Radiation Biology

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Know the difference between Fractionation and Protraction,and the benefits of them.
- Fractionation-A dose delivered in smaller equal doses
- Protractionation-A dose delivered continuously over a specific period of time.
What is the difference between Linear and Nonlinear and what both look like on a chart?
- Linear-Direct relationship beteween response and dose(Straight Line)
- Non-Linear-Curved Line
What is the difference between Threshold and Non-threshold and what both look like on a chart?
- Threshold-Refers to the point at which a response to radiation first occurs
- Non-Threshold-dose response will begin to occur at any dose regardless of size
Why fractionation and protraction benefit the patient during radiation therapy?

Causes less effect b/c time is allowed for intracellular repair and tissue recovery.
When humans are most radiosensitive during their
lifetimes?

Before birth and when older
What is the curve that has a radiation response at any given dose?

Non-threshold
What is LET and it's characteristics?
- Linear Energy Transfer-Measure of the rate at which energy is transferred from ionizing radiation to soft tissue/
- AKA-Radiation Quality
- Expressed in units of kiloelectron volt
What is RBE and it's characteristics?
- Relative Biologic Effectiveness
- Average 250 kVp
What are the DX values for LET and REB
- LET-3
- RBE-1
What is the law of Bergonie and Tribondeau?
- The radiosensitivity of living tissue varies with maturation and metabolism.
- PG 513, 33-1
What is hormesis?

An idea tgat a little bit of radiation is good for you. By stimulating hormonal and immune responses to other toxic environemntal agents(ALARA)
What conditions are tissue more radiosensitve?
- When irradiated in an oxygenated (aerobic) states
- Recovery-
- Chemical Agents-
- Hormesis PG 515-516
What is the relationship between LET and RBE?

As LET increases the ability to produce biologic damage increases.
What are the characterisitics of x-radiation?
What method expresses radiation quality?

It is expressed by LET

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JenniferHodges

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Radiation Biology

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Jennifer Hodges

Updated

2010-12-02T03:21:16Z