Radiation Biology

Question 1

What does a cell survival curve describe?

Answer 1

The relationship between dose and the proportion of cells that survive

Question 2

2 definition of cell death?

Answer 2

Loss of function (differentiated cells) & Loss of reproductive integrity (proliferating cells)

Question 3

What is Cell survival?

Answer 3

A Cell community that kept its reproductive integrity (not only capability)

Question 4

What is Clonogenic capability?

Answer 4

A cell survivor that reproduces indefinitely to produce a large clone or colony.

Question 5

What is the Law of Bergonie & Tribondeau?

Answer 5

The law is that cell radiosensitivity is related to: Cell mitotic rate; Cells that undergo many future mitosis; and Cell that is the most primitive in differentiation.

Question 6

Which cells are the exception to the law of Bergonie & Tribondeau?

Answer 6

Oocytes & Lymphocytes

Question 7

What are the major ‘Direct” effects of radiation on tissue cells?

Answer 7

Hypoplasia & Atrophy (inhibition of mitosis, precocious maturation, mitotic linked death)

Question 8

Salivary glands are affected how, and by what radiation dose?

Answer 8

At 20-30 Gy they recover in 6-12 months with reduced salivary flow.
At 60 Gy we see complete destruction of the gland,

Question 9

What is the definition of ‘Doubling dose’?

Answer 9

The amount of radiation a population requires to produce, in the next generation, as many additional mutations as arise spontaneously.

Question 10

What is the Nyquist Theory?

Answer 10

The best resolution is half (0.5) the sampling frequency.

Question 11

3 types of radiation damage?

Answer 11

Lethal, Potentially lethal damage (PLD), and Sublethal damage.

Question 12

What are the 4 R’s of radiobiology?

Answer 12

Repair, Reassortment, Repopulation, Reoxygenation

Repair, Reoxygenation, Redistribution, Repopulation

Question 13

What are 5 most radiosensitive tissues?

Answer 13

Lymphoid, Hematopoietic, Spermatogenic, Ovarian follicular epithelium, intestinal epithelium.

Question 14

What are 4 medium radiosensitive tissues?

Answer 14

Connective tissue, Fine vasculature, Growing cartilage & bone, Conn. tissue of the CNS.

Question 15

What are 5 radioresistant tissues?

Answer 15

Mature cartilage & bone, Epithelium of many tissues, neuronal tissue, muscle (striated)

Question 16

What are the 4 stages of Acute radiation syndrome?

Answer 16

Prodromal, Latent, Manifest illness, Recovery or death.

Question 17

What are the signs of Prodromal (NVD) stage?

Answer 17

Nausea, vomiting, diarrhea. (Deterministic effect)

Question 18

What is the Latent stage?

Answer 18

When the patient looks and feels generally healthy.

Question 19

What is the Manifest illness stage?

Answer 19

When the patient has symptoms, and can last from hours to months.

Question 20

What is Cerebrovascular syndrome? At what dose?’Early Lethal Effects’?

Answer 20

Happens at >50 Gy. Severe NVD, disorientation, respiratory distress, and death occurs within hours

Question 21

What are signs and dose for Gastrointestinal syndrome?

Answer 21

> 10 Gy. Death within 3-10 days. Symptoms due to depopulation of epithelial lining of GI tract. Severe NVD.

Question 22

What are signs and dose of Hematopoietic syndrome?

Answer 22

<8Gy. Death within 30-60 days post radiation. Suppresses normal bone marrow and spleen functions.

Question 23

Compare the pathophysiology of GI syndrome & hematopoietic syndrome.

Answer 23

The difference is the turnover time of the cells in the respective tissues. GI cells turnover much faster, so this syndrome will kill you faster .

Question 24

In Humans what is LD 50/30 and LD50/60 doses?

Answer 24

LD 50/30 is defined as the dose which causes a mortality rate of 50% of a group within a specified time.
LD 50/30 occurs at ~6 Gy.
LD 50/60 occurs at ~ 4 Gy.

Question 25

What is the major tumor suppressor gene?

Answer 25

P53

Question 26

What is 'Adaptive Response'?

Answer 26

This is when large radiation exposure is preceded by by a small "tickle" dose, the effect of the large dose can be diminished. (like getting a tan to prevent sunburn)

Question 27

What are the most Radioresistant phases of the cell cycle?

Answer 27

S & G2.

Question 28

What are the most Radiosensitive phases of the cell cycle?

Answer 28

M (and late G2???)

Question 29

What are the advantages to preoperative XRT?

Answer 29

Unresectable lesions may become resectable; Extent of surgical resection diminished; smaller treatment portals; decreased metastasis. Disadvantage is decreased wound healing.

Question 30

What are advanatages of post-operative XRT?

Answer 30

Better surgical staging; greater dose can be given; tissue heals better; surgical resection is easier. Disadvantage is distant metastasis by manipulation.

Question 31

What is the acute toxicity limiting factor for an aggressive XRT schedule?

Answer 31

Mucositis

Question 32

What is the dose required for permanent sterility in men and women?

Answer 32

Men - 6 Gy single dose | Women - 2 Gy single dose

Question 33

What is the monthly radiation limit for pregnant women?

Answer 33

0.5 mSv per month

Question 34

What is the difference between natural cataracts & radiation induced cataracts?

Answer 34

Natural cataracts start on the external aspect of the lens, while radiation induced cataracts start on the internal aspect (at the posterior pole).

Question 35

What is the threshold dose for cataracts?

Answer 35

2 Gy, or 8 Gy if fractionated. (also the latent period becomes shorter if dose is increased)(This shows its a deterministic "late" effect).

Question 36

What is 'Inverse dose Rate'?

Answer 36

This is when decreasing the dose rate actually increases cell killing. Due to allowing cells to cycle through the cell cycle, instead of stopping at G2.

Question 37

Definition of Absorbed Dose.

Answer 37

Measure of energy absorbed by any type of radiation per unit mass of any type of matter. Unit - Gy.

Question 38

Definition of Equivalent Dose.

Answer 38

Used to compare biologic effects of different types of radiation. Uses Radiation factor. Unit - Seivert.

Question 39

What is formula for Equivalent dose?

Answer 39

HT = ∑ WR x DT

Question 40

Definition of Effective Dose?

Answer 40

The sum of all of the weighted equivalent doses in all the tissues or organs. Uses a Tissue weighting factor.

Question 41

What is the 'Negligible Individual dose'?

Answer 41

Dose below which further efforts to reduce radiation exposure to the person are unwarranted. 0.01 mSv.

Question 42

What are the dose limits for Occupational exposure?

Answer 42

50 mSv/year, or 10 mSv x Age.

Question 43

What is the effective dose limit for a pregnant woman?

Answer 43

0.5 mSv/month

Question 44

What is effective dose limit for the public?

Answer 44

Frequent exposures - 1 mSv/year. Infrequent exposures - 5 mSv/year.

Question 45

What is Dose limit for Deterministic effects for the Lens of the Eye?

Answer 45

150 mSv/year.

Question 46

What is the does limit for deterministic effects for the skin, hands, and feet?

Answer 46

500 mSv/year.