Radiosensitivity And Cell Effects PPT Flashcards
What factors affect radio sensitivity?
Cell type
LET of radiation
RBE— comparison of damage
Fractionation and protraction
What is a radiosensitizer?
A radiosensitizer is a drug that makes tumor cells more sensitive to radiation therapy.
What is the effect of oxygen in relation to radiosensitizers?
Oxygen combined with low LET radiation enhances the effect of radiosensitizers.
What is a radioprotector?
Radioprotectors are compounds designed to reduce the damage in normal tissues caused by radiation.
What is an example of a radioprotector?
Amifostine (WR-2721) is an example of a radioprotector.
What does the Law of Bergonie and Triboneau state about radiosensitivity?
Radiosensitivity is a function of the metabolic state of the tissue being irradiated.
What types of cells are more affected by radiation according to the Law of Bergonie and Triboneau?
Radiation is more effective against actively dividing cells, undifferentiated cells, and cells with a long dividing future.
What does the Modified B& T Theory by Ancel and Vitemberger state?
The inherent susceptibility of any cell to damage by ionizing radiation is the same, but the time of appearance of radiation-induced damage differs among different types of cells.
What are the two types of tissues in relation to radiation response according to Ancel and Vitemberger?
Late Responding Tissue and Early Responding Tissue.
What does LET stand for?
LET stands for Linear Energy Transfer.
What is RBE?
RBE stands for Relative Biologic Effectiveness.
What is OER?
OER stands for Oxygen Enhancement Ratio.
How does LET affect biological effects?
As LET increases, the ability of the radiation to cause biologic effects also generally increases.
What does RBE measure?
RBE measures the capabilities of radiation with differing LETs to produce a particular biologic reaction.
What is the Oxygen Enhancement Ratio?
OER is the ratio of the radiation dose required to cause a particular biologic response in oxygen-deprived conditions to the dose required under normal oxygenated conditions.
What is the formula for RBE?
RBE = Dose of reference radiation (Gy) / Dose of test radiation (Gy)
What is the reference radiation of kVp x rays in the RBE formula?
250-kVp x-rays
What is the RBE of the test radiation if it takes 10 Gy of 250-kVp x-rays to produce the same reaction as 2 Gy of test radiation?
5
RBE = 10 Gy / 2 Gy = 5
I’m general, X rays and gamma rays have an ORT of about ____ when radiation dose is high.
3
What is the formula for OER?
Radiation dose WITHOUT oxygen/ dose required WITH oxygen
What is the ideal situation for the dose response curve?
The ideal situation is when the dose response curve for damage in critical normal tissues sits well to the right of that for normal control.
What does TR represent?
TR represents the Therapeutic Ratio, calculated as TR = Normal Tissue Tolerance Dose (NTTD) / Tumor Lethal Dose (TLD).
What are the categories of cell populations based on radiosensitivity?
- Vegetative intermitotic (VIM) cells
- Differentiating intermitotic (DIM) cells
- Multipotential connective tissue (MPCT) cells
- Reverting postmitotic (RPM) cells
- Fixed postmitotic (FPM) cells
Which cells are most sensitive to radiation damage?
Actively dividing cells are most sensitive to radiation damage.
