Ch. 11 Radiobiology & Radiation Safety Flashcards
biologic damage produced from received exposure based on radiation type
- Pts receive both an exposure & absorbed dose (absorbed dose will always be greater than exposure)
-absorbed dose & dose equivalent are always identical numbers
Radiation Weighing Factor
-Ionization may occur to any part of the cell including the material that makes up the membrane, the water within the membrane, or the DNA forming free radicals
-some damage may cause malfunction to the cell
Biological effects of radiation: cellular level
the amount of xray energy transferred on average per the length of passage through the tissue (explains how much radiation was absorbed in a given section)
- high transfers of a large amount into a small section can do more damage)
Linear Energy Transfer (LET)
when tissues contain more oxygen, they are more sensitive
Oxygen Enhancement Ratio (OER)
Age (younger is more sensitive)
Differentiation (Simple cells are more sensitive)
Metabolic rate (cells that use energy more rapidly are more sensitive)
mitotic rate (cells that multiply fast are more sensitive)
Cell sensitivity based on the Law of Bergonie & Tribondeau
Blood cells, Thyroid gland, breast tissue, cells with mucous
cell types that are extremely sensitive
nerve, muscle, bone cells
cell types that are not sensitive
tissues of embryos, fetuses, infants, children, adolescents
tissue types that are very sensitive
when do destructive interaction occur?
at atomic level
effects observed within 3 months of exposure
- very predictable
- quantity of exposure is required to produce the effects
short-term effects
hematologic system (blood)
gastrointestinal system (digestive tract)
central nervous system (brain & spinal cord)
- compromised immune system caused by death of white blood cells
- unable to fight off infections
- fatal, but suffering is prolonged
acute radiation syndrome (ARS)
“latent effects” observed several years after exposure & may not be apparent until 30 years
- 10-15 years is when the greatest % of effects are observed
- very random & unpredictable
Long-term effects
cataracts
increased risk of carcinogenesis (cancer)
shortened life span
leukemia (blood/bone marrow cancer)
typical long-term effects
effects the body & tissues of the irradiated individual
Somatic
occur as a result of damage to the reproductive cells of an irradiated person
-defects are seen in children/grandchildren
-mutations/changes to reproductive cells after gonads have been exposed
Genetic
“as low as reasonable achievable”
- reduce radiation by avoiding repeat exposures, use small radiation fields, use the highest kvp. maintain 40” SID, Shield whenever possible
ALARA
fluoroscpy & mobile radiopgraphy
greatest occupational risk
Time, Distance, Shielding
3 principle methods of personnel protection
dosimeters use aluminum oxide as a radiation detector & is processed using laser light
-measures small doses more accurately with long term stability
Optically Stimulated Luminescence (OSL) Dosimeter
worn at collar level outside of lead apron
- a second dosimeter worn at waist level under lead apron if pregenat
where are dosimeters worn?
a system used to calculate the upper limit of occupational exposure
-applies to individuals over 18 & are non pregnant
-assumed to be whole-body dose
Effective Dose Limit
lifetime effective dose in mSv should not exceed 10x the person’s age
(Ex: 30 y/o = 300 mSv)
Cumulative Effective Dose (CumEfD)
monthly limit to the embryo/fetus for a pregnant worker
0.5mSv
annual effective dose limit
50 mSv
effective dose limit for lens of the eye
150 mSv
what is the dose equivalent biologic effect of each of the following:
- blood
-Radiation Sickness (nausea, diarrhea)
-Radiation burn (erythema “skin redness)
-genetic effects (temporary sterility of gonads)
-50% chance of death (LD50/30)
-death
-250 mSv
-1500 mSv
-2000 mSv
-2500 mSv
-3000mSv
-6000 mSv
What is the SI unit and the Standard unit for Air KERMA (Exposre)
SI unit:
-Gray or Coulomb/kilogram
Standard Unit:
-Roentgen
what is the SI unit and the Standard unit for Absorbed Dose
SI unit:
- Gray
Standard Unit:
-Rad
What is the SI unit and Standard unit for Occupational Dose (Dose Equivalent)
SI unit:
- Sievert
Standard unit:
-Rem
what is the SI unit and the Standard unit for Radioactivity
SI Unit
- Becquerel
Standard unit:
-Curie
