Rad Bio: Unit 4 Exam

Early Effects of Radiation

Response in humans that occur immediately to within a few days or months from exposures; responses depend on the individual’s radiosensitivity, dose amount and dose rate

What dose response relationship does early effects of radiation follow?

Nonlinear threshold

What tissue reaction does early effects of radiation follow?

Deterministic/Non-stochastic

What is the minimum threshold dose to the whole body to produce death?

1 Gy

What is the minimum threshold dose to the whole body to produce hematologic depression?

0.25 Gy

What is the minimum threshold dose to a small field to produce skin erythema?

2 Gy

What is the minimum threshold dose to a small field to produce epilation?

3 Gy

Acute Radiation Syndrome

The sqeuence of events after high level radiation exposure that leads to death within days, weeks or months

What are the three syndromes of manifest illness?

Hematologic death, GI death and CNS death

What are the stages of acute radiation lethality?

Prodromal period, latent period, manifest illness and recovery or death

Prodromal Period

Acute clinical symptoms that occur within hours of exposure and continue up to a day or two; radiation sickness, NVD and reduction in WBC

Latent Period

Period of “apparent” well-being, doses from 1-5 Gy occurs within weeks and doses exceeding 50 Gy occurs within hours or less

Manifest Illness

Dose necessary to produce syndrome and survival time determine radiation lethality; clinical symptoms are classified into three syndromes: hematologic, GI and CNS

Recovery or Death Period

Near lethal doses occur at 2-3 Gy (recovery may occur months-years) or highly lethal doses of > 6 Gy (death occurs in days-weeks)

At what period does recovery or lethal effects begin to occur?

Latent period

What is hematopoietic syndrome characterized by?

Destruction of bone marrow, inadequate blood cell production and decrease in RBC, WBC and platelets

Hematopoietic System

Consists of bone marrow, circulating blood and lymphoid tissue/organs; all cells of this system develop from the same type of stem cell (pluripotential)

Stem cells of the hematopoietic system can develop into what mature cells?

Lymphocytes, granulocytes, thrombocytes and erythrocytes

Lymphocytes

Produced at varying times, have shortest lifespan of all blood cells

Granulocytes

Takes 8-10 days to be produced, last a couple of days

Thrombocytes

5 days to produce, lasts 1 week to 1 month

Erythroytes

8-10 days to be produced, lasts 4 months

Cell Renewal System

Hematopoietic stem cells can replenish themselves through self-renewal

What is a lymphocytes response to radiation?

1st cells to become affects, reduction in number occurs within minutes, hours or up to several months

What is a granulocytes response to radiation?

Rapid increase, then rapid decrease, then a slower decrease; occurs within 15-20 days, recovery takes several months

What is a thrombocytes response to radiation?

Deplete slowly, reach a minimum in 30 days, recovery takes 6 months to a year

What is an erythrocytes response to radiation?

Less sensitive than other blood cells, occurs within several weeks, recovery takes 6 months to a year

What is the approximate dose for hematologic syndrome?

1-10 Gy

What is the prodromal period of hematologic syndrome?

Mild sickness

What is the latent period of hematologic syndrome?

Wellness up to 4 weeks

What is the manifest illness period of hematologic syndrome?

NVD, malaise, fever and infection

What are the most radiosensitive cells of the body?

Lymphocytes and spermatogonia