5.1 Biologic Effects of Radiation Flashcards
Dose-Response Relationship also referred to as
Dose-Response Curve
is a graphical
relationship between observed effects (response) from radiation
and dose of radiation received
Dose-Response Relationship
these are used to design therapeutic treatment routines for
cancer and provide the basis for radiation management activities
Dose-Response Relationship
means that an observed response is directly proportional
to the dose
Linear
means that an observed response is not directly
proportional to the dose
Nonlinear
assumes that there is a radiation level reached below which
there would be no effects observed
Threshold
point at which biologic response to an increasing stimulation
first occurs
Threshold
assumes that any radiation dose produces an effect
Nonthreshold
are those biologic somatic effects of ionizing radiation that
exhibit a threshold dose below which the effect does not
normally occur and above which the severity of the biologic
damage increases as the dose increases
Deterministic Effects
are nonthreshold, randomly occurring biologic somatic changes
in which the chance of occurrence of the effect rather than the
severity of the effect is proportional to the dose of ionizing
radiation
Stochastic
Deterministic Effects:
Acute Radiation Syndrome
- Hematologic Syndrome
- Gastrointestinal Syndrome
- Central Nervous System Syndrome
Clinical Signs and Symptoms:
Prodromal
Nausea, vomiting, diarrhea
Clinical Signs and Symptoms:
Latent
None
Clinical Signs and Symptoms:
Hematologic
Nausea, vomiting, diarrhea,
anemia, leukopenia, hemorrhage, fever, infection
Clinical Signs and Symptoms:
Gastrointestinal
Same as hematologic plus electrolyte imbalance,
lethargy, fatigue, shock
Clinical Signs and Symptoms:
Central Nervous System
Same as gastrointestinal plus ataxia, edema, system vasculitis, meningitis
Approximate Dose for Prodromal
> 1 Gyt
Approximate Dose for Latent
1-100 Gyt
Approximate Dose for Hematologic
2-10 Gyt
Approximate Dose for Gastrointestinal
10-50 Gyt
Approximate Dose for Central Nervous System
> 50 Gyt
Mean Survival Time (Days) for Prodromal
none
Mean Survival Time (Days) for Latent
none
Mean Survival Time (Days) for Hematologic
10-60
Mean Survival Time (Days) for Gastrointestinal
4-10
Mean Survival Time (Days) for Central Nervous System
0-3
Acute Radiation Syndrome (ARS) :
Response Stages
- Prodromal Period
- Latent Period
- Manifest Illness Stage
- Recovery or Death
At radiation doses >1 Gyt (100 rad), signs and symptoms of
radiation sickness may appear within minutes to hours
Prodromal Period
Symptoms of early radiation sickness are often nausea,
vomiting, diarrhea, and leukopenia
Prodromal Period
This period may last from a few hours to a couple of days
Prodromal Period
The severity of the symptoms is dose related; the higher the
dose, the shorter the period
Prodromal Period
Prodromal Symptoms of 1.2 Gy (120 rads)
Anorexia
Prodromal Symptoms of 1.7 Gy (170 rads)
Nausea
Prodromal Symptoms of 2.1 Gy (210 rads)
Vomiting
Prodromal Symptoms of 2.4 Gy (240 rads)
Diarrhea
A period of well-being
Latent Period
is sometimes
mistakenly thought to indicate an early recovery from a moderate radiation dose
Latent Period
extends from hours or less (at doses in
excess of 50 Gyt) to weeks (at doses from 1 to 5 Gyt)
Latent Period
During this period, the patient is noticeably ill, showing signs
and symptoms of the specific syndrome reflecting the organ
system which is damaged
Manifest Illness Stage
Lasts from minutes to weeks, depending on dose
Manifest Illness Stage
is characterized by a reduction
in white blood cells, red blood cells, and platelets
Hematologic Syndrome
Radiation doses in the range of approximately 2 to 10 Gyt
200–1000 rad
Hematologic Syndrome
Hematologic Syndrome:
Prodromal period
–occurs in a matter of few hours and may persist for several
days post exposure
Hematologic Syndrome:
Latent period
can extend up to 4 weeks
–is characterized by possible vomiting, mild diarrhea, body
malaise, lethargy, and fever. Each type of blood cell then
follows a characteristic pattern of depletion
–If the dose is not lethal, recovery begins in 2-4 weeks, may
require up to 6 mos for full recovery
–If the radiation injury is severe enough, it could lead to
death. Just before death, hemorrhage and dehydration may
be pronounced.
Hematologic Syndrome:
Manifest Illness period
Radiation doses of approximately 10 to 50 Gyt (1000–5000
rad)
Gastrointestinal Syndrome
Gastrointestinal Syndrome: Prodromal period
Symptoms of vomiting and diarrhea occur within hours of
exposure and persist for hours up to a day
Gastrointestinal Syndrome: Latent period
3 to 5 days
begins with a second wave of nausea and vomiting followed by
diarrhea, then gets anorexic and lethargic. The diarrhea persists
and becomes more severe, leading to loose and then watery
and bloody stools. Supportive therapy cannot prevent the rapid
progression of symptoms that ultimately leads to death within 4
to 10 days of exposure.
Gastrointestinal Syndrome: Manifest Illness period
Radiation doses in excess of 50 Gyt (5000 rad)
Central Nervous System
characterized by increased intracranial pressure,
inflammatory changes in the blood vessels of the brain
(vasculitis), and inflammation of the meninges (meningitis)
Central Nervous System
Central Nervous System:
Prodromal period
The patient may become extremely nervous and confused,
may describe a burning sensation in the skin, may lose vision,
and can even lose consciousness within the first hour
Central Nervous System:
Latent period
Lasts up to 12 hours
Symptoms of the prodromal stage return but are more
severe. The person becomes disoriented; loses muscle
coordination; has difficulty breathing; may go into convulsive
seizures; experiences loss of equilibrium, ataxia, and lethargy;
lapses into a coma; and dies
Central Nervous System:
Manifest Illness period
the whole body radiation
dose that causes 50% of
irradiated subjects to die within
60 days
LD 50/60
LD 50/60 (Gyt) of Pig
2.5
LD 50/60 (Gyt) of Dog
2.8
LD 50/60 (Gyt) of Human
3.5
LD 50/60 (Gyt) of Guinea pig
4.3
LD 50/60 (Gyt) of Monkey
4.8
LD 50/60 (Gyt) of Opossum
5.1
LD 50/60 (Gyt) of Mouse
6.2
LD 50/60 (Gyt) of Goldfish
7.0
LD 50/60 (Gyt) of Hamster
7.0
LD 50/60 (Gyt) of Rat
7.1
LD 50/60 (Gyt) of Rabbit
7.3
LD 50/60 (Gyt) of Gerbil
10.5
LD 50/60 (Gyt) of Turtle
15
LD 50/60 (Gyt) of Armadilo
20
LD 50/60 (Gyt) of Newt
30
LD 50/60 (Gyt) of Cockroach
100
As the whole-body radiation
dose increases, the average
time between exposure and
death decreases
Mean Survival Time
All organs and body tissues can be affected by partial body
irradiation and result in cell death
Local Tissue Damage
Tissue response depends on its radiosensitivity, reproduction,
and maturation rates
Local Tissue Damage
Local Tissue Damage common parts
Skin,
Gonads,
Bone Marrow
reduction in size of cell, organ or tissue
Atrophy
Skin consist of 3 layers:
epidermis,
dermis,
hypodermis
Skin cells are replaced at the rate of
approx ___ per day
2%
sunburn-like reddening of
the skin
Erythema
shedding of outer
layer of skin
Desquamation
defined as the received quantity of radiation that causes
diffuse redness over an area of skin after irradiation
Skin Erythema Dose
skin erythema dose required to affect 50% of those
irradiated (SED50) is about _____
5 Gyt (500 rad)
If epidermis is exposed to ____ doses, it will heal by regenerating
moderate
Skin damage extreme manifestations include:
atrophy fibrosis, changes in
pigmentation, ulcers, necrosis (tissue death), and cancer may occur
Hair follicles are ______
radiosensitive
Sebaceous and sweat glands are ______
radioresistant
loss of hair
Epilation
temporary hair loss
Alopecia
Threshold dose (Gyt) of Early transient erythema
2
Threshold dose (Gyt) of main erythema
6
Threshold dose (Gyt) of temporary epilation
3
Threshold dose (Gyt) of permanent epilation
7
Threshold dose (Gyt) of moist desquamation
15
Potential Radiation Response illness order
- Early transient
- Main Erythema
- Temporary epilation
- Permanent epilation
- Moist desquamation
Early Effects on Skin
- Erythema
- Inflammation
- Dry Desquamation
- Moist desquamation
Late Effects on Skin
- Atrophy
- Fibrosis
- Hyper-/hypo-pigmentation
- Ulceration
- Necrosis
- Cancer
Effect on Accessory Structures of Skin
- Epilation
- Destruction of sweat and sebaceous glands
The lens of the eye contain ______ cells that may be damaged by radiation
radiosensitive
formation of cataracts due to radiation exposure
Radiation cataractogenesis
The threshold dose for radiation-induced cataracts is approx
_____,
at doses _____ all irradiated will develop
cataracts
200 rad (2 Gy), >700rad (7 Gy)
Human gonads are extremely ______
radiosensitive
In females, Doses as low as ___ have caused observable responses
10 rad
As gonads create ____
cells that control fertility and heredity, their response to
irradiation has been analyzed thoroughly
germ
doses as low as ____ may delay or suppress
menstration
100 mGy (10 rad)
In both male and females, approx 2 Gy (200 rad) results in
temporary infertility
In both male and females, approx 5 Gy (500 rad) results in
permanent sterility
In males, doses as low as ____ can reduce number of spermatozoa
100 mGy (10 rad)
consists of bone marrow, circulating
blood, and lymphoid tissue
hemopoietic system
the principal effect of radiation is a decrease in number of
blood cells in the circulating peripheral blood
Hematologic Effects
