of eye
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50,000 mrem to extremities
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Set by federal government based on
advice from scientific committees
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.
Other Dose Limits
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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)
Declared Pregnant Workers
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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
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.
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.
Dosimetry
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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
Proper Care of Badges
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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
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.
Annual Occupational Limits
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5000 mrem whole body
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15,000 mrem to lens of eye
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50,000 mrem to extremities
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Set by federal government based on
advice from scientific committees
Other Dose Limits
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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)
Dosimetry Reports
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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
So, how do I read one of these things?
Your name and participant number are
listed in the first column. The date of the
badges on the report is shown above.
The badge types on the report are listed
here. Most Radiology workers have chest
and collar badges.
The first number is the deep dose, the dose
to the whole body from penetrating
radiation (1 cm tissue depth)
The next number is the eye dose, the dose
to the lens of the eye (0.3 cm tissue depth)
The last number is the shallow dose, the
dose to the dermal layer (0.007 cm tissue
depth)
The report also has quarterly, annual, and
lifetime accumulated totals.
Dose Determination
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For workers with chest and collar
badges, assigned dose is a combination
of readings:
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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
Quarterly ALARA Reports
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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
Quarterly ALARA Levels
Dose
Level 1
Level 2
Whole Body
 125 mrem
 375 mrem
Collar
 400 mrem
 1200 mrem
Lens of Eye
 375 mrem
 1125 mrem
Skin
 1250 mrem
 3750 mrem
Extremities
 1250 mrem
 3750 mrem
What are the effects of high doses
of radiation?
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Acute radiation exposure, however rare, may
result in severe clinical effects or even death:
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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!
Category of Effects
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Deterministic effects occur with acute doses
and result from cell death
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Characterized by threshold dose (below a given dose,
no effect)
Stochastic effects may occur at chronic doses
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Affects the probability of all-or-none phenomena such
as carcinogenesis
Ill-defined threshold dose
Acute Radiation Syndrome
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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
ARS Syndromes
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Bone marrow syndrome (a.k.a. hematopoietic
syndrome)
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Gastrointestinal (GI) syndrome
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Full syndrome: between 0.7 and 10 Gy
Milder symptoms may occur as low as 0.3 Gy
Full syndrome: >10 Gy
Milder symptoms may occur as low as 6 Gy
Cardiovascular (CV)/ Central Nervous System
(CNS) syndrome
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Full syndrome: >50 Gy
Some symptoms may occur as low as 20 Gy
Bone marrow syndrome
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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
Gastrointestinal (GI) syndrome
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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
Cardiovascular (CV) / Central
Nervous System (CNS) syndrome
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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.
Four Stages of ARS
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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.
Four Stages of ARS
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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.
Effects on Embryo / Fetus
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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
Patients and Pregnancy
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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
Cutaneous Radiation Syndrome
(CRS)
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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.
Cutaneous Radiation Syndrome
(CRS)
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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
Cutaneous Radiation Syndrome
(CRS)
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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.
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
~3 wk
Dry desquamation
14
~4 wk
Moist desquamation
18
~4 wk
Secondary ulceration
24
>6 wk
Late erythema
15
~6 – 10 wk
Ischemic dermal necrosis
18
>10 wk
Dermal atrophy (1st phase)
10
>14 wk
Dermal atrophy (2nd phase)
10
>1 yr
Induration (Invasive Fibrosis)
10
>1 yr
Telangiectasia
10
>1 yr
d: day(s); wk: week(s); yr: year(s)
4 months after
procedures
22 months
7 months
23 months
9 months
Three TIPS procedures in 1 week in type II
diabetic. Total procedure time 13 - 16
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!
Several months
after third
angioplasty
5 months
22 months
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.
Stochastic Effects
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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.
Stochastic Effects
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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.
Stochastic Effects
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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.
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 - 340 mrem/yr for 30 years
49
Radiation - 100 mrem/yr for 70 years
34
Ionizing Radiation at EUH
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Radiography
Fluoroscopy
Computed Tomography (CT)
Nuclear Medicine
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Diagnostic
Therapeutic
Radiation Oncology
Blood Irradiation
How are X-rays produced?
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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)
High Voltage
Supply
Glass envelope
Tube housing and collimator
Tungsten
Target
electrons
X-rays
Tungsten
filament
Filament
Current
Supply
Diagnostic X-ray Techniques
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Radiographs
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Fluoroscopy
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Computed Tomography (CT)
How do I reduce my exposure?
Observe the following precautions:
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Maximize your distance from radiation
producing machines whenever practical
Do not be in the suite longer than
necessary
Utilize available shielding
Use Available Shielding
Leaded Goggles, if
necessary
Thyroid Shield
Badges
Lead vest & apron
Wear dosimetry!
Use Available Shielding
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Adjustable head/neck
shields
RADPAD patient
drapes
Leaded acrylic
barriers and windows
Distance
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Know room geometry
NEVER PUT UNPROTECTED HANDS IN
BEAM
72 mR/hr
21 mR/hr
(1)
(2)
(3)
(4)
106 mR/hr
32 mR/hr
1.
2.
3.
4.
5.
(5)
3 mR/hr
20cm from scattering object
30 cm
40 cm
50 cm
1m
Keep Image Intensifier Close to
Patient
Collimate to the Area of
Interest
Don’t catch the edge of
the patient.
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.
Reduce Magnification when
possible
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.
Thick Oblique vs Thin PA geometry
100 cm
40 cm
Dose rate:
20 – 40 mGyt/min
80 cm
Dose rate:
~250 mGyt/min
100 cm
50 cm
Operator’s Responsibilities
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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
Operator’s Responsibilities
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Observing any restrictions
Using minimum exposure factors
Notifying your supervisor and the RSO
immediately of any accidental exposure to
radiation
FDA Recommendations
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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
After the Procedure
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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