Radiation Safety: Biological effects of radiation Flashcards
ARRT uses
SI units of measurement also known as international
All radiation measurements in radiology fall into two categories
- Radiation in Air
- Radiation in Tissue
Radiation in Air
- exposure
- Air kerma
Radiation in Tissue
-absorbed dose
-equivalent dose
-effective dose
what is exposure
direct measurements of the ionization of air molecules.
-NUMBER of ionizations in air
-measured in the ion chamber
-calculated in Coulumb/kg
what is air kerma
- Measures the energy of ionization in air
-unit of measurement is gray (Gy)
what is the difference of Exposure and Air kerma?
Exposure: Number of Ions
Air kerma: energy or ions
what does KERMA mean
Kinetic energy released in matter
Absorbed dose (D)
Energy absorbed in matter per unit mass
SI units: gray or miligray (Gy)
equivalent dose (EqD)
equivalent dose is a calculated dose
-it is determined by multiplying the absorbed does by the radiation weighting factor that accounts for the higher biological effectiveness(aka ability to cause damage) of certain types of radiation.
alpha particles weighting factors
20
X-rays, Beta particles and Gamma rays weighting factor is what?
1
Fast neurons and protons weighting factor is?
10
what is effective dose?
a calculated dose that takes into account the type of radiation the patient was exposed to (equivalent dose) as well as what part of the body was irradiated.
-expressed in Sieverts (Sv)
what is the tissue weighting factor
accounts for the fact that some tissues are more radiosensitive (at greater risk of cancer than others).
organs that are the most radiosensitive
-Lungs
-colon
-stomach
organs that are the least radiosensitive
brain
bone
skin
agencies involved in radiation protection recommendations
- International Commission on Radiological Protection
- National Council on Radiation protection and measurements (NCRP)
what does the NCRP do?
Publishes scientific research recommendations on radiation protection and measurements in the U.S
what does the ICRP do?
-conducts research and provides recommendations on radiation protection world wide
NCRP #160 chart
chart addresses radiation exposure from all sources to people living in the US
- radon is the largest dose for natural sources
- medicaid imaging: CT is the largest dose
The law of Bergonie and Tribondeau
States the radio sensitivity of a cell is directly proportional to reproductive rate and is inversely proportional to its degree of differentiation
Radio sensitivity increases with:
-Increased rate of cell division
-low degree of specialization (stem cells are very radiosensitive)
- Higher metabolic rate
-Increased oxygenation
-Increased length of time they are actively proliferating. Cell proliferation is the process by which a cell grows and divided to produce 2 daughter cells
Young cells and cells that divide often are going to be _________ sensitive
MORE
Cell cycle stage
G1: first growth phase
S: least radiosensitive, because the cell contains two copies of its DNA
G2: second growth phase
M: mitosis phase. The cell is the most radiosensitive phase because the cell is well oxygenated
Most sensitive cells to least sensitive
MOST
-blood cells ( lymphocytes are the MOST radiosensitive blood cell)
-reproductive cells
-GI= small intestine most radiosensitive
-Epithelial tissue
-Muscle= relatively insensitive because of high specialization and lack of cell division
Nerve= low sensitivity and last
oxygen effect & sensitivity
-Tissue is more sensitive to radiation when it is in an oxygenated state
-oxygen creates free radicals which increase damage to the cell
As OER increases, cell survival _______
decreases
DNA
deoxyribonucleic acid
molecule that carrie’s genetic information for the development and functioning of an organism
-Adenine & thymine
-Guanine & Cytosine
direct vs. Indirect effects to DNA
direct- occurs when radiation transfers its energy directly to the DNA
indirect- more common, radiolysis= interaction with water molecule. (when the x-ray photon hits a water molecule first)
why does indirect happen more often?
Our bodies are made out of 80% of water!
cell cycle in order (PMAT)
- pro phase
- metaphase
- anaphase
- telophase
apoptosis means?
interphase death
dies before the cell divides
Motorized death
dies after one or more mitotic cycles
germs cells divide by________
somatic cells divide by ________
Meiosis
Mitosis
LET: linear energy transfer
LET is the rate at which radiation energy is deposited in matter.
-A higher LET causes more biological harm.
As LET increases, it is ____ penetrating
Also, as LET increases, cell survival rate ________
Higher the LET, the _________ the biological damage
less
decreases
higher
x-ray is ______ LET
low
Relative biological effectiveness
ability of radiation to cause biological damage
RBE is affected by
1. type of radiation
2. dose rate
3. tissue type
as LET goes up, RBE……
goes up!
Lethal dose- LD 50
amount of whole body radiation dose necessary to kill 50% of exposed population in a certain amount of days.
Ex.)
LD 50/30= 50% killed in 30 days
LD 50/60= 50% killed in 60 days
dose response curves
A graphical method describing the relationship between the amount of radiation received and the observed biological effects.
dose response curves will present visually as:
- threshold, or non-threshold
-non threshold starts at zero
-threshold requires a starting number - Liner or nonlinear
-linear = straight line
-non linear = has a curve!
Types of curves
1.) linear non-threshold
2.) linear threshold
3.) Non-linear non-threshold
4.) Non-linear threshold
What does threshold mean?
threshold means there is a certain amount of those required to initiate the response.
-Example skin erythema only occurs after a skin dose of approximately 2 Gy
Non threshold means what?
there is No Dose that is considered safe for that effect .
example any radiation dose is considered to increase the chances of getting leukemia and probability, increased uniformly as dose goes up 
equivalent dose formula
EqD= D x WR
Effective dose formula
EfD= D x WR x WT
Efd is a ______ body dose
whole body dose
collective effective dose 
-used to describe radiation exposure of a population or group from low doses of different sources of ionizing radiation.
Efd x total # of exposed individuals
- Expressed in units of sieverts
entrance skin exposure (ESE)
ESE = (mR x mAS)
the quaintly of radiation entering the patient
DAP meter
A fixated to call a meter housing to measure the quantity of radiation, absorbed by air in the radiation field.
-measures as energy in air
dose area product DAP
used to quantify the risk from radiography & fluoroscopy
DAP= absorbed dose x irradiated area
- unit of dap is in Gy cm^2
Stochastic effects
-effects do NOT have a threshold or irradiation and are considered random.
- NO DOSE IS SAFE
Stochastic effects can be divided into _____ and ______ effects
somatic & genetic
deterministic effects
-is often referred to as tissue reactions
- tissue reactions have a THRESHOLD of irradiation
tissue reactions include skin reactions
- epilation, erythema, desquamation, cataracts, circulatory diseases and other conditions
diagnostic x-ray is a _______ effect 
stochastic 
stochastic effects of radiation on humans 
also known as probabilistic
leukemia, cancer, bone cancer, lung cancer, thyroid cancer, in breast, cancer, local tissue damage, genetic damage 
deterministic effects of radiation on humans (tissue reactions)
acute radiation syndrome skin erythema, cataracts, epilation 
stochastic hints to remember 
if something is random, it is probably going to happen, and there is no known number ( non threshold) 
deterministic hints 
if something is not random, it has been determined, and there is a known number(threshold)
what are somatic effects
-any change in the cell or organ that can be observed and are limited to the exposed population
-harm to person exposed to the radiation
-examples: leukemia
what are genetic effects
-changes in the DNA that is passed on to the next generation
-harm to person i. future generation due to ancestors exposure
ex: congenital abnormality
short term effects
Effects seen within hours, days or weeks of exposure
-epilation, erythema, and nausea
long term effects
effects seen months, years or decades after exposure
-cancers
-leukemia
-cataracts
-genetic effects
acute exposure
-large dose delivered over a short period of time
-more harmful( chernobyl)
chronic exposure
-radiation delivered in small increments over a long period of time
-think about a pt who is in chronic pain
Organ and tissue response to the eye
-Cataractogensis: nonlinear, threshold
organ and tissue response to skin
-erythema
-desquamation
-epilation or alopecia
* they all happen at a threshold which is a certain point
Gonadal response to females
-temporary sterility 2 Gy to the ovaries
-permanent sterility 5 Gy
gondal response to males
-Depressed sperm count as low as 0.1 Gy
-Permanent sterility 5-6 Gy
-0.1 Gy can result in genetic mutations
lethal effects
are induced by radiation before or immediately after implantation of the embryo into the uterine wall
Three stages of pregnancy
Pre-Implantation- 0-10 days
Organogenesis- 10 days- 6 weeks
Fetal Period- 6 weeks- birth
Preimplantation is the ______ sensitive stage to the lethal effects of radiation
Most
Required conditions for Acute Radiation syndromes
- The radiation dose must be late, greater than 0.7 grays
-The dose usually must be external - The radiation must be penetrating
- The entire body
-The dose must have been delivered in a short time
-
Hematopoietic syndrome ( bone marrow )
- due to depression of the blood forming organs
- death within 3-6 weeks
- occurs 1-10 Gy
Gastrointestinal death
-small bowel is primarily
-affected death within one week
-occurs between 10 to 50 Gy
Central nervous system
-principal organ affected is the brain -death within hours or days
-whole body doses, 50 GY
Acute radiation syndrome phases
1.) Prodromal stage
2.) Latent stage
3.) Manifest illness stage
4.) Recovery or death stage
Prodromal stage
The classic symptoms for this stage are nausea, vomiting, as well as anorexia, and possibly diarrhea which occur from minutes to days following exposure. The symptoms may last for minutes up to several days. 
latent stage
in this stage, the patient looks and feels generally healthy for a few hours, or even up to a few weeks 
Manifest illness stage
and this stage, the symptoms depend on the specific syndrome, such as (GI, CNS) 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 last from several weeks up to two years.
