Week 14 - Radiation Safety Flashcards
What is PPE for radiation?
Lead aprons
Thyroid shields
Eye protection
Movable shields for all personnel in the room
What are the types of electromagnetic radiation?
Radio
Microwaves
Infrared
Visible Light
Ultraviolet
X-Rays (used to view inside of bodies and objects)
Gamma Rays (used in medicine for killing cancer cells)
*x-rays and gamma rays are the same thing, the only difference is how they are produced – they have short wavelength and high energy, thus very penetrating to human tissue
X-rays can travel forever until an object is encountered, then what three interactions can occur?
Absorption - patient absorbs the x-rays
Transmission - x-rays pass through pt and there is no interaction
Scattering - produced when original x-rays from machine interact with the outermost electrons from the target (pt and table), incoming photon changes direction and looses energy (lower energy makes it easier to absorb) – results in occupational exposure
What is responsible for most occupational radiation exposure received during diagnostic x-ray procedures?
x-ray scattering
What is the most common molecule in the body to undergo ionization?
Water molecules – major concern with occupational radiation exposure
-ionized water molecules are free radicals that are more reactive chemically than neutral atoms and can form compounds that may cause chemical change in tissue by interfering with cell division and metabolism
What is indirectly ionizing radiation? What is its effect?
X-ray Photons
- photons transfer energy to a molecule which then excites or ionizes that molecule
- free radicals produced by the radiolysis (ionization) of water
Effect = propagation of ion
- this again breaks molecular bonds and forms free radicals
- radicals formed by a direct radiation effect travel/diffuse far enough to reach target of interest (DNA) in order to ionize target
- propagation reactions are a very common examples of indirect radiation damage
What is Alpha Radiation?
A form of particulate radiation – NOT electromagnetic radiation
- a Helium nucleus with no electrons
- extremely heavy and very strongly charged (2+)
- very damaging (high LET)
- travels only a short distance in tissue
- easy to shield, not significant source of x-ray exposure
- used as Radium 223 (Xofigo) Therapy for bone mets in prostate cancer
- Radon 222 Gas = environmental exposure
What is Beta Radiation?
A form of particulate radiation – NOT electromagnetic radiation
- basically a “free electron”
- small mass but charged (-1)
- relatively high LET
- doesn’t travel very far before being “captured” by a molecule
- commonly used for targeted Radioablation Therapies
Define RAD and REM
RAD: Radiation Absorbed Dose
-measure of radiation levels in the OR from radiation sources
REM: Radiation Equivalent Man
-measure of the type of human tissue exposed by specific forms of radiation
What is the Law of Bergonie & Tribondeau?
The principle stating that the radiosensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation
- stem cells are radiosensitive – mature cells are radioresistant (blood & bone marrow, reproductive tissue)
- younger tissues and organs are radiosensitive (pediatrics)
- tissues with high metabolic activity are radiosensitive (thyroid gland)
- high proliferation rate for cells and a high growth rate for tissues result in increased radiosensitivity (skin, lining of GI tract)
Define Linear Energy Transfer (LET)
a measure of the rate at which energy is transferred from ionizing radiation to soft tissue
- the ability of ionizing radiation to produce a biologic response increases as the LET of the radiation increases
- when LET is high, ionizations occur frequently, so the probability of interaction with the target molecule is higher
What are the risks of harm from radiation exposure?
- Type of radiation
- Size of dose
- Rate at which dose is delivered
- Part of body exposed (tissue volume exposed, stage of cell division, differentiation of the cell)
- Age of the individual exposed
- Health of the individual exposed
What are threshold effects?
Certain biological effects are caused when a radiation dose greater than some threshold value is received
*this does not occur at occupational dose levels (exception of potential cataract formation following chronic, high exposure to the lens of the eye)
- Cataracts = 200 REM (acute)
- Cataracts = 800 REM (chronic)
- Severe skin injury = 1,500 REM
- Teratogenic effects = 20 REM
What are the average patient radiation dose rates with fluoroscopy?
Conventional Fluoroscopy = 1-10 rad/min
High dose rate fluoroscopy = 6-10 rad/min
*higher the patient dose, the higher the amount of scatter
What is the Linear No-Threshold Hypothesis (LNTH) in radiation?
Non-threshold effects are radiation induced effects that occur with an incidence presumed to be directly related to the dose level – cataracts, epilation, cancer
- If radiation dose is doubled, the potential response to the radiation is likewise doubled
- Radiation induced cancer and genetic effects follow this linear dose-response relationship
