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RT 140 Ch.5
Radiation Protection
| Question | Answer |
|---|---|
| Radiobiology | Concerned with effects of ionizing radiation on living systems |
| Adverse effects of ionizing radiation effect? | *Cell structure *Cell composition *Cell function |
| What are the attributes of ionizing radiations? | *Charge *Mass *Energy |
| What is used to Determine the extent different radiation modalities transfer energy into biologic tissues? | *Linear Energy Transfer (LET) *Relative Biological Effectiveness (RBE) *Oxygen Enhancement Ratio (OER) |
| Linear Energy Transfer (LET) | The average energy deposited per unit path length of “track” as it traverses a material medium. |
| What is an important factor in assessing potential tissue and organ damage from ionizing radiation? | Linear Energy Transfer (LET) |
| x & gamma radiation, no charge, Sparsely ionizing and interacts randomly along it’s trak, & cause damage through Indirect Action is know as what type of LET? | Low LET |
| Ionizing radiation with mass and charge, Densely Ionizing along track, Alpha Particles, Heavy Nuclei Ions, Charged Particles, Neutrons are know as what type of LET? | High LET |
| What is the formula for Linear Energy Transfer (LET)? | LET is inversely proportional to the square of the velocity and is directly proportional to the square of the charge |
| What is the size of DNA? | 10nm |
| Electron vs. Alpha | *e- represents Compton or Photoelectric effect in Diagnostic Beam *Alpha represents particles ejected from radioactive decay (Radon) |
| Relative Biological Effectiveness (RBE) | A term relating the ability of radiations with different LET's to produce a specific biologic response |
| what is the formula for RBE? | RBE = Dose in Gy from 250 kV x-rays/ Dose in Gy from another radiation that produces the same biologic effect |
| Oxygen Enhancement Ratio (OER) | Many chemicals can change the response of cells to radiation. the one that has a very big effect and is important in Radiobiology is oxygen. |
| What is a radiosensitizer and its effects have been observed in all classes of organisms? | oxygen |
| When is oxygen most effective? | Oxygen is most effective when administered simultaneously with the radiation. |
| What is the formula for Oxygen Enhancement Ratio (OER)? | OER= Hypoxic/ Oxygenated |
| Effects of Ionizing Radiation where observed in what 3 levels? | *Molecular *Cellular *Organic |
| Any induced injuries on living systems by radiation is a consequence of damage at what level? | The molecular level |
| Direct Action | Biologic Damage as a result of ionization of atoms on master molecule |
| Indirect Action | Effects produced by reactive free radicals |
| How are free radicals produced? | Free radicals produced by interaction of radiation with water. * Interaction with water molecules in the cell to produce free radicals (hydroxyl radical) that damage critical targets on DNA *H2O→ H2O+ + e- *H2O+ + H2O → H3O+ + OH- |
| What are extremely reactive and can undergo a number of reactions? | Free Radicals |
| Single Strand Breaks | *Point Mutation *Radiation can rupture chemical bonds *Can sever Sugar Phosphate (Strand) chain |
| What break is common with Low LET radiation & damage can be reversible by repair enzymes? | Single Strand Breaks |
| Double Strand Break | *Further exposure to radiation results in additional breaks on *Sugar Phosphate chain DSB on same chain are not easily repaired |
| What break is common with High LET radiation & damage to Nitrogenous bases? | Double Strand Break |
| Chromosomal Damage is associated with what type of LET? | High LET |
| Damage is only seen at what phase of Mitosis? | Metaphase and Anaphase |
| What is the irreplaceable master molecule in cell? | DNA |
| Instant Death | 1000Gy received secs to mins will disrupt the cell and cause death. |
| Reproductive Death | 1- 10Gy Cells does not die , but loses reproductive abilities |
| Apoptosis | *Cell dies without attempting to divide during Interphase *Programmed cell death |
| Mitotic Death | Retards the mitotic process and adversely affects cellular division |
| Mitotic Delay | 0.01 Gy at beginning of division can cause mitotic delay No known cause. |
| Chromosome Breakage | Cell irradiation during mitosis can lead to chromosomal breakage. |
| Survival Curves | Relates sensitivity of a particular type of cell to ionizing radiation. |
| Bergonie and Tribondeau | Radiation has a more damaging effect on cells that are: -Rapidly dividing -Have Long Mitotic Cycle -Immature stage in development Undifferentiated cells |
| Most Sensitive | M phase of cell cycle. *G2 phase |
| Least sensitive | S phase of cell cycle. *GI phase |
| Law of Bergonie and Tribondue-1906 | Established that Radiosensitivity is a function of the metabolic state of cell while irradiating Germ cell studies |
| Radiosensitivity | *Directly proportional to reproductive activity *Inversely proportional to degree of differentiation |
| Hematologic Depression | 0.25 Gy delivered lead to depressed blood count |
| Immature Blood Cells | Irradiated Bone Marrow(BM) lead to depressed stem or precursor cells. |
| Repopulation | BM cells can repopulate if low dose received |
| Radiation affects mainly what cells of Hematopoietic System? | stems cells |
| What is the Lethal Dose of radiation in animals? | LD 50/30 *30 Gy for Newts |
| What is the Lethal Dose of radiation for humans? | LD 50/60 *3-4 Gy |
| Granulocytes | *“Scavenger” WBC *Increase in number in response to irradiation *Then decrease rapidly, then decrease slowly |
| Thrombocytes (Platelets) | *Blood clotting and prevent Hemorrhaging *Lifespan of 30 days *50 rads (0.5Gy) |
| Cell Survival Curves | *With Low LET radiation, a shoulder to the curve at lower doses indicates the cells ability to repair some damage at low doses. *High-LET radiation typically has no shoulder, indicating that little or no repair takes place. |
| The greatest concern when internal contamination is possible when a radionuclide has been? | *Implanted *Ingested *Injected *Inhaled |
| What are the two types of Chromosomal Anomalies observed at metaphase? | 1. Chromosomal aberrations 2. Chromatid aberrations |
Created by:
kayg
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