Principles Of Radbio Flashcards
the response of irradiated tissue is primarily determined by
The amount of energy deposited per unit of mass;
Dose
Linear Energy Transfer
rate of energy transferred from ionizing radiation to soft tissue.
Unit is keV / um
The LET/ Linear Energy Transfer of diagnostic x-ray is about
3 keV/um
3 kiloelectron volt of energy transferred per micrometer of track length in soft tissue
The ability of ionizing radiation to produce a biologic response increases as
LET of radiation increases
When LET is high, ionizations occur frequently,
Increasing the probability of interaction with the target molecule
As LET of radiation increases, the ability to produce biologic damage also increases. This effect is quantitatively described by
The relative biologic effectiveness (RBE)
Define dose response relationships
A mathematical and or graphical function that relates radiation dose to observed effects.
What is an implication for diagnostic imaging
Fetus and children are far more radiosensitive compared to an adult
Standard radiation =
200 to 250 kVp radiation
Diagnostic x-rays have an RBE, relative biological effectiveness =
1
Radiation with lower LET than diagnostic x-rays have an RBE of
Less than 1
Radiation with higher LET than diagnostic x-rays, have RBE
Over 1
If the time of irradiation is longer, —– is required to produce the same effect.
Higher dose
Dose protraction
When dose is delivered at a lower dose rate, continuously
Dose fractionation
Dose is delivered in spurts.
