Radiation Biology: Ch. 8

threshold:

the point at which a response or reaction first occurs

non-threshold:

no radiation exposure is absolutely safe

linear:

implies biologic response to radiation is directly proportional to dose received

non-linear:

more of a S-shaped response on a graph

defined as biologic damage sustained by living organisms as a consequence of exposure to ionizing radiation

somatic effects

effects are cell killing and directly related to dose received, have a threshold

early somatic tissue reactions

when will early tissue reactions occur

within minutes, hours, days, or weeks

some examples of early tissue reactions

• nausea

• fatigue

• erythema

• epilation

• blood disorders

• intestinal disorders

• fever

• depression of sperm count

• temporary for permanent sterility

• injury to CNS

• dry and moist desquamation

occurs when the whole body is exposed to large doses of radiation over a short period of time

Acute Radiation Syndrome

what are the three dose related syndromes or conditions with ARS

hematopoietic syndrome

gastrointestinal syndrome

cerebrovascular syndrome

four mainstages of ARS, in order

1. prodromal stage

2. latent period stage

3. manifest illness stage

4. recovery or death

occurs within hours after a whole body absorbed of 1 Gyt or more

prodromal stage

symptoms of the prodromal stage

nausea, fatigue, diarrhea, vomiting, leukopenia

approx. 1 week during which no visible symptoms occur, is often mistaken for early recovery, but is actually during this period when recovery or lethal effects occur

latent period

towards the end of the first week of the latent period, this phase begins, symptoms become visible

manifest illness stage

manifest illness symptoms

• apathy

• confusion

• epilation

• headaches and exhaustion

• vomiting, severe diarrhea

• fever and infection

• decrease in red and white blood cells

• hemorrhage

• cardiovascular collapse

follows the third stage, emaciated humans eventually die, may be days or weeks

recovery or death

after what dose, during the recovery or death stage, may occur within 3-6 months

2-3 Gyt

approx. ___% of damage is irreparable

approx. ___% may be repaired over time

10%

90%

also known as bone marrow syndrome, and occurs with dose ranging from 1-10Gyt

hematopoietic syndrome

is the most radiosensitive vital organ system, symptoms appear in a matter of a few hours and may persist for several days

hematopoietic system

seen only in the hematopoietic syndrome, recovery is ________

dose dependent

hematopoietic syndrome-death may occur as late as how many weeks

6-8 weeks

appears at a threshold of approx. 6 Gyt, and peaks after 10 Gyt

gastrointestinal syndrome

GI syndrome usually results in death after how long

3-10 days

GI syndrome symptoms

• severe nausea

• vomiting

• diarrhea and cramping

• fever

• fatigue and lethargy

• loss of appetite and weight loss

• anemia

• leukopenia

• hemorrhage

• infection

• electrolyte imbalance

• emaciation

why does GI syndrome death occur so quickly

survival time does not vary with this syndrome, death occurs primarily because of catastrophic damage to the epithelial cells that line the GI tract

what specifically does a person die from because of GI syndrome

combination of infection, fluid loss or electrolyte imbalance

uncontrolled passage of fluids across the intestinal membrane when lining is stripped of functional cells

results from receiving 50.0Gyt, or more and can cause death within a few hours to 2-3 days.

cerebrovascular syndrome/CNS syndrome

prodromal stage CNS syndrome symptoms

• excessive nervousness, confusion

• severe N,V,D

• loss of vision

• burning feeling to skin

• loss of consciousness

how long does the latent period last following the prodromal stage during CNS syndrome

latent period lasting up to 12 hours

manifest stage symptoms during CNS syndrome

• disorientation and shock

• periods of agitation altering with stupor

• ataxia

• edema in the cranial vault

• loss of equilibrium

• fatigue and lethargy

• meningitis

• vasculitis

• coma

what causes failure of the central nervous system and cardiovascular systems

injured blood vessels and capillaries permit fluids to leak into the brain causing increased intra-cranial pressure which causes tissue damage

final result of CNS syndrome

failure of the CVS and CNS systems which results in death in a matter of minutes

in which syndrome does failure of the GI and hematologic systems occur, but is never presented because of death occurring so quickly

CNS syndrome

Bushong:

as body rad-dose increases, the average time between exposure and death decreases

what are the distinct regions that are associated with the 3 radiation syndromes in order

1. hematologic death

2. gastrointestinal death

3. central nervous system death

serial measurements of levels of lymphocytes and granulocytes in blood and quantitative analysis of dicentric chromosomes and hematopoietic cells coming from active bone marrow

biologic dosimetry

what is biologic dosimetry used to measure

exposure after nuclear accidents and other radiation mishaps

lethal dose definition:

50/30 is defines as the whole body dose of radiation which can be lethal to 50% of the pop. within 30 days

what is the LD 50/30 for human adults

3-4 Gyt (without medical support)

anything greater than 8 Gyt is considered a LD of ____

100/30

why may LD 50/60 be more accurate for a measure of human survival

it includes all persons who may die from the hematopoietic syndrome

when may repair and recovery occur

when cells are exposed to sublethal dose, cells will divide and repopulate-regain most ability

what kinds of cells are more severely damaged

oxygenated

significant cell death usually results, leading to the shrinkage of organs and tissues

atrophy

organ/tissue response to radiation exposure depends on what factors

• radiosensitivity

• reproductive characteristics

• growth rate

which types of tissues suffer immediate consequences

skin, reproductive organs, bone marrow

significant reddening of the skin caused by exposure to radiation that eventually led to cancerous lesions on the hands and fingers of early radiologists

radiodermatitis

who was the dentist that became the first known advocate for rad procedures

William Herbert Rollins

what were William Herbert Rollins three importances

war radiopaque eyewear

enclose x-ray tube in housing

covering area of interest

outer layer of skin:

epidermis

middle layer of connective tissue:

dermis

layer of fat and connective tissue:

hypodermis

skin is radiosensitive or radio insensitive?

radiosensitive

what dose can cause radiation induced skin erythema within 24-48 hours of exposure

2 Gyt

shedding of the outer layer of skin occurring at higher radiation doses

usually begins as moist and then may develop into dry sensation

desquamation

epilation:

hair loss (alopecia)

historically, how were skin diseases treated

grenz rays, x-rays in the energy range of 10-20 kvp

exposure rates that may cause radiation burns

HLCF for extended periods, ranging from 100-200 mGya/min

doses as low as ___ can depress the sperm pop., delay or suppress menstruation, and has potential to cause genetic mutations in future generations

0.1 Gyt

consist of bone marrow circulating blood, and lymphoid organs

hematopoietic system

what do cells of the hematopoietic system develop from

single pluripotential stem cell

defined as the study of cell genetics with an emphasis on cell chromosomes

cytogenetic effects

occur when irradiation occurs early in interphase, before DNA synthesis takes place

chromosome aberrations

occurs if irradiated later in interphase, after DNA synthesis

chromatid aberrations