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Radiation Biology > from_flashcardlet_20150722213917 > Flashcards

from_flashcardlet_20150722213917

1
Q

Distinguish between the direct and indirect biological effects of ionizing radiation

A

Direct effects are the result of radical formation by the direct energy transfer from ionizing radiation to a biological molecule. Direct effects make up one third of the biologic effects as a result of radiation. Indirect effects produce radicals of biologic molecules through the radicals produced by the interaction of the radiation with water molecules.

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2
Q

deterministic effects of ionizing radiation

A

Caused by killing of many cells, a Threshold exists, all show effect above threshold

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3
Q

Stochastic effects of ionizing radiation

A

sublethal damage to DNA, no threshold, no relationship between severity and dose, Greater dose = greater chance of effect

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4
Q

whole body radiation syndromes

A

PLHGCC (Paul Loves His Girls Completely Caring)Predromal period, Latent period, Hematopoietic syndrome, Gastrointestinal syndrome, Cardiovascular and CNS Syndrome

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5
Q
  1. Explain radiosensitivity at the level of the cell cycle, and at the level of various cell types and organs
A

Cells are most susceptible during the M and G1 phases of mitosis. Rapidly proliferating cells are most sensitive to radiation damage so organs containing a higher proportion of rapidly dividing cell or more primitive cells are more sensitive to damage.

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6
Q

Sources of background radiation

A

cosmic and terrestrial. Terrestrial is broken down further into internal and external.

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7
Q

Single largest source of background

A

Radon, considered to be internal and it is its decay products that are damaging, not Radon itself

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8
Q

Main sources of terrestrial external radiation

A

potassium 40 and decay products of uranium 238 and thorium 232 in the top 20 cm of soil

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9
Q

components of cosmic radiation

A

subatomic particles and photons from sun, and their interactions with earth’s atmosphere, 0.4mSv global avg

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10
Q

radiation dose limits for occupational

A

stochastic 50 mSV; Deterministic 150 mSv to lens of eye or 500 mSv to skin and extremeties

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11
Q

radiation dose limits for public

A

stochastic 5 mSv; 50 mSv to lens of eye, skin, or extremeties

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12
Q

give two most widely recognized advisory bodies

A

NCRP and ICRP

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13
Q

regulatory agency that actually enforces laws

A

NRC

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14
Q

In what areas is the NRC involved

A

regulates special nuclear material, source material, and by-product material used in commercial nuclear power, research, medicine, and other commercial activities

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15
Q

Who regulates the manufacture of x-ray sources and radiopharmaceuticals

A

FDA

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16
Q

Predromal period of radiation syndrome

A

minutes to hours after a 1.5Gy exposure, anorexia, nausea, vomiting, diarrhea, fatigue, weakness. The higher the dose the more rapid the onset.

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17
Q

Latent period of radiation syndrome

A

dose dependent as far as length of time, hours, days or weeks in which there are no signs or symptoms

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18
Q

Hematopoietic syndrome

A

dose 2-7 Gy, damage to blood precursor cells result in bleeding, infection, and anemia

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19
Q

Gastrointestinal syndrome:

A

7-15 Gy, damage to basal cells of intestinal lining which causes lack of nutritional absorption, bleeding into intestines

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20
Q

Cardiovascular and CNS Syndrome:

A

Cardiovascular and CNS Syndrome: excess of 50 Gy causes death in 1-2 days, stupor, incoordination, disorientation, and convulsions, mechanism unknown but suggestive of neuronal damage and vasculature of brain

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21
Q

Three main types of personal dosimetry devices

A

TLDs, pocket dosimeters, and film badges

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22
Q

high kVp produces a high or low contrast image

A

produces a low contast image. That is to say, it produces a long grayscale compared to a 40 kVp image if mA is also adjusted

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23
Q

magnification formula

A

(a + b) / a, where a is the distance from source to object and b is the distance from object to detector

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24
Q

Variables for Shielding Calculations

A

P = shielding design goal (mGy/wk)Controlled spaceUncontrolled spaceT = occupancy factor (proportion of time space is occupied, for uncontrolled space)W = workload (mA-min/wk)U = use factor (proportion of time beam aimed at primary barrier)DistancekVp

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25
Q

What happens to chromosomes if they are irradiated early in interphase before replication (G1 or early S)

A

Chromosome aberrations

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26
Q

What happens to chromosomes if they are irradiated late in interphase after replication (G2 or late S)

A

Chromatid aberrations

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27
Q

Lethal forms of Aberration repair

A

I dicentric formation and ring formation

28
Q

Calculate planting efficiency (PE)

A

Amount counted after incubation period. Divided by amount that were seeded times 100

29
Q

Calculate surviving fraction

A

See photo

30
Q

Survival curves for sparsely ionizing radiation i.e. x-rays

A

Has a shoulder at low doses and turns linear at higher doses

31
Q

Survival curves for densely ionizing radiation i.e. neutrons or alpha Rays

A

No shoulder strictly linear

32
Q

Define apoptosis and list some of the steps

A

Programmed cell deathCan be induced by radiationSo sees its communication with its environmentSell rounds up and detaches, condensation of the chromatin, fragmentation of the nucleusCell separates into fragments (apoptotic bodies)DBS occur

33
Q

Mitotic death

A

Induced by radiation, cell dies while attempting to divide, death may occur early or late in the division following a radiation. If so can undergo five mitosis then it is surviving

34
Q

Multifraction

A

Equal doses separated by sufficient time to allow for sub-lethal damage repair

35
Q

Oxygen enhancement ratio (OER)

A

Ratio of hypoxic to aerated doses needed for same biological endpoint

36
Q

Chronic hypoxia

A

Limited diffusion distance of O2 through respiring tissues, tumors may outgrow blood supply leaving 02 starved regions

37
Q

Acute hypoxia

A

Blood vessels can be temporarily shut down and rapidly reopen to supply to tissues with O2

38
Q

Estimated to diffusion distance of oxygen in respiring tissue

A

70 microns

39
Q

Absorbed dose

A

a measure of the energy absorbed per unit mass of tissue

40
Q

D250/Dr

A

the doses of x-rays and the test radiation required for equal biological effect

41
Q

Factors that Determine the RBE

A

LETRadiation doseNumber of dose fractionsDose rateBiologic system or end point

42
Q

Equivalent Dose (HT)

A

The quantity produced by multiplying the Absorbed Dose (D) by the weighting factor(When absorbed dose is expressed in gray, the equivalent dose is in sievert (Sv) if absorbed dose is in rad, the equivalent dose is in rad equivalent man (rem))

43
Q

CKI- p16 (CDK inhibitor p16)

A

This protein inhibits the CDK4/6 and ensures that it can no longer interact with cyclin D1 to cause the cell cycle progression.

44
Q

Effect of X-ray on Synchronously Dividing Cell Cultures

A

Cells are MOST sensitive at or close to mitosis.Resistance is usually greatest in the latter part of S phase.

45
Q

Double DNA in S phase…why more resistant?

A

Level of sulfhydryl (SH) compounds in cell increase during SSH are powerful radio-protectors

46
Q

DNA double-strand breaks in the G1 phase of the cell cycle

A

repaired by non-homologous recombination

47
Q

DNA double-strand breaks in the S/G2 phase of the cell cycle

A

repaired by homologous recombination

48
Q

Define RBE

A

The RBE of some test radiation (r) comparedwith x-rays is defined by the ratio Dzso/Dr, whereDzso and D. are, respectively, the doses of x-raysand the test radiation required for equal biologicaleffect.

49
Q

define free radical

A

A fragment of an atom or moleculethat contains an unpaired electron whichtherefore make it very reactive.

50
Q

equivalent dose

A

It is defined as the product of the averageabsorbed dose in a specified organ or tissue andthe radiation weighting factor values.

51
Q

effective dose

A

It is defined as the sum over specifiedtissues of the products of the equivalent dosein a tissue and the weighting factor for thattissue.

52
Q

Most radiation sensitive to least cell cycle stages

A

M-G2-G1-S

53
Q

Law of Bergonié and Tribondeau

A

Cell radiosenstivity is related to:Cell mitotic rateCell that undergo many future mitosisCell that is most primitive in differentiationOocytes and Lymphocytes are exception

54
Q

cataract dose threshold

A

2 – 5 Gy

55
Q

Weeks range for mental retardation when exposed in-utero

A

8 to 15 weeks of gestation

56
Q

Doubling Dose

A

Amount of radiation the a population requires to produce, in the next generation, as many additional mutation as arise spontaneously

57
Q

The Four stages of ARS

A

Prodromal stage (N-V-D stage)Latent stageManifest illness stageRecovery or death

58
Q

As the dose decreases, the RBE of a given radiation type

A

increases

59
Q

The RBE varies with increasing LET as follows

A

it increases with LET values up to 100 keV/micrometer and subsequently decreases with increasing LET.

60
Q

The relation between OER and LET is as follows

A

OER has a value of about 3 at low LET values and then decreases to unity at high LET values (approximately 200 keV/micrometer).

61
Q

three lethal aberrations

A

dicentric and the ring, which arechromosome aberrations, and the anaphase bridge, which is a chromatid aberration.

62
Q

Which photon processes are dominant in the context of diagnostic radiology?

A

Compton scattering and photoelectric effect.

63
Q

Toxins produced by ionizing radiation

A

HO2 - hydroperoxyl free radical H2O2- hydrogen peroxide

64
Q

The cell exceptions to the law of bergonie and tribondeau

A

Lymphocytes and oocytes

65
Q

Period of maximum sensitivity of the brain post conception

A

8 to 15 weeks

66
Q

pie chart of annual effective dose

A

see picture

Radiation Biology (1 decks)

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