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X-ray Safety Training
Texas A&M Health Science CenterEnvironmental Health and Safety
Rev. 03-2015
Agenda
• Introduction– Regulatory structure– Rad safety program
• What is radiation?– Types of radiation– Biological effects of
radiation– Background radiation– Radiation detection
• HSC Procedures– Safety (PPE, storage, etc)– Survey Procedure
REGULATORY OVERSIGHT
Line of Authorization from the State
• US NRC– Delegates responsibilities
to TDSHS
• TDSHS– Issues licenses and
ensures compliance within the state
• HSC– Radiation Safety Officer
(RSO) and Radiation Committee (RSC) oversee institutional compliance
Line of Authorization at the HSC
• HSC– Holds a “Registration” for use of X-ray generating
devices our campuses– RSO and RSC• Create, review, and approve the institutional radiation
safety manual• Create review and approve new principal investigators
(PIs) to become radiation generating device permittees
EHS website
http://www.tamhsc.edu/ehs/
HSC X-ray Permit
X-RAY PRODUCTION AND BASICS
X-ray production (X-ray tube)
X-ray production - Bremsstrahlung
• Bremsstrahlung X-rays• Charged particles radiate
electromagnetic energy whenever they experience a change in velocity (either in speed or direction)
• These x-rays are emitted when high-speed charged particles undergo rapid acceleration
X-ray production – electron ejection
• Incoming electron can impart enough energy to result in an ejection of the K shell electron
• An Electron will drop into the K shell to balance energy results in the characteristic x-ray
X-ray production - characteristics
• Electron “holes” can be filled with either an L-shell or M-shell electron
• N, O, and higher shell electrons create characteristic x-rays that are lost in the noise
• Al or Be filters are used to block the x-rays of lower energy than the characteristic to “harden” the beam
X-ray basics – ionizing radiation
• Ionizing• Alpha• Beta• Gamma• X-ray
• Non-Ionizing – Microwaves – Sunlight – Infrared waves – Radio waves – Lasers
X-ray basics - shielding
• X-rays will pass through many materials
• Most often, they require lead or concrete as a shield
Radiation Penetration
UNITS & DEFINITIONS USED IN RADIATION
Units & Definitions - Exposure
Roentgen R the unit of exposure to Ionizing Radiation. The amount of γ or x-ray radiation required to produce 1.0 electrostatic unit of charge in 1.0 cubic centimeter of dry air.
Use the abbreviation “R/hr” or “mR/hr” when measuring an x-ray, gamma, or beta dose.
Units & Definitions – Absorbed Dose
RAD (radiation absorbed dose) is a unit of measurement used to describe the amount of energy transferred from a source of ionizing radiation to any material, including human tissue.
• As a unit of exposure, 1 rad means that each gram of air at 0° C and 1 atmosphere has absorbed 100 ergs of energy.
• As a unit of dose, 1 rad means that each gram of exposed tissue has abosorbed 100 ergs of energy.
• Note: The SI unit for absorbed dose is the Gray (Gy). 100 rad = 1 Gy
Units & Definitions – Dose + Risk
Different types of ionizing radiation cause differing degrees of biological effects even when the same amount of energy is transferred.
To create a universal measurement, the “rad” is multiplied by the specific quality factor for a type of ionizing radiation to determine the dose equivalent.
The rate at which an individual is exposed (i.e. an hour verses a lifetime) also influences the level of biological harm.
Use a dosimeter to measure a dose equivalent.
Units & Definitions – Quality Factor
• Used to relate the absorbed dose of various kinds of radiation to the biological damage caused to the exposed tissue
• Necessary because the same amounts absorbed of different kinds of radiation cause different degrees of damage
• Converts the absorbed dose to a unit of dose equivalence to compare damage caused by any kind of radiation
Radiation Type Quality Factor (QF)
X-rays, Gamma rays, Beta particles
1
Protons 10
Alpha particles 20
Units & Definitions – Dose Equivalent
Dose Equivalent Rem (Roentgen Equivalent Man) is the dose equivalent for tissue, and takes into account the varying amount of damage to tissue based on the energy and radiation type, and accounts for tissue sensitivity or the risk of malignancy from the radiation induced injury.
The dose equivalent can be determined by applying a tissue weighting factor (risk factor) to the absorbed dose (rad).
Use the abbreviation “Rem/hr” or “mRem/hr” when measuring an x-ray, gamma, or beta dose.
Note: The SI unit for dose is the Sievert (Sv). 100 Rem = 1 Sv
BIOLOGICAL EFFECTS OFIONIZING RADIATION
Excitation and Ionization
Excitation Ionization
Ionizing Water
Radiation Induced Decomposition of Water within a cell• H2O can form the following:
– H2O+
– H2
– H+
– H0
– OH-
– OH0
– HO2
– H2O2
– e-
• Free radicals within the cell can result in indirect effects
Harderian Wasp Eggs
Effects of ionizing radiation (DNA)
• DNA damage can result from radiation– Single and double strand breaks– Most often repaired successfully by the cell
Potential Outcomes of Radiation Damage to Parent Cells
Radiosensitivity
Law of Bergonie & Tribondeau (1906)Determinants of Radiosensitivity
Law states that radiosensitivity varies:1. Directly with rate of cell division
(more metabolically active = more radiosensitive)
2. Directly with number of future divisions a cell will undergo
(younger cells are more radiosensitive)
3. Inversely with the degree of cellular differentiation
(stems cells are the most radiosensitive)
Radiosensitive tissues
Radio-sensitive Cells Radio-resistant Cells
Reproductive Cells Bone, Cartilage, Muscle
Blood forming tissues Liver
Epithelium of skin Kidney
Epithelium of gastrointestinal tract Nerve tissue
Biological Effect Parameters:
The radiogenic biological effect depends on:
1. Radiation Type
2. Rate of Exposure / Absorption
3. Area Exposed (Variation in Cell Sensitivity)
4. Variation in Species and Individual Sensitivity
Biological Effects Sumary
• In summary, radiation may:– Interact within the body– Deposit energy in the body– Create ionizations in the body– Cause DNA damage
• All of which may lead to biological damage, but:– Damage may be repaired– Damage may be benign– Damage may be neutralized through apoptosis
RADIATION PROTECTION
ALARA
Philosophy• Radiation doses are
kept as low as possible• Stems from Linear-Non-
Threshold dose model• ALARA program
required by Federal and State regulations
Keys to ALARA
• Time• Distance• Shielding• Housekeeping
Radiation Protection Basics
The INDIVIDUAL working with radiation generating devices
MUST
assume the RESPONSIBILITY for their own safety
AND
must ensure that their actions do not result in a hazard to others.
Natural Background – Radon
Natural Background - Cosmic
Natural Background – Terrestrial
Natural Background – Dose Map
Natural Background – Internal
Natural Background – Medical
Natural Background - Consumer
Natural Background - Other
Natural Background – Total
Risk versus Dose models
Radiation Risk in Perspective
Health Physics Society Position Statement (March 1996):
• Radiogenic health effects (primarily cancer) are observed in humans only at high doses.
• Below this dose, estimation of adverse health effects is speculative since risk of health effects are either too small to be observed or are non-existent.
• Epidemiological studies have not demonstrated adverse health effects in individuals exposed to small doses (less than 10 rem) delivered in a period of many years
Regulatory Limits
Maximum Permissible Dose Limits
Whole Body 5 Rem / yearLens of eye 15 Rem / yearSkin
50 Rem / year
Minor (under 18 y/o) 0.5 Rem / year
Unborn Child of Worker 0.5 Rem over entire
gestation period of DPW
Members of the General Public 0.1 Rem / year
Dose Limit Comparison
• 100,000 rad -Molecular destruction
• 1,000 rad – 100% of people die: CNS syndrome
• 450 rad – LD50 (50% of people die)
• 50 rem/yr – extremity regulatory limit
• 15 rem/yr – lens of the eye regulatory limit
• 10 rem/yr – “whole body” exposure causes measurable blood changes when acute
• 5 rem/yr – whole body regulatory limit for trained radiation workers
• 4.167 rem/qtr – HSC extremity administrative dose limit
• 1.25 rem/qtr – HSC lens of the eye administrative dose limit
• 0.417 rem/qtr – HSC whole body administrative dose limit
RADIATION DETECTION
Detecting Radiation
• Not detectable by any of our natural five sense
• Requires specialized equipment
• Varying types of equipment for different types of radiation and the type of measurements desired
• Knowledge of the technology is key to making sure that you know which detector to choose to which situation
Gas Filled Detectors
Geiger-Mueller
• Geiger-Mueller detectors can be used to survey for a variety of different radioisotopes. Pancake probe GM detectors (shown on the bottom right) are the most efficient type of GM detectors and should be used when available.
Gas Ionization Curves
Scintillators
Photomultiplier tube Sodium Iodide Probe
PROCEDURES
Safety Procedures
1. External Exposure Protection Methods2. Laboratory Procedures3. Emergency Response
Radiation Safety
• External exposure sources– Mitigated by:
• Time• Distance• Shielding• Housekeeping (efficient processes/procedure design)
Dosimetry
• Primary dosimeter is either a OSL or TLD badge
• Sensitive to gamma and hard beta radiations
• Provides RSO with dose information on a quarterly basis
• Does not provide information during a real time exposure to radiation
Dosimetry - Badge
• Dosimeter badges should be worn on either the lapel or waist– Whichever is closest to
the source of radiation
Dosimetry - Ring
• Your ring badge will come with your name on it. Wear the badge with the name plate facing the source of radiation
• Be sure to wear the ring badge under your gloves to capture actual dose to your skin
Safe Practices and Procedures
• Consult HSC eduSafe or Emergency Flipchart and Manuals
• If injuries occur, they take first priority– Call 911– Provide first aid– Monitor individual for
contamination
Detector Use – Device Overview
Detector Use – First Steps
1. Turn meter on
2. Battery check
Detector Use – Device Use Tips
3. Audio on
4. Fast/Slow response
5. Sensitivity setting
Incident Reporting
• Report the following to EHS– Actual OR suspected overexposure incidents– Leakage test failure (shielding is inadequate)– Exposure to the general public– Loss of device
Special Rules (Pregnancy)
– A woman is only pregnant when she submits the paperwork.
– Tighter dose restrictions are applied to protect the baby (no more than 0.5 rem over the course of the pregnancy – 10CFR20)
– A woman has the right to declare and undeclare at any time.
Declared Pregnancy
Security
– Do not be afraid to challenge ANYONE you do not recognize in your lab or lab area.
• Unauthorized personnel should not be in your lab. Asking for identification is appropriate in all circumstances.
– No one other than authorized users should have access to radiation producing devices.
Summary
• What is radiation?– Types of radiation– Biological effects of radiation– Background radiation– Radiation detection
• HSC Procedures– Safety (PPE, storage, etc)– Survey Procedure
Contact Information
• Radiation Safety Officer– Erich Fruchtnicht– [email protected]– 979-436-0551
• Bryan EHS Officer– Marc Goldsmith– [email protected]– 979-436-0559
• Temple EHS Officer– Cristina Bazan– [email protected]– 254-742-7024
• Houston EHS Officer– Stephanie Colman– [email protected]– 713-677-7953
• Dallas EHS Officer– Hiram Patterson– [email protected]– 214-828-8301
• Kingsville EHS Officer– Call the RSO for radiation
questions
Test
• Go to: http://www.tamhsc.edu/ehs/radiation-safety.html• Click on “X-ray Safety Test”• Take test• Click submit