RAD 208 EVERYTHING

Radiation-induced damage at the cellular level may lead to measurable somatic and hereditary damage in the living organism as a whole later in life.

Late effects (Stochastic)

Examples of measurable late biologic damage

Cataracts

Leukemia

Genetic mutation

When do late somatic effects typically appear?

appear months or years after such exposure

Effects may result from

Previous whole- or partial-body acute exposure

Previous high radiation doses

Long-term low-level doses sustained over several years

science that deals with the incidence, distribution, and control of disease in a population and consist of observations and statistical analysis of data

Epidemiology

Epidemiologic studies are of significant value to radiobiologists who use the information from these studies to…

formulate dose–response estimates to predict the risk of cancer in human populations exposed to low doses of ionizing radiation.

Radiation dose–response relationship is demonstrated
graphically through a curve that maps the observed effects of radiation exposure in relation to the dose of radiation received

Dose–Response Curves

Which of the following is illustrates the relationship between exposure to ionizing radiation and possible resulting biologic responses?

Dose-response curve

Which radiation dose-response is said to be more accurate of stochastic somatic and genetic effects at low-dose
levels from low-LET radiation.

linear-quadratic nonthreshold curve (LQNT)

Which is the radiation dose-response that is used for most cancer types and stochastic effects?

linear nonthreshold

Indicates that a radiation absorbed dose of any magnitude has the capability of producing a biologic effect. No “safe” dose

Nonthreshold

LNT curve implies that the biologic response to ionizing
radiation is…to the dose received

Directly proportional

The linear, nonthreshold curve implies that biological response is:

Directly proportional to the dose

What type of dose-response curve is used to predict
probabilistic effects?

Linear, nonthreshold

linear dose–response model for radiation protection standards has the potential to exaggerate the seriousness of radiation effects at

lower dose levels from low-LET radiation

The use of a linear dose-response model accurately reflects the effects of what type of radiation and dose?

high-LET radiation (neutrons and alpha rays) at higher doses

Regulatory agencies have chosen to be conservative by using a model that may overestimate risk of radiation but is not

underestimate risk

a point at which a response or reaction to an increasing
stimulation first occurs (means that below a
certain radiation level or dose, no biologic effects are observed)

Threshold

Biologic effects begin to occur only when what is reached?

threshold or dose

Acute reactions from significant radiation exposure such as skin erythema and hematologic depression may be demonstrated graphically through the use of…

Linear threshold dose-response curve

Generally employed in radiation therapy to demonstrate high-dose cellular response to the radiation absorbed within specific locations, such as skin, lens of the eye, and various types of blood cells

Sigmoid or S-shaped (nonlinear) Threshold curve

What does the tail of the curve in a sigmoid threshold indicate?

limited recovery occurs at lower radiation doses

In a sigmoid curve At the highest radiation doses, the curve gradually levels off and then veers downward because the affected living specimen or tissue does what?

Dies

The probability that the effect happens depends upon the
received dose, but the severity of the effect does not

Stochastic effect (you won’t be getting a worst cancer cause of a higher dose)

Both the probability and the severity of the effect depend upon the dose.

Tissue reactions

Major types of late effects

Carcinogenesis

Cataractogenesis

Embryologic effects (birth defects)

Carcinogenesis is also known as what? and what is it?

Also known as tumorigenesis. It’s the formation of cancer

what is the most significant late stochastic effects caused by exposure to ionizing radiation

Cancer

Why is the risk estimate for humans contracting cancer from low-level radiation exposure is still controversial?

No conclusive proof exists that low-level ionizing
radiation exposure below 0.1Gy causes a significant
increase in the risk of malignancy

Why is Cancer caused by low-level radiation difficult to identify

physical appearance of cancer induced by ionizing radiation does not appear different than a cancer caused by
other agents

Where does evidence from radiation carcinogenesis comes from ?

Epidemiologic studies conducted many years after subjects
were exposed to high doses of ionizing radiation

Both models predict the number of excess cancers, or cancers that would not have occurred in the population in question without the exposure to ionizing radiation

Absolute risk or Relative risk

Epidemiologic data about the Hiroshima atomic bomb survivors Indicate the chance of contracting leukemia as a result of exposure to radiation is…to the magnitude of the radiation exposure

Directly proportional

Radiation-induced leukemia is assumed to follow a….compared with leukemia in a population that has not been exposed to ionizing radiation

linear non-threshold dose–response relationship

Which of the following dose-response relationship represents radiation- induced leukemia and genetic effects?

Linear, nonthreshold

There is a high probability that a single dose of how much will induce the formation of cataracts?

2Gyt

The results of Cataractogenesis is?

Partial or complete loss of vision

Radiation-induced cataracts in humans follow what type of relationship?

threshold, nonlinear dose–response relationship

What is the amount of radiation in a fertilized ovum that will cause embryonic death?

0.05 Gyt to 0.15 Gyt

How much radiation will result in fetal death or sever congenital abnormalities during the Organogenesis Stage (first 12 wks)?

200mSv (20rem)

What are some sever congenital abnormalities?

Growth inhibition

Intellectual disabilities

Genital deformation

Sensory organ damage

Fetal radiosensitivity decrease as the…

gestation progresses

Radiation-induced damage to the DNA molecule in the sperm or ova of an adult may result in…

various diseases or malformations and transmitted to successive generations

The radiation dose that causes the number of spontaneous mutations occurring in a given generation to increase to two times their original number

Doubling dose

The radiation doubling equivalent dose for humans is estimated to have a mean value of

1.56 Sv

Cancer and genetic defects are examples of:

Stochastic effects

Late effect of radiation, whose incidence is dose related and for which there is no threshold dose, are called

Stochastic/probabilistic

Biologic effects of radiation that occur relatively soon after humans receive high doses of ionizing radiation

Early effects (deterministic)

Produced by a… of ionizing radiation

Substantial dose

Are effects upon the body that was irradiated

somatic effects

Are effects upon future generations because of irradiation of germ cells in previous generation

Genetic effects

Depending upon the length of time from the moment of irradiation to the first appearance of symptoms of radiation damage, the effects are classified as either

Early or Late effects

Amount of biologic damage a human undergoes as a
result of radiation exposure depends on several factors

1. The amount of ionizing radiation to which the subject is exposed

2. The ability of the ionizing radiation to cause ionization of human tissue

3. The amount of body area exposed

4. The specific body part exposed

The amount of biologic damage for Early effects depends on ?

The actual absorbed dose of ionizing radiation

A point at which symptoms begin to appear and below which they are absent

Threshold

As the radiation dose increases, the severity of these effects also

Increases

What’s the threshold of Hematologic depression

25 rad or 0.25 Gyt

What’s the threshold of Skin erythema?

200 rad or 2Gyt

what’s the threshold of Gonadal Dysfunction?

10 rad or 0.1 mGyt

The threshold for Death by radiation is 200rad/0.25 just as skin erythema how come they differ?

B/c for death to occur the whole body was exposed while skin erythema only the a certain area was exposed

Occurs in humans after whole-body exposure of a large doses of ionizing radiation delivered over a short period of time

Acute Radiation Syndrome

Hematopoietic syndrome (bone marrow syndrome) is a syndrome of ARS which has a threshold of what?

1-10 Gyt

Gastrointestinal syndrome is a syndrome of ARS which has a threshold of how much?

6Gyt-10Gyt

Cerebrovascular syndrome is a syndrome of ARS which has threshold of how much?

50Gyt or more

What is the ARS syndrome that a person can possible survive depending on the amount absorbed of radiation and if blood transfusion is involved?

Hematopoietic syndrome

The average amount of life expectancy after whole body radiation exposure

Mean Survival time

As whole body radiation doses increase, the average time between exposure and death

Decreases (more likely to die)

The mean survival time for mammals after a single whole body dose of radiation is

Dependent on dose (2 – 10Gy)

ARS presents in four major response stages

Prodromal, or initial stage

Latent period

Manifest illness

Recovery or death

The first stage of acute radiation syndrome, which occurs within hours after a whole body absorbed dose of 1 Gy t or more; characterized by nausea, vomiting, diarrhea, fatigue, and leukopenia.

Prodromal, or initial stage

The period of about 1 week after the prodromal stage of acute radiation syndrome, during which no visible symptoms of radiation exposure occur.

Latent period

The stage of ARS when symptoms that affect the hematopoietic, gastrointestinal, and cerebrovascular systems become visible again after a latent period.

Manifest illness

ARS is actually a collection of symptoms associated with

Exposure to high level radiation

Signifies the whole-body dose of radiation that can be lethal to 50% of the exposed population within 30 days

LD 50/30

For adult humans the estimated LD 50/30 dose is

3.0 to 4.0 Gyt. (3.5 Gyt)

A more accurate measure for Humans that signifies the whole-body dose of radiation that can be lethal to 50% of the exposed population within 60 days due to medical intervention

LD 50/60

Repair and recover can occur when cells are exposed to … doses of ionizing radiation

sublethal

Approximately how much of the radiation-induced damage will be irreparable

10%

How much of the remaining irradiated cells will be repaired over time

90%

Cells that are more… are more likely to repair b/c they receive more nutrients

Oxygenated

When cells are exposed to sublethal doses of radiation, repair and recovery may occur because cells

Contain repair enzymes

Organs and tissues sustaining such damage may lose their ability to function, or they may recover If recovery occurs, it may be

Partial or Complete

If organ and tissue recovery fails to occur… of the
irradiated biologic structure results

Necrosis or death

Organ and tissue response to radiation exposure depends on

Radiosensitivity (Wt)

Reproductive characteristics

Growth rate

What are the 3 layers of the skin

Epidermis (outer)

Dermis (middle)

Hypodermis (subcutaneous)

Accessory structures of skin include

Hair Follicles

Sensory receptors

Sebaceous glands

Sweat glands

Epilation or loss of hair (alopecia) is a effect on the skin due to radiation if moderate doses are receive what is the result? and if Large doses are received what is the result?

Moderate→ temporary hair loss

Large→ permanent hair loss

What are some medical procedures that can cause radiation effects on the skin?

Oncology (receiving orthovoltage radiation therapy treatment)

Cardiovascular or therapeutic interventional procedures (high-level fluoroscopy)

Gonadal dose of … depress the male sperm population or
cause a genetic mutation in future

0.1 Gyt

Gonadal dose of …may delay or suppress menstruation in the female

0.1Gyt

Gonadal dose of ionizing radiation that will cause
temporary sterility in the male and in the female

2 Gyt

Gonadal dose of ionizing radiation that will cause
permanent sterility in the male and in the female

5-6 Gyt

HOW MANY MATURE OVA ARE PRODUCED, MATURED AND MADE AVAILABLE FOR FERALIZATION
DURING A WOMAN'S REPRODUCTIVE LIFE

400-500

WHEN ARE HUMAN OVARIES MOST RADIOSENSITIVE?

During the fetal stages of life and during early childhood

Consists of: bone marrow, circulating blood, and lymphoid organs (lymph nodes, spleen, and thymus gland)

Hematopoietic System

Hematopoietic System cells of this system all develop from a single precursor cell, the….

pluripotential stem cell

When lymphocytes, granulocytes, thrombocytes (platelets) and erythrocytes are damaged by radiation exposure, which of the following are possible consequences?

Increased susceptibility to aggressive infectious organisms, high risk of hemorrhage and anemia

What are the 2 major part of the cell

cytoplasm and nucleus

What’s the chemical building material for all living things

Protoplasm

what are the 4 macromolecules

protein

carbs

lipids

nucleic acids