Rad Safety Exam 3: Deterministic Effects

What are some examples of deterministic effects?

Skin reddening (erythema), cataracts, and acute radiation syndrome.

What are some examples of stochastic effects?

Cancer and genetic effects

Acute radiation syndrome is defined by... and only occurs during what kind of exposures?

..receiving a radiation dose over a short period of time.

It only occurs during whole body exposures. Mainly limited to external exposure and not so much internal exposure.

What are the three levels of Acute Radiation Syndrome?

1. Hematopoietic syndrome which affects blood producing organ

2. Gastrointestinal syndrome

3. Central nervous system syndrome

What is the dose range for hematopoietic syndrome? What symptoms happen here?

0.3 Gy to 10 Gy. Nausea, vomiting, drop in blood cell counts.

What is the dose range for GI syndrome? What symptoms happen here?

10 Gy to 50 Gy. Severe nausea, vomiting, cramps, and diarrhea.

What is the dose range for Central Nervous system syndrome? What symptoms happen here?

>50 Gy. Confusion, loss of consciousness, severe vomiting and diarrhea

What is the dose range for LD50/60?

2.5-5 Gy

What are the 3 stages of ARS?

Prodromal phase, latent phase, and manifest phase

What happens in each of the 3 stages of ARS: Prodromal, Latent, and Manifest?

Prodromal: Initial stage of radiation symptoms like vomiting, diarrhea, anorexia, and erythema.

Latent: Cells begin to repair themselves and reproduce to take over for dead cells.

Manifest: Culmination of cell death can lead to complications such as infection, organ failure, dehydration, etc.

In the prodromal stage of ARS, the higher the dose received the _______ the onset of symptoms.

quicker

In the latent stage of ARS, the higher the dose the ________ the latent phase.

shorter (because repair would not be happening much)

The Law of Bergonie and Tribondeau states that radiosensitivity is proportional to what and inversely proportional to?

Proportional to its mitotic activity

Inversely proportional to its degree of differentiation (less specialized a cell is, the more sensitive it is to radiation)

Stem cells are _____ radiosensitive

more (because they are fully undifferentiated

Oxygen Effect or Oxygen Enhancement Ratio

Increasing the amount of oxygen in a cell makes it more susceptible to damage from indirect radiation damage (free radicals)

Which radical becomes more prevalent as the oxygen content of cells increases?

Superoxide (O2)

Dose received over a long period of time is considered _______ _____

Chronic dose

Death can occur from an acute dose as low __ Gy, but requires _______ in one week, __________ over 1-3 month period.

1 Gy, 4-8 Gy, 10-14 Gy

Chronic dose is more often associated stochastic effects or deterministic effects?

Stochastic effects, but high enough chronic doses can lead to deterministic effects.

Delayed effects are...?

Deterministic effects that can manifest months to years after a radiation exposure.

What is the most common localized effect and at whose dose can it occur?

Skin erythema, 2 Gy

What is the threshold for necrosis, where skin turns black and dies, to occur?

20-30 Gy

Temporary sterility for men and women can occur at what doses?

0.15 Gy for men and 0.65-1.5 Gy for women

Cataracts can form around ____ Gy

2

What is the permanent sterility threshold dose for testes? ovaries? (range)

3.5-6 Gy

2.5-6 Gy

What are some ways to treat acute radiation dose?

Antibiotics since depletion of WBC leads to increased risk of infection. Blood transfusions to increase WBC count.

Skin damage treated with topical analgesic/antibiotics. Amputation for gangrene in extreme cases.

Is there effective treatment past hematopoietic syndrome?

No

The LD50/60 for people who receive treatment is 5-7 Gy, and possibly up to 9 Gy when they are given immediate medical care. What is the threshold for no recovery, even with medical care?

10 Gy

What evidence do we use to make inferences about teratogenic effects?

Evidence from atomic bomb survivors, although exact threshold doses are hare to pin down

What is the most sensitive stage of embryonic development due to high stem cell concentration and rapid growth?

Pre-implantation (0-2 weeks after conception)

What is the all or nothing response during pre implantation exposure?

The embryo will either die or have no detectable birth defects if it is not killed.

What is the stage of embryonic development that is less sensitive than preimplantation and where damage generally leads to birth defects?

Organogenesis (2-15 weeks after conception)

What is the most common symptom of exposure during the organogenisis stage of embryonic development?

Microcephaly, seen around 150-250 mGy

What are the main symptoms of radiation exposure from weeks 15 to the end of pregnancy? What is this stage called?

Growth retardation, decreased intellectual capacity, and cancer risk. This is the fetal growth stage.

What is the least sensitive stage of fetal development and why?

Fetal growth stage because of lower stem cell concentration.

What is the threshold for severe intellectual disability in the fetal growth stage? What is the threshold for death?

500 mGy for intellectual disability.

>2Gy for death.

Per regulations, what is the maximum dose to a fetus over the entire pregnancy? (aka Fetal Radiation Dose)

500 mrem