MEDRADSC 2X03 - Lecture 5 - Cell Survival Curves

what are the main differences between chromosomal and chromatid aberrations?

chromosome aberrations occur when radiation damage occurs before DNA replication, in which both daughter cells inherit the damaged chromatid whereas chromatid aberrations occur when radiation damage occurs after DNA replication, in which only one daughter cell will be affected at the next division

how can lymphocytes be used to estimate radiation dose?

lymphocytes are sampled and stimulated to divide, chromosomes become visible at metaphase and the rate of aberrations is compared to standards

what are the two types of cell death?

apoptosis and mitotic death

apoptosis

programmed cell death, occurs in an ordered sequence of events

mitotic cell death

cell death that occurs while attempting to divide

what is the most common type of radiation-induced cell death?

mitotic cell death

when is a cell considered to be clonogenic?

it is able to divide successfully

plating efficiency

the fraction of seeded cells that formed colonies

survival fraction

the fraction of cells deemed clonogenic after receiving a dose of radiation

describe the cell survival curve

the survival fractions plotted on a logarithmic scale over the dose on a linear scale

what are the two mathematical models used to approximate cell survival curves?

multi-target model and linear quadratic model

when referring to the multi-target mathematical model, what does the curved initial part of the line of best fit represent?

cell death as a result of a single-event damage

when referring to the multi-target mathematical model (MTM), what does the linear latter portion of the line of best fit represent?

cell death as a result of multi-hit killing

what does unity represent?

100% cell survival

low LET -> __________ present on cell survival curve (MTM)

shoulder

high LET -> no ______ present on cell survival curve (MTM)

shoulder

extrapolation number (n)

the value on the y-axis where the extrapolated line of the linear portion would intersect

the extrapolation number and the quasithreshold dose both are said to represent what aspect of the cell survival curve?

the width of the shoulder

quasithreshold dose (Dq)

the dose at which the extrapolated line of the linear portion would have a survival fraction of unity

D0 slope

the dose at which the surviving fraction is reduced to 37% of unity, for the shoulder of the curve

D1

the dose at which the surviving fraction is reduced from 0.1 to 0.037 of 0.01 to 0.0037, or for the straight line portion of the curve

D1 is always __________ than D0 due to repair capability of cells in low-dose regions of the curve.

larger

what is the multitarget model curve expression?

logen = Dq / D0