Early Effects of Radiation Flashcards
Total Body exposure
when the total body is exposed, so are critical organs
- health effects in this case, will depend on the radiation dose received by the critical organs
- all body systems affected
acute exposure
short-term, high-level exposure
chronic exposure
long-term, low-level exposure
somatic effects
biological damage from ionizing radiation to body cells
non-stochastic
the severity of the effect varies with the dose and for which a threshold value exists
- aka deterministic
Stochastic
- increased levels of exposure make these health effects more likely to occur (probability) but does not influence the type or severity of the effect
Early deterministic effects
- substantial dose is required
- severity is dose related (not typically diagnostic doses)
- have a threshold
- they appear within minutes to weeks
what leads to Acute Radiation Syndrome (ARS)?
- when whole body is exposed to a large dose over short time of ionizing radiation
where is the information of early deterministic effects gathered
- Hiroshima: atomic bomb survivors
- Marshall Islanders: atomic bomb testing fallout
- Chernobyl: nuclear radiation power plant accident victims
- Radiation therapy patients
Whole Body exposures
- very large exposures
What is acute radiation syndrome (ARS)?
the sequence of events that follows high-level radiation exposure leading to deaths within days or weeks
- must reach a threshold - deterministic
- diagnostic exposures do not lead to this
- exposure to nuclear weapons and nuclear energy fields
what are the stages of ARS?
- prodromal period
- latent period
- manifest period
- recovery or death
prodromal stage
- at doses above approx. 1 Gy (100 rad) delivered to total body
- Signs and symptoms of radiation sickness may appear
- NVD (nausea, vomiting, diarrhea)
- Hours to a few days
radiation sickness
- increased with dose received
- occur within hours of the radiation
NVD
- reduction in the white blood count (leukopenia)
Latent Stage
- the patient looks and feels generally healthy for a few hours or even up to a few weeks - subject is free of visible effects
- either recovery or lethal effects begins
how long is the latent phase?
- hours of less (50 Gy)
- weeks (1-5 Gy)
Manifest Illness
- specific sings/symptoms of a particular syndrome
- symptoms depend on the specific syndrome and last from hours up to months
what three syndromes related to dose may occur?
- Hematologic Syndrome (bone marrow syndrome)
- Gastrointestinal Syndrome (GI)
- Central Nervous System Syndrome (CNS) (Cardiovascular Syndrome (CV))
Hematologic Syndrome
Dose: 1-10 Gy
Survival time: 6-8 weeks (doses over 2 Gy)
Gastrointestinal Syndrome
Dose: 6 to 50 Gy
Survival time: 3 to 10 days
Central Nervous System Syndrome
Dose: above 50 Gy
Survival time: several hours to 2-3 days
Hematopoietic Syndrome
Dose: Whole body 1-10 Gy - damage to bone marrow
- blood production, most radiosensitive vital organ system in humans
- Prodromal stage (NVD): mild, begins in a few hours to several days.
- Latent period: about 4 weeks, blood cells declining in number
- Manifest Illness Stage – NVD, anorexia, malaise, lethargy & fever
*survival possible range of 1-2 Gy
- Primary cause of death is the destruction of the bone marrow, resulting in infection and hemorrhage.
- Depletion of blood cells (red, white, platelets) -> death by infection
- mean survival of 6-8 wks.
Gastrointestinal Syndrome
- Whole body dose of 6 - 50 Gy (6 Gy threshold)
- damage to GI and bone marrow: lining of GI tract → dehydration
- severe infection, fluid loss or electrolyte imbalance
- Prodromal stage (NVD): within hours, lasts ≤ 1 day, severe NVD
- Latent period: 2nd - 5th day
- Manifest illness: 5th - 10th day
lethargy, loss of appetite, malaise, anorexia, severe diarrhea, fever, dehydration, and electrolyte imbalance. - Destructive and irreparable changes in the GI tract and bone marrow usually cause infection, dehydration, and electrolyte imbalance. Death usually occurs within 2 weeks.
- death within 3~14 days
Central Nervous System Syndrome (Cerbrovascular)
- > 50 Gy
- death in few hours to 3 days after 50 Gy
- blood vessel damage → intracranial pressure
- death before symptoms of two previous can occur
- Prodromal stage (severe NVD): lasts a few hours extreme nervousness, confusion, burning sensations, loss of consciousness
- Latent period: a few hours
- Manifest Illness Stage: 5-6 hours after exposure - convulsions, coma - Death within 3 days - due to collapse of the circulatory system as well as increased pressure in the cranial vault as the result of increased fluid content caused by edema, vasculitis, and meningitis.
Lethal Dose
- For adult humans the estimated dose is 3.0 to 4.0 Gy without medical support
- Lethal dose 100 is 6 Gy without medical support.
- Humans with support have tolerated doses as high as 8.5 Gy.
LD 50/30
Signifies the whole body dose of radiation that can be lethal to 50% of the exposed population within 30 days
- Quantitative measurement that is fairly precise when appplied to experimental animals
Local Tissue Damage - partial body exposure
- a destructive response in biological tissue can occur when any part of the human body receives high radiation dose
- a significant cell death usually results after a substantial partial-body exposure. This leads to atrophy of organs and tissues
consequence of local tissue damage
- Organs and tissues sustaining such damage may lose their ability to function, or they may recover
- Radiodermatitis
local tissue damage recovery
- If recovery occurs, it may be partial or complete, depending on the type of cells involved and the dose of radiation received.
- If organ and tissue recovery fails to occur, necrosis, or death, of the irradiated biologic structure results.
Organ and tissue response to radiation exposure depends on?
- radiosensitivty
- reproductive characteristics
- growth rate
Some local tissues suffer immediate consequences from high radiation doses
- skin
- male and female reproductive organs
- bone marrow
layers of the skin
- Epidermis (outer layer)
- Dermis (middle layer)
- Hypodermis (subcutaneous layer)
accessory structures of the skin
- hair follicles
- sensory receptors
- sebaceous glands
- sweat glands
skin radio sensitivity
ongoing regeneration so increased radio sensitivity
Radiodermatitis
reddening (erythema) of the skin that can eventually lead to cancerous lesions
effects of ionizing radiation on the skin?
- radiodermatitis
- Single Dose of 2 Gy (2000 mSv) -> 24 - 48hrs later - desquamation
- Epilation or loss of hair (alopecia)
- Oncology patients receiving orthovoltage radiation therapy treatment have demonstrated significant evidence of skin damage.
hair loss due to ionizing radiation
- Moderate doses of radiation may result in temporary hair loss. (3 Gy) (3000 mSv)
- Large doses of radiation may result in permanent hair loss. (7 Gy) (7000 mSv)
- Historical evidence of treating skin diseases such as ringworm
What is desquamation?
shedding of outer layer of skin (10Gy) (10000 mSv)
epithelial tissue
body constantly regenerates, therefore highly radiosensitive
muscle tissue
highly specialized, relatively insensitive to radiation
nervous tissue
- Nerve tissue in the human adult: highly specialized
- Nerve tissue in the embryo-fetus: more radiosensitive, especially 8 to 15 weeks after gestation
Reproductive cells
- Spermatogonia: doses as low as 0.1 Gy (100 mSv) can depress sperm count
- Ova: doses as low as 0.1 Gy (100 mSv) may delay or suppress menstruation
- Testes of males and ovaries of females do not respond in the same way to radiation
Development of the male and female germ cells
- Stem cells constantly reproduce
- Happening all the time
- Process 3-5 weeks
sperm cells
- constantly reproduce
- stem cells to mature cells
oogonia
multiply to millions of cells only during fetal development than steadily decline
- produced before birth
- steadily decline throughout life
effects of ionizing radiation on the reproductive system
Radiosensitivity of human germ cells
- Lymphocytes are the most sensitive cells in humans but spermatogonia are the second most sensitive
Gonadal dose of ionizing radiation that will cause temporary sterility
Female and Male: 2 Gy (2000 mSv) may last for 12 months
Fertility will return however there could be chromosomal abnormalities
Gonadal dose of ionizing radiation that will cause permanent sterility
Male or female: 5 Gy (5000 mSv)
what are the primary stochastic effects
cancer, leukaemia and genetic defects
Hematopoietic system consists of?
bone marrow, circulating blood, and lymphoid organs (lymph nodes, spleen, and thymus gland)
cells of hematopoietic system all develop from which single precursor cell?
pluripotential stem cell
what do pluripotential stem cells develop into?
- lymphocytes
- granulocytes
- platelets
- erythrocytes
what does hematologic depression cause?
- depletion of immature blood cells
- repopulation after a period of recovery
hematologic effects
Life span perspective
- Lymphocytes (few hours); - Erythrocytes (up to 120 days)
Whole-body dose of ionizing radiation as low as 0.25 Gy (250 mSv)would produce a measurable hematologic depression.
- Radiosensitivity of lymphocytes is greatest (always rapidly dividing)
- Lymphocytes protect the body by producing antibodies, only live 24 hours
why are radiation therapy patients usually immunocompromised?
0.5 Gy (500 mSv) can result in 0 lymphocytes and recovery takes a couple of months
3 stages of gestation in humans
- preimplantation
- organogenesis
- fetal stage
what makes up the first trimester?
- preimplantation
- organogenesis
- first trimester is most crucial stage
- 3 months - most sensitive
- fetus becomes more resistant with progression through second and third trimesters
preimplantation
- conception to 9 days, fertilized ovum
- highly sensitive cells
- High probability of being fatal -> prenatal death most likely, spontaneous abortion
- 0.05 - 0.15 Gy (50 – 150 mSv) death will occur
organogenesis
- starts implantation, 10th day to 12th week post conception
- undifferentiated cells starting to differentiate into organ systems
- abnormalities are congenital and include: growth inhibition, intellectual disabilities, microcephaly, genital deformities, sensory organ damage
- can result in neonatal death (death at birth)
fetal stage
- from 12th week on
- primarily growth
- nervous tissue
- abnormalities can include cancer and functional disorders during childhood
- may lead to sterility
what is a syndrome?
a collection of symptoms
What is orthovoltage?
100-500 KeV (200-300 avg)
Prior to TLD’s, how was occupational exposure tracked?
- film badges
- blood tests
