Radiation Safety Flashcards
Roentgen: in air
RAD: Absorbed Dose
=Roentgen X tissue weighting factor (f), which is approx 1 for human tissue
1 GRAY = 100 Rad
REM: Equivalent Man (dose equivalent, effective dose)
=RAD X quality factor (QF), which is based on LET of individual particle used (eg gamma rays, where QF is 1)
LET: energy ABSORBED by a MEDIUM per unit length for a given particle type (keV/um)
1 SIEVERT = 100 REM
For nuclear medicine (gamma rays):
1 Roentgen = 1 RAD = 1 REM (+/-)
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BERT (background equivalent)
Annual NATURAL background (eg not incl man made): approx 300 mRem
(hps.org–Health Physics)
Tc99m MIBI study = 7 years X annual background
Cath = 9 years
CT angio = 4 years
CXR = 10 days
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Background
Air: radon
Terrestrial: uranium, radium, thorium
Cosmic: from sun and stars continuously
Internal: everyone has small amt of radioisotopes in body
Natural sources makes up approx 50% of annual background exposure
Remainder is man-made (imaging mostly)
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Non-Occupational exposure, from Occupational sources (testing)
Limit: 100 mRem/year
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Non-Occ exposure from family member from one-time procedure (eg pt goes home after MIBI)–ie release criteria from nuclear lab
limit: 500 mRem (at once)
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Occ worker dose limits
Whole body (OSL badge): 5 Rem/year
Skin or extremity (TLD ring badge): 50 Rem/year
Lens of eye: 15 Rem/year
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Quarterly Occ worker dose limits
Whole body: 125 mRem/quarter = notify, 375 mRem = investigate/take action
Extremity: 1875 mRem, 5625 mRem
Skin: 750, 2250
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Occ Worker Pregnant
(i.e. Limit to non-occ worker fetus)
Limit: 500 mRem over gestation
Monitor monthly: limit <50 mRem/month
You must modify pregnant female work if possible to limit exposure
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Personnel monitoring
Monitor any worker likely to exceed 500 mRem/year
TLD ring badge for hand (“extremity”), skin monitoring
OSL (stethoscope badge) for whole body monitor
Pocket ion chamber for monitoring visitors (must read after each use, doesn’t store info)
Frequency: monitor personnel MONTHLY
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Radiation biological effects
Stochastic (sounds like cancer): no dose threshold, i.e. probability of occurrence is never zero
But probability increases with dose
Curve is straight linear slope
Deterministic:
Zero probability until pass threshold–asymptotic curve
All non-cancer effects (sterility, cataracts, skin)
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Surveys
Daily contamination check (GM meter)
Must check <1cm from the surface you’re checking
(Limits vary by state)
Wipe tests for removable contamination (? only for packages): Must wipe 10cm X 10cm area Use well counter and scaler (?) Limits: Restricted area: 5000dpm/100cm-sq Unrestricted area: 200 dpm/100cm-sq
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Spills procedures
Major vs minor spill
Depends on the isotope, i.e. how many mCi defines major
*for Tc99m it’s > 100mCi = major
Minor spill: Notify all people in the area Cover with absorbent paper CLEAN UP Survey the area and staff for radiation LAST STEP = Report to RSO
Major spill: 1st step is CLEAR THE AREA Cover with absorbent paper SHIELD the area Close and lock room, place signs to avoid entry NOTIFY RSO Survey and decontaminate personnel Last step is CLEAN bc you need RSO guidance on how to clean
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Waste management
Decay in storage
Transfer to auth recipient
Sewage
Atmosphere
Storage decay:
Cannot discard it until meets BOTH criteria of:
(1) 10 half lives have passed (Tc = 60 hrs)
AND
(2) survey is indistinguishable from background
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To return spent or unused doses to vendor:
Must survey package AT THE SURFACE and be
<0.5mR/hr
Must wipe-test the surface: <6600 dpm/300 cm2
Total any of activity (mCi) must be below set limit as well
Labeled “limited quantity, excepted package”
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Receiving doses
Must monitor package
within 3 hrs of delivery (or start of business day)
Survey at 1 meter from package–report if >10mR/hr
Wipe test optional, only if suspect contamination
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