Early Effects

What are the 4 determinants of radiation damage in the body?

1. LET

2. RBE

3. OER

4. Cell differentiation (metabolic state)

What is the term for the biologic damage to the exposed individual?

Somatic

What is another term for a deterministic reaction?

Non-stochastic

What is another term for a probabilistic reaction?

Stochastic

Which reaction is dose dependent - i.e., has a threshold dose?

Non-stochastic (determined by threshold dose)

What happens to the biologic effect as dose increases with a non-stochastic reaction?

Effect severity increases with dose

What is the most common early (acute) non-stochastic biologic response to radiation?

Erythema (diffuse skin redness)

What is the meaning of epilation and what is another term for this effect?

Loss of hair - alopecia

What is the term for shedding the outer skin layer due to irraadiation?

Desquamation (dry or moist)

What happens to the biologic effect as dose increases with a stochastic reaction?

Dose increase = probability that effect will occur increases

What is the most common late (chronic) Stochastic biologic response to radiation?

Cancer

Why is there no early Stochastic somatic biologic response to irradiation?

Not enough time for the probability of effect occurrence to build

What is the term for the late genetic response to radiation?

Mutagenesis (future offspring)

What are the 5 requirements for exposure to be classified as Acute Radiation Sickness (ARS)?

1. Large dose

2. Whole body

3. Short time

4. External

5. Penetrating

What human populations serve as study sources for the effects of ARS?

1. Hiroshima/Nagasaki survivors

2. Chernobyl

3. Marshall islanders

4. Radiation therapy patients

What are the 3 syndromes of ARS?

1. Hematopoietic (bone marrow)

2. Gastrointestinal

3. Cerebrovascular

What are the 4 stages of each ARS syndrome?

1. Prodromal

2. Latent

3. Manifest Illness

4. Recovery/death

What is the threshold dose for Acute Radiation Sickness (ARS)?

1 Gy whole body

What does NVD stand for when referencing the ARS prodromal stage?

Nausea, vomiting, diarrhea

What is the typical biologic response if the threshold dose of ARS is not reached?

Hematologic depression (low blood counts)

Is ARS considered a stochastic or non-stochastic dose response?

Non-stochastic (deterministic - has threshold dose of 1 Gy)

What is the term for an abnormal decrease in white blood cells?

Leukopenia

What is the normal white blood cell count?

5,000-10,000 per mm^3 blood

What is the normal platelet count for adults?

150,000-450,000 per μl of blood

What is the exposure dose range for the Hematopoietic Syndrome of ARS?

1-10 Gy whole body

Which body tissues (exposures) are included in the Hematopoietic Syndrome?

1. Bone marrow

2. Circulating blood

3. Lymph nodes

4. Spleen

5. Thymus

What is the term for a decrease in red blood cells, white blood cells, and platelets?

Pancytopenia

What is the latent period for Hematopoietic Syndrome?

1-6 weeks

What is the average survival time for Hematopoietic Syndrome?

6-8 weeks with whole body dose of 2+ Gy

What would increase the average survival time for Hematopoietic Syndrome?

1. Antibiotics

2. Sterile environment

3. Blood transfusion

4. Bone marrow transplant

What is the cause of danger or death for Hematopoietic Syndrome?

Infection (low WBC) & Hemorrhage (low platelet count)

What is the standard fractionated & protracted dose for radiation therapy?

2 Gy per day over 4-6 weeks

What is the threshold dose for the Gastrointestinal Syndrome of ARS?

6 Gy whole body (range of 6-10 Gy whole body)

What is the cause of death for Gastrointestinal Syndrome?

1. Electrolyte imbalance

2. Emaciation

3. Dehydration

What is the average survival time with Gastrointestinal Syndrome?

1. 3-10 days

2. Survival time does not change with dose

What is the term for the erosion of intestinal epithelial cells?

Denudation

Which part of the GI tract is most affected by the Gastrointestinal Syndrome of ARS and why?

1. Small intestine

2. Villi eroded & cannot provide surface area for nutrient absorption

Which human population most likely died from Gastrointestinal Syndrome after radiation exposure?

Chernobyl workers

What is the average survival time for Cerebrovascular Syndrome?

Hours to 3 days (no recovery)

What is the exposure range for Cerebrovascular Syndrome?

50+ Gy whole body

What is the latent period for Cerebrovascular Syndrome?

12 hours

What are some of the manifest symptoms of Cerebrovascular Syndrome?

1. Increased severity of NVD (prodromal)

2. Shock

3. Ataxia (Confusion & loss of muscle coordination)

4. Seizures

5. Respiratory distress

6. Coma

7. CSF leakage

8. ICP

9. No recovery from this syndrome

What is the term for confusion & loss of muscle coordination after a large radiation exposure?

Ataxia

What is the term for organ and/or tissue shrinkage after a high dose of radiation?

Atrophy

What is the cause of death from Cerebrovascular Syndrome according to the CDC?

Collapse of circulatory system & ICP from edema/vasculitis/meningitis

According to the CDC, what is the term for transient erythema and reddening/blistering/ulceration of the skin after radiation exposure?

Cutaneous Radiation Syndrome (CRS)

A single absorbed dose of 2 Gy from a fluoroscopy exam can cause radiation-induced skin erythema in how many hours?

24-48 hours

What is LD 50/30?

Radiation dose lethal to 50% of the population in 30 days

Why is LD 50/60 more accurate for humans?

Human cell division is closer to average 60 days rather than 30 days

According to this LD 50/30 curve, a human could receive up to what dose with no deaths?

Threshold dose of 1 Gy

Who was the dentist who first advocated for radiation protecting by suggesting beam filtration, collimation, & lead tube housing?

Wililam Herbert Rollins

What is the term for low voltage x-rays historically used to treat skin conditions like ringworm?

Grenz rays

What is the term for higher voltage x-rays used in radiation therapy?

Orthovoltage

What is the term for a genetic mutation in future generations due to irradiation of parental gonads prior to conception?

Mutagenesis

Which are more radiosensitive - sperm or ova?

Sperm - constantly reproducing

What is the term for the reduction of spermatogonia leading to a decreased sperm count?

Maturation Depletion

How much radiation dose to cause temporary sterility in males & females and/or possible genetic effects?

1. 2 Gy

2. 42 minutes normal fluoro, 6 minutes cine

How much radiation dose to cause permanent sterility in males & females?

5-6 Gy

How much radiation dose to suppress menstruation, depress sperm population, or decrease lymphocytes?

0.1 Gy

What is the term for decreased RBC count?

Anemia

What is considered a safe dose of radiation?

No radiation dose is considered safe

What 4 factors determine radiation damage?

1. Quantity of exposure

2. Ability to ionize (LET)

3. Amount of exposed area (Collimation or DAP)

4. Body part radiosensitivity

What is Somatic radiation damage?

1. Biologic damage to the exposed individual

2. Cannot be passed to offspring

3. Cancer, skin burns, cataracts, radiation sickness

What is Genetic (Hereditary) radiation damage?

1. DNA mutations of reproductive (germ) cells

2. Can be passed on to future generations from an exposed individual

3. Increased risk of genetic disease in offspring when parental gonads are irradiated (damage expressed at birth of child)

4. Congenital abnormalities - present at birth

5. Also called hereditary radiation effects

What is Teratogenic radiation damage?

1. Substance or condition that can cause birth defects or abnormal fetal development if exposed in utero

2. Irradiation of the fetus in utero

What is Non-stochastic?

1. Deterministic

2. Determined by threshold dose

3. Effect severity increases as the dose increases

What is Stochastic?

1. Probabilistic

2. No threshold dose (not dose dependent)

3. As dose increases, the probability/chance of occurrence that effect will occur increases

When do Early Non-stochastic Effects appear?

1. Acute

2. Minutes, hours, days, weeks

Are early non-stochastic effects reversible?

May be reversible

What do early Non-stochastic effects do damage to?

Parenchymal cells

What is Erythema?

Diffuse skin redness

What is Epilation?

Loss of hair

What is Desquamation?

Shedding of outer skin layer

What is ARS?

Acute Radiation Syndrome

When are late non-stochastic effects seen?

Months, years

Are late non-stochastic effects reversible?

No, irreversible

What are the 5 conditions for ARS?

1. Large dose

2. Whole body

3. Short time

4. External

5. Penetrating radiation

What are ARS populations?

1. Hiroshima & Nagasaki (WWII)

2. Marshall Islanders (atomic bomb testing by U.S.)

3. Chernobyl

4. Radiation therapy patients

What are 3 ARS syndromes?

1. Hematopoietic

2. Gastrointestinal

3. Cerebrovascular

What is the threshold dose for ARS?

1 Gy whole body dose

What are the 4 stages of each ARS syndrome?

1. Prodromal

2. Latent

3. Manifest illness

4. Death or recovery

What symptoms are seen in the Prodromal stage?

1. NVD

2. Leukopenia

What is Leukopenia?

Abnormal decrease in WBCs

What is the normal WBC adult count?

5,000-10,000/mm^3 blood

What is symptom severity dependent on in the Prodromal stage?

Symptom severity is dependent on dose

What are the Latent stage symptoms?

No visible symptoms

What is the time period for the Latent stage?

Generally healthy, recovery or lethality begins

What is the Manifest Illness time period?

Hours to months (depends on dose)

What are the Manifest Illness stage symptoms?

Specific to syndrome (hematopoietic, gastrointestinal, cerebrovascular)

What is the Death or Recovery time period?

Several weeks to 2 years

What is Hematopoietic Syndrome also known as?

Bone Marrow Syndrome

What are the Hematopoietic Syndrome targets?

1. Marrow

2. Circulating blood

3. Lymph nodes

4. Spleen

5. Thymus

What is the Hematopoietic Syndrome dose range?

Whole body 1-10 Gy (100-1000 rads)

How is Hematopoietic Syndrome damage reflected?

Damage reflected when circulating end cells die & aren't replaced (decreased counts)

What is the Hematopoietic Syndrome latent period timeline?

1-6 weeks

What is Pancytopenia?

Decrease in RBCs, WBCs, and platelets

What is the normal adult platelet count?

150,000 to 450,000/mm^3 blood

What is Hematopoietic Syndrome death due to?

Infection & hemorrhage

What is the average surbibal time of Hematopoietic Syndrome?

6-8 weeks with 2+ Gy

What is the standard fractionation dose?

2 Gy/day over 4-6 weeks