Exam 1 Review Radiation Biology & Protection

What is one half of the chromosome called?

Chromatid

What are the three types of acute radiation syndromes?

Hematopoietic, Gastrointestinal and Cerebrovascular

What are the four stages of acute radiation syndrome?

Prodromal or initial, Latent, Manifest Illness, Recovery or Death

Which stage has no visible symptoms?

Latent

What is the absolute minimum dose for acute radiation syndrome?

1-2 Gray (100-200 RAD)

The three syndromes are based on the dose received. What is the minimum dose for the three syndromes?

Hematopoietic = 1-10 Gray, GI = 6-10 Gray, Cerebrovascular = greater than 50 Gray

Of RBC, WBC, and platelets, which live the longest? Shortest?

WBC = 1-2 days, Platelets = 7-10 days, RBC = 120 days

What complications would occur with hematopoietic syndrome?

Infection, hemorrhaging, drop in blood counts

What complications would occur with GI syndrome?

Diarrhea, dehydration, anorexia, electrolyte imbalance

Does the rate in which someone receives a dose of radiation matter?

Yes. This is the basis for radiation therapy. How? It gives healthy cells time to repair, while the unhealthy (cancerous cells, which replicate faster) are more damaged.

What is on the X and Y axes of dose-response curves?

X = dose and Y = effect or response

What is the difference between linear no-threshold and linear threshold?

No threshold implies that risk increases as the dose increases. Threshold implies there is a minimum dose that must be received before risk goes up

Describe the dose-response curve used for stochastic effects.

linear no-threshold

Describe the dose-response curve for non-stochastic effects.

linear threshold (may or may not be linear). Low dose = linear; high dose = non-linear (cataract formation)

What is the smallest unit into which a chemical element can be broken down without losing its chemical identity?

Atom

What are the particles in a nucleus called? Nucleons (protons and neutrons) of protons, neutrons, and electrons.

What is the smallest: electrons. What is the largest: neutrons

What type of decay occurs:

Too many neutrons: beta negative. Too many protons (too few neutrons): beta positive or electron capture

How is bremsstrahlung radiation produced?

Electrons passing by the nucleus, slowing down and excess energy given off as x-ray

Write these down and put them in order from smallest to largest: atoms, organs, tissues, molecules, cells, and organisms.

Atoms, molecules, cells, tissues, organs, organisms

What is the definition of attenuation?

Absorption, plus scattering

How do absorption and scatter differ?

There is energy left over in a scatter reaction.

Describe the photoelectric effect.

A photon comes in and knocks out an inner shell electron. All of the energy from the photon is used to knock out the electron. Any leftover energy is transferred to the photoelectron.

Describe Compton scatter.

A photon comes in and knocks out an outer shell electron. Some of the energy is transferred to the electron. The rest of the energy is scattered (changes direction).

Give examples of types of ionizing radiation.

x-ray, gamma rays, alpha, beta

Give examples of non-ionizing radiation.

ultraviolet, visible light, microwave, radiowaves, infrared

What is the difference between ionizing and non-ionizing radiation?

Energy— ionizing has enough energy to create ions by removing an electron.

What does LET stand for?

linear energy transfer

What are the units of LET?

keV/um

What is considered low LET?

X-rays, gamma rays and beta particles

What does RBE stand for?

Relative Biologic Effect

What are the units of RBE?

there are none; it is a ratio

What is the numerator of RBE?

Reference radiation (dose delivered by 250 kVp x-rays)

What is in the denominator of RBE?

Test radiation (dose delivered to produce the same biological effect)

When comparing high RBE to low RBE, what does this number mean?

The test radiation is in the denominator, so the smaller the number, the higher the RBE. The higher the RBE, the more effective the test radiation is compared to the reference radiation.

What does OER stand for?

Oxygen Enhancement Ratio

What are the units of OER?

There are none; it is a ratio

What is in the numerator for OER?

Dose in Hypoxic (without oxygen)

What is in the denominator for OER?

Dose in Aerobic (with oxygen)

When comparing a high OER to a low OER, what does this number mean?

The denominator is with oxygen. The lower that number, the higher the OER. A higher OER means that adding oxygen will make the cell more sensitive.

Why will OER never be less than 1?

The numerator is without oxygen. The denominator is with oxygen. It will always take less dose with oxygen (denominator). This means the numerator will always be greater than the denominator, so the answer will be greater than one.

When comparing high LET and low LET, which one will have the highest OER?

Low LET

Why does low LET have the highest OER?

Low LET damage will be due to radiolysis of water. Oxygen is part of water. The more water, the greater the cell will become more sensitive (higher OER) in the presence of low LET radiation • High LET radiation damage is mainly due to direct hits, so water does not come into play as much (lower OER)

1. LET definition: A high energy proton beam is used in radiation therapy to treat a tumor. The total energy being deposited is 100 MeV (100,000 keV). The energy is being deposited over a distance of 2 cm (20,000 um). What is the LET (in keV/um)?

a. 100,000 keV/20,000 um b. LET = 5 keV/um

2. LET application: An alpha particle with an energy of 4 MeV travels through a tissue, depositing energy at a rate of 120 keV/μm. How far will the alpha particle travel before it has deposited all its energy?

a. 4 MeV (1,000 keV/1 MeV) = 4,000 keV b. 4,000 keV(um/120 keV) = 33.33 um

3. RBE definition: A certain type of radiation therapy uses X-rays with an RBE of 1.0 and a dose of 2 Gy. A new type of proton therapy being considered, but will require a dose of 1.33 to produce the same results. What is the RBE of the new proton therapy?

a. RBE = reference radiation/test radiation b. RBE = 2 Gy/1.33 Gy c. RBE = 1.5

4. RBE application: A patient receives a 1.2 Gy dose of alpha particles with an RBE of 20. Calculate the equivalent dose in terms of X-rays

a. RBE = reference radiation/test radiation b. 20 = x/1.2 c. RBE = 24

5. OER definition: A dose of 6 Gy is required to achieve a certain biologic damage in hypoxic tissue. In oxygenated tissue, the dose is 2.4 Gy. What is the OER?

a. OER = hypoxic/ oxygenated tissue b. OER = 6/2.4 = 2.5

6. OER application: A particular type of radiation therapy has an OER of 2.5. If the dose required in hypoxic state is 10 Gy, what is the dose in an oxygenated state?

a. OER = hypoxic/oxygentated b. 2.5 = 10/x c. 4

How do you describe ionizations in air?

Exposure

Units of Exposure?

Roentgen or C/kg

What is the difference between exposure and exposure rate?

Exposure is in units of Roentgen and describes the total amount. Exposure rate is in units of R/hr or mR/hr and describes the amount of radiation exposure per unit time.

What is absorbed dose? Also, what are the units?

RAD or Gray

How do you convert RAD to Gray?

100 RAD = 1 Gray

What is equivalent dose?

Takes into account the type of radiation and its biological effects.

What are the units of equivalent dose?

REM or Sv

How do you convert REM to Sv?

100 REM = Sv

What is effective dose?

Takes into account the sensitivity of different tissues

What are the units of effective dose?

REM EDE or SV EDE

How do you go from absorbed dose to equivalent dose?

Absorbed dose multiplied by radiation weighting factor

How do you go from equivalent dose to effective dose?

Equivalent dose multiplied by the tissue weighting factor

Which types of radiation have a radiation weighting factor of 1?

X-rays, gamma rays, electrons and positrons

What is the tissue weighting factor for the whole body?

one / 1

Define Stochastic (probabilistic)

probability of the effect increases with increasing dose (severity does not)

Give Examples of Stochastic (Probabilistic)

cancer and genetic effects

Non-stochastic (deterministic)

Severity of the effect increases with dose

Give Examples of Non-stochastic (deterministic)

erythema and epilation, acute radiation syndrome, cataracts

Name some early effects of radiation

Erythema, epilation, hematopoietic syndrome, gastrointestinal syndrome, cerebrovascular syndrome

Name some late effects of radiation

Cataract formation, fibrosis, organ atrophy, loss of parenchymal cells, reduce fertility, sterility, cancer and genetic mutations

Name Non-stochastic (deterministic) effects

Skin reddening (erythema), skin damage, hair loss, reduced fertility, sterility, cataracts, and lethality. (all except cancer and genetic mutations)

Name stochastic (probabilistic) effects

cancer and genetic mutations

What are the somatic cells?

all except the genetic ones, germ cells

Which is the most sensitive to radiation?

Bone marrow or muscles: bone marrow Ovaries or nerves: ovaries, Small intestine or lymph nodes: lymph nodes Bone or testis: testis

What is the semi-permeable barrier controlling the entry and exit of substances in the cell?

Cell Membrane

What in the cell contains the DNA?

Nucleus

What is the powerhouse of the cell and responsible for energy production?

Mitochondria

The cytoplasm is the space between the nucleus and the cellular membranes. In the cytoplasm, you have organelles and intracellular fluid. What is the intracellular fluid called?

Cytosol

How many daughter cells are created with mitosis?

2

Which cells undergo mitosis?

Somatic cells

How many daughter cells are created with meiosis?

4

Which cells undergo meiosis?

Germ cells

Put the following in the correct order starting with prophase: Anaphase, Telophase, Metaphase, Interphase

Prophase, Metaphase, Anaphase, Telophase, Interphase

What is the longest phase?

Interphase

When is the cell the most radioresistant?

Interphase

When is the cell most sensitive?

Mitosis

When comparing Meiosis and Mitosis, which phase is missing in Meiosis?

Interphase (which is the most radioresistant)

What is one half of the chromosome called?

Chromatid

What is at the center of the chromosome called?

Centromere

What are the arms of the chromosome called?

Short arm and long arms

How is DNA and RNA different?

RNA is single-stranded, and Uracil replaces thymine

Compare a single strand vs a double strand break. Which is reversible, which is caused by low LET?

Single strand break is caused by low LET and is reversible. A double strand break can be caused by low or high LET, but more likely by high LET. In a double strand break, if it occurs at the same base pair level, repair is unlikely. In double strand, if damage in two places is close together, repair will be unlikely

What is a mutation of DNA?

Change or loss of nitrogenous base, incorrect information passed on. (Correct pairing: A-T and G-C)

What is the difference between direct action and indirect action of radiation with matter?

Direct is radiation ionizing molecules of DNA, indirect is radiation ionizes water molecules and creates free radicals that damage DNA

Radiolysis of water results in four substances that are the primary sources of indirect biological damage. What are they?

Hydroxyl free radical, Hydrogen free radical, Hydroperoxyl free radical, Hydrogen peroxide

What is the term for programmed cell death for eliminating damaged cells?

Apoptosis

We are made up of 80-85% water, what is the second most component of what we are made up of?

Protein = 15%

How would you define radiation biology?

The study of the sequence of events that follows the absorption of energy from ionizing radiation, how the organism compensates for this energy and the damage produced

Explain the Law of Bergonie and Tribondeau in terms of cell division rate and degree of differentiation.

directly proportional to cell division rate and indirectly proportional to degree of differentiation (the more differentiated, the less sensitive)

What does restitution mean in chromosome damage?

Chromosome is repaired back to its original state. This is with Low LET radiation

Where does MOST of our data come from for radiation biology?

A-bomb survivors

What is on the x and y axes of a cell survival curve?

X = dose Y = survival fraction