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

What is the approximate dose of GI syndrome?

10-50 Gy

What is the prodromal period of GI syndrome?

NVD

What is the latent period of GI syndrome?

3-5 days of wellness

What is the manifest illness of GI syndrome?

2nd wave of NVD with loss of appetite, lethargy and shock

What is CNS syndrome characterized by?

Damage to cerebrovascular structure with the brain, damage to blood vessels resulting in fluid leaking into brain, increased intracranial pressure and tissue damage

What is the approximate dose of CNS syndrome?

> 50 Gy

What is the prodromal period of CNS syndrome?

Severe NVD

What is the latent period of CNS syndrome?

Can last up to 12 hours

What is the manifest illness period of CNS syndrome?

Prodromal symptoms return more severely

CNS Syndrome

Increased intracranial pressure, vasculitis and meningitis; ultimate cause of death is elevated fluid in the brain

Mean Survival Time

Average length of time from exposure that half of those exposes are still alive

What is the most sensitive system?

Hemopoeitic

GI syndrome is characterized by destruction of:

Epithelial and villi cells

What is the most sensitive part of the GI tract?

Small bowel

Average survival time for hematologic

2 to 8 weeks

Average survival time for GI

3 to 10 days

Average survival time for CNS

0 to 3 days

What manifestion of ARS has the highest dose threshold?

CNS

What manifestion of ARS has the lowest dose threshold?

Hematologic

What whole body dose will cause death to an entire population in 30 days without medical support?

> 6 Gy

LD x/y

What is x?

% of population expected to die

LD x/y

What is y?

Number of days to measure

LD 50/30

The dose of radiation to the whole body that causes 50% of the subjects to die within 30 days

What dose response relationship does LD 50/30 follow?

Nonlinear threshold

What LD is more accurate and meaningful for humans?

LD 50/60

What LD is more commonly used with animals?

LD 50/30

What is the human dose for LD?

3-4 Gy

When and where did the goiania accident occur?

Brazil, 1987

Who was the individual affected in the Tokaimura Accident?

Hisashi Ouchi

Who was the first known advocate for radiation exposure protection due to his own experience with radiation burns?

William Rollings

What layer of skin contains the sensitive stem cells?

Basal layer of epidermis

What dose causes skin erythema?

2 Gy

What dose causes epilation?

3 Gy

SED50

The dose required to affect 50% of those irradiated is approximately 5 Gy

What other skin disease was treated with low kVp x-rays causing hair loss?

Ringworm

Early effects on the skin are more likely to occur from procedures in what 3 advanced imaging modalities?

IR, cath lab and radiation therapy

What do ovaries produce?

Oogonia

What do testes produce?

Spermatogonia

Gametogenesis

The process of oogonia and spermatogonia maturing into ovum and sperm

Oocytes

Encapsulated oogonia

How many ova are available for fertilization?

400-500

How long does the maturation process for sperm take?

3-5 weeks

What dose causes suppression and delay of menstruation, sperm reduction and atrophy?

.1 Gy

What dose to the gonads causes temporary infertility?

2 Gy

What dose to the gonads causes permanent sterility?

5 Gy