HPS 420 CH 7: LET & RBE & Ch 8: ARS
EXAM STUDY GUIDE
LET (Linear Energy Transfer) - ANSWER The amount of
energy imparted to the medium by a charged particle per unit length of track
(keV/ μ m).
LET equation - ANSWER Δ E/Δ x (change in energy over the change in distance)
Low-LET Radiation - ANSWER Induces radicals more SPARSLEY within a cell
High-LET Radiation - ANSWER Deposits a LARGE amount of energy in a SMALL distance,
causing more DENSE ionizations
RBE (Relative Biological Effectiveness) - ANSWER The ratio of test radiation compared
with Gamma rays or 250 KeV X-rays that PRODUCE SAME BIOLOGICAL EFFECTS
RBE Equation - ANSWER Dose in Gy known Xrays / Dose in Gy from other radiationt
source
Fractionation ____ RBE - ANSWER Increases
, Track Average - ANSWER Divide track into equal lengths, then
calculate the energy deposited in each length, and find the mean
Energy Average - ANSWER Divide the track into equal energy increments and average
the lengths of track over which these energy increments are deposited
RBE gets ____ as dose is REDUCED - ANSWER Larger
As LET _____, RBE _____. - ANSWER Increases, Increases
What is the Reason for Greatest Effectiveness for 100-200 KeV/μ m? - ANSWER At a 100
KeV, it is more likely to produce a DNA DSB from a single particle
The Spacing between ionizations corresponds to the width of the DNA helix
Factors that determine RBE effects - ANSWER 1) Radiation Quality (LET)
2) Radiation Dose
3) # of Dose Fractions
4) Dose Rate
5) Biological System or Endpoint
OER (Oxygen Enhancement Ratio) Equation - ANSWER Dose (hypoxic) / Dose (Aerated)
EXAM STUDY GUIDE
LET (Linear Energy Transfer) - ANSWER The amount of
energy imparted to the medium by a charged particle per unit length of track
(keV/ μ m).
LET equation - ANSWER Δ E/Δ x (change in energy over the change in distance)
Low-LET Radiation - ANSWER Induces radicals more SPARSLEY within a cell
High-LET Radiation - ANSWER Deposits a LARGE amount of energy in a SMALL distance,
causing more DENSE ionizations
RBE (Relative Biological Effectiveness) - ANSWER The ratio of test radiation compared
with Gamma rays or 250 KeV X-rays that PRODUCE SAME BIOLOGICAL EFFECTS
RBE Equation - ANSWER Dose in Gy known Xrays / Dose in Gy from other radiationt
source
Fractionation ____ RBE - ANSWER Increases
, Track Average - ANSWER Divide track into equal lengths, then
calculate the energy deposited in each length, and find the mean
Energy Average - ANSWER Divide the track into equal energy increments and average
the lengths of track over which these energy increments are deposited
RBE gets ____ as dose is REDUCED - ANSWER Larger
As LET _____, RBE _____. - ANSWER Increases, Increases
What is the Reason for Greatest Effectiveness for 100-200 KeV/μ m? - ANSWER At a 100
KeV, it is more likely to produce a DNA DSB from a single particle
The Spacing between ionizations corresponds to the width of the DNA helix
Factors that determine RBE effects - ANSWER 1) Radiation Quality (LET)
2) Radiation Dose
3) # of Dose Fractions
4) Dose Rate
5) Biological System or Endpoint
OER (Oxygen Enhancement Ratio) Equation - ANSWER Dose (hypoxic) / Dose (Aerated)
