Ch 33 Deterministic Effects Flashcards
There have been no reported cases of death after exposures to…
Diagnostic Radiation
Early pioneers died from _________ effects of x-ray exposure
Stochastic
What was Chernobyl?
- Nuclear reactor accident in 1986
- 30 people experienced ARS and died
What was the 3 mile island?
-Partial core meltdown in 1979
-No one died or was seriously
injured
Is employment in the nuclear power industry safe?
Yes
When do symptoms from the Prodromal period begin?
Within hours of exposure and
continue for up to 1-2 days
What are early symptoms of the Prodromal period?
- Nausea
- Vomiting
- Diarrhea
- Leukopenia (decreased white blood cell count)
What is the manifest illness?
Onset of symptoms after the latent period
What are the (3) types of Manifest illness’?
- Hematologic
- Gastrointestinal
- Central Nervous System
What dose of radiation produces the GI Syndrome?
1,000-5,000 rad (10-50gy)
When do prodromal symptoms for the GI Syndrome occur?
Within hours of exposure
How long is the latent period for the GI Syndrome?
3-5 days
What are symptoms of the manifest period for the GI Syndrome?
- Nausea, vomiting, diarrhea, loss of appetite, lethargy
- Diarrhea persists and becomes more severe leading to watery and bloody stools
When does death occur for the GI syndrome?
4-10 days
Due to severe damage to intestinal cells (dehydration of cells)
What happens to the electrolyte balance during GI syndrome?
It is destroyed
What are the most sensitive cells in the body?
Stem cells
What does LD stand for?
Lethal Dose
What does LD 50/60 mean?
Lethal dose of 50% of the people in 60 days
Acute radiation lethality follows a…
Nonlinear threshold dose response relationship
With medical support, how much radiation can humans tolerate?
350-850
What is considered a lethal dose of radiation?
350 rad (3.5gy)
How is Acute Radiation lethality measured?
LD 50/60 350
What can cell death cause?
Impaired organ or tissue function
What organs/ tissue, can be effected by partial body radiation?
Every organ and tissue
What determines the level of tissue response?
Depends on intrinsic radiosensitivity and the kinetics of cell proliferation and maturation
What are the local tissues that are immediately affected by radiation exposure?
Skin, gonads, and bone marrow
All early radiation responses follow a…
Threshold type dose response type relationship
What is a Threshold type dose response relationship
- A minimum dose is needed to produce a response
- Once the minimum dose is exceeded the severity of response increases with increasing dose
Define
Erythema-
Sunburn like redding of the skin
What is the 1st observed biologic response to radiation?
Erythema
Define
Desquamation-
- Ulceration and denudation of the skin
- Shedding of outer layer of skin
How long will it take for someone to show erythema?
10-30 mins of radiation exposure
Define
Epilation-
Loss of hair
Responses to doses as low as _____ have been observed in the gonads.
10 rad (100mGy)
Human gonads are very sensitive to radiation. T/F
True
What are the male gonads
Cells of the Testes
Why do gonads respond differently to radiation when compared to other cells?
Because of the progression from the stem cell to the mature cell
What are the female gonads?
Cells of the Ovaries
What is the most radiosensitive (vulnerable) phase in male cell maturation?
Spermatogenia
What is the most radiosensitive (vulnerable) phase in female cell maturation?
Mature Follicle
What is the stem cell in males?
Spermatogonia
What is the stem cell in females?
Oogonia
How many ova are available for fertilization over lifetime?
400-500
What is a female’s mature germ cell called?
Ovum (egg)
When are female mature germ cells (ovum) produced?
At puberty
How often are male germ cells produced?
Continuously
What is a males mature germ cell called?
Spermatozoa (sperm)
How long does it take for the male germ cell to mature?
3-5 weeks
When do female stem cells develop?
During fetal life
Irradiation to the ovaries early in life reduces their ______ through germ cell death
Size (atrophy)
When is radio sensitivity it’s highest?
During fetal life and early childhood
When is radio sensitivity it’s lowest?
20-30 y/o
When does radio sensitivity pick back up?
After age 30
Effects of dose on the ovaries: 10 rad (100 mGyt)
Delay or suppression of menstruation
Effects of dose on ovaries: 200 rad (2 Gyt)
Temporary infertility
Effects of dose on ovaries: 500 rad (5 Gyt)
Permanent sterility
Effects of dose on ovaries:
200-500 rad (2-5 Gyt)
Genetic mutations
When does atrophy occur to the testes?
After high doses of radiation
The spermatogonial stem cells are the most ____________.
Radiosensitive
When is sperm cell count affected by radiation?
Several weeks after exposure
Other than spermatogonial stem cells, how does radiation effect other cells in the development phase?
They are mostly radioresistant
Effects of dose on testes: 10 rad (100 mGy t)
Reduction in number of sperm
Effects of dose on testes: 200 rad (2 Gyt)
Temporary infertility (starts 2 months after irratiation and lasts up to 12 mths)
Effects of dose on testes: 500 rad (5 Gyt)
Permanent sterility
What does the hemopoietic system consist of?
- Bone marrow
- Circulating blood
- Lymphoid tissue
Where are most blood cells manufactured?
In the bone marrow
Where do cells of the hemopoietic system develop from?
A pluripotential stem cell
What are the first cells to be affected by radiation exposure?
Lymphocytes
___________ experiences a rapid rise, then rapidly decrease
Granulocytes
How long does recovery of granulocytes take?
Approximately 2 months
When do Lymphocytes begin to reduce in number after radiation exposure?
Within minutes or hours of exposure, slow to recover
What are the least sensitive of blood cells?
Erythrocytes
How long does it take for Erythrocytes to recover?
6-12 mths
Do Thrombocytes deplete slowly or quickly?
Slowly, recovery takes about 2 months
What is Cytogenetics?
The study of the genetics of cells, particularly the cell chromosomes
How many types of chromosome aberrations can be radiation induced?
Nearly all of them
Human peripheral ___________ are used for cytogenetic analysis.
Lymphocytes
When does chromosome damage occur?
- At the time of radiation
- May not be measured for months or years after irradiation
Cytogenetic Effects of Radiation follows a…
Non threshold dose response relationship
What is a Karotype?
Chromosome map
Each cell consists of:
- 22 paris of autosomes
- 1 pair of sex chromosomes
What does a DNA hit produce?
Disruption of the molecular structure
What does a chromosome hit produce?
Visible derangement of the chromosome
What is more severe, a chromosome hit or a DNA hit?
Chromosome (chromosomes contain DNA)
Single hit chromosome aberrations are produced with a…
Linear, non threshold dose response relationship
Multi hit chromosome aberrations are produced with a…
Non linear, non threshold dose response relationship
Are diagnostic x-ray beams intense enough or large enough to cause death?
No
What type of exposure does Hematologic, GI, and CNS Syndrome all require?
Whole body exposure
What is ARS (Acute Radiation Syndrome?)
Sequence of events that follow high level radiation exposure leading to death within days or weeks
What are the (3) stages of ARS (Acute Radiation Syndrome?)
- Prodromal Period
- Latent Period
- Manifest Illness
What is the Latent Period?
- Time after the exposure
- No signs/ symptoms of radiation sickness
How long does the Latent Period last?
- Hours to weeks
- The higher the dose, the shorter the latent period
What period may mislead one to think recovery has occurred?
Latent period
What is produced by radiation doses of 200-1,000 rad
Hematologic Syndrome
What is characterized by a reduction in white blood cells, red blood cells, and platelets?
Hematologic Syndrome
What is produced by radiation doses greater than 5,000 rad?
Central Nervous System (CNS Syndrome)
During the CNS syndrome, when do the prodromal symptoms occur?
Within minutes
During the prodromal period, what dose will begin producing violent symptoms?
1,000 rad (Gy t)
At higher doses it is difficult to separate the ___________ syndrome from the __________ illness.
Prodromal/ Manifest
At low doses, there may be no ________ period.
Prodromal
At high doses, the latent period may ________.
Disappear
What is the name for the immediate response of radiation sickness?
Prodromal Period
How severe are the prodromal symptoms during the Hematologic Syndrome?
Mild
What does the manifest illness consist of during a non lethal dose of Hematologic Syndrome?
- Vomiting
- Mild Diarrhea
- Malaise
- Lethargy
- Fever
If dose is not lethal during the Hematologic Syndrome, when does recovery begin?
2-4 weeks, can last up to 6 months
During the Hematologic Syndrome, what happens if the dose is lethal?
- Reduction in blood cells (defense against infection)
- Hemorrhage and dehydration
- Death due to infection, electrolyte imbalance, and dehydration
When do prodromal symptoms occur during the CNS Syndrome?
Within minutes of exposure
How long does the latent period last during the CNS syndrome
Up to 12 hours
During the CNS Syndrome what are the Manifest illnesses?
- Disorientation
- Loss of muscle coordination,
- Difficulty breathing,
- Seizures
- Loss of equilibrium
- Ataxia
- Lethargy
What does ataxia mean?
Inability to coordinate muscles
During the CNS syndrome, what is the end result of the manifest illness?
- Death within days
- Pt lapses into coma and dies
- Ultimate cause of death is elevated fluid in the brain.
What is the mean survival time?
As whole body radiation dose increases, the average time between exposure and death decreases
When radiation dose increases from 200-1,000 rad, mean survival time decreases from _____ to ____ days
60/ 4
What is the mean survival time of Hematologic Syndrome?
Varies with dose (60-4 days)
What is the mean survival time of GI Syndrome?
Relatively consistent at 4 days
What is he mean survival time of the CNS syndrome?
Varies with dose (3 days to hours)
What cell layers of the skin participate in the response to radiation exposure?
All of them
At what rate are skin cells replaced?
2% per day
What are the most vulnerable skin cells?
Basal cells
Describe Basal cells:
- Most vulnerable to radiation
- Lowest layer of the outer skin layer
- Stem cells that mature into the cells of the epidermis
- Most radiosensitive
Skin effects follow a…
Non linear, threshold dose response relationship
What does SED mean?
Skin Erythema Dose
What is SED (Skin Erythema Dose?)
- Dose of radiation that causes erythema
- SED 50 is about 500 rad (Gy 1)
* Dose required to affect 50% irradiated
