Radiation Biology pt. 2 Flashcards
Fukushima Daichi,
March 11, 2011
An 8.9 magnitude earthquake and subsequent tsunami
overwhelmed the cooling systems of an aging reactor along
Japan’s northeast coastline. The accident triggered
explosions at several reactors at the complex, forcing a
widespread evacuation in the area around the plant
San Onofre Nuclear Power Plant, San Diego County
San Onofre is at the northwest
corner of San Diego County and
is surrounded by Camp
Pendleton and San Onofre
State Park. Interstate 5 passes
right by.
ACUTE RADIATION SYNDROME
(2)
- A collection of signs and symptoms
following acute whole-body radiation
exposure - Information derived from animal
experiments, patient therapeutic
radiation exposures, atomic bombings
and radiation accidents.
ACUTE RADIATION SYNDROME
* Sub-lethal exposure
* Lethal exposure
* Supralethal exposures
< 2 Gy (200 Rads)
~ 2 –8 Gys (~ 200 to 800 Rads)
> 8 Gys (800 Rads)
Higher dose, — latent period and —
onset of severe symptoms
shorter
rapid
Acute radiation syndrome
periods (4)
- Prodromal period
- Hematopoietic syndrome
- Gastrointestinal syndrome
- Central nervous system and
cardiovascular syndrome
(CNS/CVS syndrome)
- Prodromal period
(<200 R; <2Gy)
- Hematopoietic syndrome
(200- 1,000R; 2-10 Gy)
- Gastrointestinal syndrome
(1,000 – 10,000R; 10 – 100 Gy)
- Central nervous system and
cardiovascular syndrome
(>10,000R; >100 Gy)
PRODORMAL SYNDROME
- Shortly after exposure to whole-body
radiation, an individual may develop
nausea; vomiting;
diarrhea; anorexia;
Causes general malaise, fatigue,
drowsiness and listlessness
Symptoms resolve after several weeks
ACUTE RADIATION SYNDROME
Lethal exposure range
Supralethal exposures
~ 2 – 8 Gys
(~ 200 to 800 Rads)
> 8 Gys
(> 800 Rads)
short latent period and rapid onset of severe symptoms
HEMOPOIETIC SYNDROME
- irreversible injury to the proliferative
capacity of the spleen and bone
marrow with loss of circulating
peripheral blood cells
HEMOPOIETIC SYNDROME
* infection from the
(2)
lymphopenia and
granulocytopenia
* hemorrhage from thrombocytopenia
* anemia from the erythrocytopenia
* Death within 10 - 30 days.
GASTROINTESTINAL SYNDROME
(2)
- extensive damage to the GI system (in
addition to the hemopoietic system) - There is extensive injury to the rapidly
proliferating basal epithelial cells of the
intestinal villi which leads to atrophy and
ulceration.
GASTROINTESTINAL SYNDROME
(5)
- loss of plasma and electrolytes
- hemorrhage and ulceration
- diarrhea, dehydration, weight loss
- Infection
- Death in 3 - 5 days
CARDIOVASCULAR
and
CENTRAL NERVOUS SYSTEM
SYNDROME
(3)
- radiation induced damage to neurons and fine vasculature of brain
- Intermittent stupor, incoordination, disorientation, and convulsions from extensive CNS damage
- irreversible damage with death in a few minutes to 48 hours.
RADIATION TREATMENTS TO THE
ORAL CAVITY
- Combined surgical, radiation and chemotherapy
often provides the optimum treatment
RADIATION TREATMENTS TO THE ORAL
CAVITY
* Oral tissues are subjected to high doses of
radiation during the treatment of malignant
tumors of the (5)
soft palate, tonsils, floor of the
mouth, nasopharynx, and hypopharynx
RADIATION TREATMENTS TO THE ORAL
CAVITY
* Total radiation doses to treat malignant
tumors ranges from
6,000 - 8,000 Rads. Or
60 -80 Gy
Previous Radiation Therapy for Cancer
* Dose
– Solid tumors =
– Lymphomas =
– Intraoral cancer =
- 1 Gy =
60 –80 Gy
20 –40 Gy
50 Gy
1 million μSv
Single intraoral — μSv
FMX (20 images) — μSv
Panoramic radiograph — μSv
1.3
35
9
RADIATION TREATMENTS TO THE ORAL
CAVITY
* Fractionation of the total dose into multiple
small doses provides
greater tumor destruction
than a single large dose
* Fractionation also increases cellular repair of the
normal tissues
Mucosa: -
mucositis
- 20 infections
Taste Buds: -
loss of taste
Salivary Glands: -
xerostomia
Teeth:
- lack of or retarded development
- radiation caries
Bone: -
osteoradionecrosis
Muscle: -
fibrosis
Hypoguesia
(2)
- Epithelial atrophy,
xerostomia and
mucositis all result in
loss of taste
(hypoguesia) by the 2nd - 3rd week of treatment
- recovery of taste
sensitivity will occur in
2 - 4 months following
treatment
SALIVARY GLANDS
There is marked and
progressive loss of
salivary secretion
Adult teeth are very resistant to the
direct
effects of radiation exposure
There is no discernible effect on the
crystalline
structure of enamel, dentin, or cementum
Radiation does not increase the —- of
teeth
solubility
When teeth are irradiated during the
developmental stage, their growth may be
severely retarded
If the radiation precedes calcification, the
tooth bud may be
destroyed
Irradiation after initiation of calcification,
teeth may demonstrate
malformations and
arresting general growth
Generally, if some portion of the salivary gland
has been spared, the dryness of the mouth
subsides in
6 month to 1 yeAR
However, xerostomia may persist without any
significant return of salivation
Major salivary glands are often exposed
unavoidably to radiation during
treatment
for carcinoma of the oral cavity or
oropharynx
Parenchymal cells (especially of the parotid
glands) are very sensitive to X-rays and are
replaced by
fibrosis and adiposis with
parenchymal degeneration and loss of fine
vasculature
The scanty saliva makes the mouth
dry
(xerostomia) and tender. Swallowing is difficult
and painful
The residual saliva has a lowered pH (from 6.5
to 5.5), which is acidic enough to initiate
decalcification of enamel
The buffering capacity of saliva is reduced
40 -
45%
Children may show defects in the permanent
dentition, such as
retarded root development,
dwarfed teeth, or failure to form one or more
teeth
A dose as low as 200 R at the age of 5 months
has been reported to cause
hypoplasia of the
enamel.
Although irradiation may retard or abort tooth
formation, the — mechanism is much
more radiation resistant
eruptive
Irradiated teeth with —
will still erupt
altered root formation
RADIATION CARIES
* A rampant form of decay that
may affect
individuals who received a course of
radiation therapy that include exposure of
the salivary glands
BONE
Osteoradionecrosis
The primary damage to bone is from
irradiation to
(2)
– fine vasculature
– marrow –affecting vascular and hemopoietic
elements.
Radiation Effects –Oral Tissues
– Musculature
* Inflammation and fibrosis –results in
contracture and
trismus in the muscles
