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Flashcards in Radiobiology Deck (204)
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1

Which of the DNA bases are single-ring (pyrimidine) and which are double-ring (purine)?

Pyrimidine = thymine & cytosine
Purine = adenine & guanine

2

What is the D0 dose?

The dose of radiation that induces an average of one lethal event per cell, leaving 37% still viable

3

Why is DNA in cells more resistant to radiation damage than free DNA?

-presence of molecular scavengers
- physical protection via protein (histone) packaging

4

What do nuclear foci of phosphorylated 53BP1 indicate?

DNA DSB

5

What is the extrapolation number, n? What type of curve results if n is large?

n is a measure of shoulder width
if n is large, the survival curve has a broad shoulder

6

Which genes appear to be responsible for induction of senescence?

Rb, p53

7

Following radiation, one cell line shows clear DNA laddering on electrophoresis, while another shows little evidence of DNA laddering. Which of these is more likely radiosensitive?

cell line with laddering --> indicates apoptosis

this is likely the more radiosensitive cell line

8

What is the OER for protons?

2.5-3.0

equivalent to x-rays

9

What is the average LET during the entrance plateau for protons? during the Bragg peak?

entrance: 0.5keV/um
Bragg peak: 100keV/um

10

The probability of which type of effect increases with radiation dose: deterministic or stochastic?

Both

11

What type of effect has a practical threshold dose and increases in severity with dose: deterministic or stochastic?

Deterministic

12

Which type of effect is best described as "random", with no threshold observed and no change in severity with dose: What type of effect has a practical threshold dose and increases in severity with dose: deterministic or stochastic?

Stochastic

13

Which radiation-induced malignancy has the shortest latent period?

Leukemia
Peak incidence at 5-7 years

14

T/F: Radiation-induced solid tumors occur in younger patients than spontaneous tumors.

FALSE
Radiation-induced solid tumors tend to be expressed later in life, at the same time as spontaneous tumors of the same type

15

Which of the following risk models for malignancy following radiation exposure is favored by the BEIR committee:
absolute risk model
relative risk model
time-dependent risk model

Time-dependent risk model

16

Name the two international committees on radiation protection.

UNSCEAR - United Nations Scientific Committee on the Effects of Atomic Radiation (scholarly)
ICRP - Int'l Council on Radiological Protection

17

Name the two US committees on radiation protection.

BEIR - Biological Effects of Ionizing Radiation (US Nat'l Academy of Sciences)
NCRP - Nat'l Council on Radiological Protection and measurement
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18

T/F: The incidence of CLL increases following radiation.

False - AML/CML account for most of the increase

19

The incidence of which types of leukemia increases most after radiation of a human population?

AML and CML

20

Which populations are most susceptible to increased incidence of ALL and stem cell leukemia following radiation?

Children

21

Which type of cancer has the highest relative risk of any malignancy following radiation of a population?

Leukemia (specifically AML, CML)

22

The risk of leukemia rises in a dose-dependent manner up to what dose?

3 Sv
Risk per unit dose at 1 Sv is about 3X greater than 0.1 Sv

23

Which population is most sensitive to induction of thyroid carcinoma following radiation?

Children

24

What is the threshold dose to the developing fetus for radiation-induced mental retardation?

0.3Gy

25

What is the unit for absorbed dose (J/kg)?

Gy

1 Gy = 100 rad

26

What dose rate defines high dose rate brachytherapy?

HDR is >12Gy/h

27

What dose rate defines low dose rate brachytherapy?

LDR brachytherapy is ~2Gy/hr

28

At what timeframe following RT to the globe is retinal hemorrhage and degeneration expected?

3-6 months

These lesions progress over time

29

How much energy is dissipated per ionization event in ionizing radiation?

33eV

30

What is the velocity (c) of electromagnetic radiation?

3x10^10 cm/s (3x10^8 m/s)