Cell survival and Radiosensitivity

Question 1

Cell death

Answer 1

loss of function of cells that do not proliferate otherwise or reproductive death for proliferating cells

Question 2

clonogenic cell

Answer 2

able to proliferate indefinitely and form a large colony from a single cell

Question 3

the formula for plating efficiency

Answer 3

colonies observed/number of cells plated

Question 4

surviving fraction

Answer 4

colonies counted/cells seeded*PE

Question 5

D0 dose

Answer 5

a dose that introduces an avg dose for one lethal event per cell leaves 37% still viable

Question 6

ED50

Answer 6

The dose that reduces cell survival to 50%, if repeated reduce survival to 25% and etch

Question 7

Cell killing follows the exponential relationship

Answer 7

True and SF never reaches 0.

Question 8

Effect = 𝛼D

Answer 8

D/D0, D0 = 1/𝛼. Slope 1/D0

Question 9

SF formula

Answer 9

SF= exp (-D/D0)= exp (-𝛼D). When D = D0,
SF = exp (-1) = 0.37

Question 10

Linear-Quadratic Model

Answer 10

Dual radiation action
First component – cell killing is proportional to dose
Second component – cell killing is proportional to (dose)2

Question 11

Multi-Target Model

Answer 11

Based on the probability of hitting the “target”

Question 12

2 Component Model formula

Answer 12

S = S1 (single event killing)*S2 (two-event killing)= exp(−(αD+βD^2))

Question 13

Multi Target Model Assumptions:

Answer 13

the cell contains n targets;
each target inactivated by one hit;
inactivation of one target is a sublethal event;
to kill the cell all targets must be hit;
on average there are one hit per target for a dose D0, S=exp(-D/D0)

Question 14

Significance of the Shoulder

Answer 14

with low LET radiation cell can withstand higher doses if given after some time after conditioning dose. At hight LET no effect of the shoulder.

Question 15

DNA as a target cell killing

Answer 15

Cells are killed by radioactive tritiated thymidine incorporated into the DNA. The radiation dose results from short-range alpha particles and is therefore very
localized.

Question 16

Apoptotic Death

Answer 16

programmed cell death, characterized by a stereotyped sequence of morphologic events. Dying cell rounds up and detaches from its neighbors.
Chromatin condensation, nucleus fragmentation àcell shrinkage
Cross-linking of proteins and loss of water

Question 17

Mitotic Death (necrosis

Answer 17

Cells die attempting to divide because of damaged chromosomes

Question 18

Autophagic Cell Death

Answer 18

Self-digestive process that uses lysosomal degradation or long-lived proteins and
organelles to restore or maintain cellular homeostasis

Question 19

Senescence

Answer 19

Programmed cellular stress response – unique response to accumulation of
damage to a cell

Question 20

cell survival curve

Answer 20

the relationship between the fraction of
cells retaining their reproductive integrity and the absorbed
dose

Question 21

High LET radiation

Answer 21

alpha particles and low-energy neutrons