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Radiobiology
| Question | Answer |
|---|---|
| What is Radiobiology | Study of effects of ionizing radiation on biologic tissue. |
| Three of radiations harmful effects? | Skin burns(early effects), Cancer and leukemia(which may not appear for many years later, called late effects.) |
| Does diagnostic radiation cause harm? | Yes, even small doses. |
| Why do we expose ourselves and what can be done to minimize harmful effects? | When the benefits outweigh the risks. We can produce high quality radiographs w/minimal exposure. (ALARA) |
| What level is the effect of x-rays on humans? | Atomic level. Causing ionization and excitation. |
| What are the results of this deposited energy in humans? | Molecular change.Damage when a critical molecule is involved. |
| What happens to the atom that interacts with the x-ray? | It may become dislodged from it's molecule or may change positions within the molecule. |
| What can happen to the abnormal molecule? | It can function improperly or cease to function altogether. |
| What then happens to the cell with an abnormal molecule? | It can impair or even kill the cell. |
| Is the damage from radiation exposure reversible? | Yes, Atoms attract free electrons. Molecules are repaired by repair enzymes and cells and tissue can regenerate. |
| What are Early Radiation Effects? | Damage that occurs within minutes or days of exposure. Like sunburn or even death. |
| Does Early Radiation Effects occur on the diagnostic level? | No, that is more Late Effects. |
| What are Late Radiation Effects? | Damage that occurs 6 months or more after exposure. Ex: diagnostic radiation |
| What defines the nature of damage from radiation exposure? | The molecular structure of cells and tissues. |
| What are some of the most sensitive areas to radiation? | Gonadal area, thyroid and RBC's. |
| What are 5 principal types of molecules in humans? | Water-Proteins-Lipids-Carbohydrates-Nucleic Acids |
| What is the body composed of the most? | Water 80% of the body. It provides shape to cells, assist in maintaining body temp. Involved in some biochemical reactions. |
| What do proteins do for the body? | They make up 15% of the body. Long chain macromolecules made up of a combo of amino acids.They provide structure & support for muscles, enzymes, hormones and antibodies. |
| What do lipids do for the body? | Composed solely of carbon,oxygen and hydrogen. They are structural components of cell membranes. Concentration of lipids just under the skin for insulation. Store fuel for the body but hard to retreive it. |
| What are carbohydrates in the body? | They have the same atoms as lipids but different composition. These are saccharides. Monosaccharides and disaccharides are simple sugars. Polysaccharides are staches and glycogen. |
| What are the two principal nucliec acids to human metabolism? | DNA and RNA |
| Where is RNA? | Ribonucleic acid, located principally in the cell cytoplasm, is also found in the nucleus. Involved in cell growth & development through protein synthesis. Single helix molecule configuration. |
| Where is DNA and what does it do? | Deoxyribonucleic acid. In cell nucleus. The most command or control molecule for the cells function. Contains hereditary info.if its a germ cell or reproductive cell. Double helix configuration |
| What is the principle radiosensitive molecule and what is it made up of? | DNA,Very large complex molecules. Made up of a backbone of alternating deoxyribose (a sugar) and phosphate. Attached to each deoxyribose molecule is an organic base. |
| What are some organelles in the cell? | In the nucleus; DNA, RNA, nucleolus. In cytoplasm; endoplasmic reticulum, mitochondria, lysosomes and ribosomes. |
| What is the most radiosensitive part of a cell? | The nucleus. Each cell component (macromolecule) can be changed physically with a dose of 1 Mrad. |
| How many rads can change a living cell? | A few rads. Human cells can be killed with a dose less than 100 Rad. |
| What are the functions of a cell? | All have specific functions, each cell absorbs nutrients through the cell membrane to produce energy and molecular synthesis. |
| What is protein synthesis? | A critical cellular function necessary for survival. A complex process that involves many diff. molecules and cellular structures. |
| Example of Protein synthesis; | DNA has a molecular code for the proteins the cell will produce. Genetic message transferred to mRNA which leaves the nucleus & goes to ribosome. The code is then transferred to tRNA which searches the cytoplasm for the amino acids to complete the code. |
| What happens when tRNA finds the acid? | It returns to the ribosome to drop off the amino acids where it bonds w/ other amino acids to make the protein. |
| What happens when the process of protein synthesis is interrupted? | Cell damage occurs. Damage to DNA causes the most damage to the cell. |
| How many rads can disrupt cell proliferation?(reproduction of a cell or cells) | It would take many thousands of rads to interrupt cell proliferation but this can come in one single ionizing event. |
| The human body consist of two general types of cells? | Somatic (mitosis-46 chromosomes)and genetic cells(reduce & divide-23 chromosomes.Each parent cell dividesinto 4 daughter cells.). |
| During development and maturation of the human body 2 genetic cells unite and divide, what happens next? | Diff. cell types evolve, cells of similar structure and function form tissues. |
| What do tissues form? What do tissues and organs form? | Tissues are bound together to form organs. Tissue & organs combine to make systems: nervous, digestive; endocrine etc. |
| What cells are the most sensitive to radiation? | Immature cells (undifferentiated, stem cells, precurser) |
| What is the sesitivity of a cell is dependent on? | The maturity of the cell & its function. The more the cells of a tissue divide, the more radiosensitive it will be. Reproductive cells are highly sensitive. |
| What are some highly radiosensitive cell types? | Lymphocytes, spermatogonia, erythroblasts, intestinal crypt cells. |
| What are some intermediate radiosensitive cell types? | Endothelial cells, osteoblasts, spermatids and fibroblasts |
| What are some lower response cells to radiosensitivity? | Muscle cells and nerve cells. |
| What is the Law of Bergonie and Tribondeau? | The radiosensitivity of living tissue varies with maturation and metabolism. |
| Which cells are the most resistant to radiation? | The more mature, the more resistant it is. |
| Which cells are most radiosensitive? | The younger tissues and organ and the cells with a higher level of metabolic activity. |
| True or False: As the proliferation rate for cells and the growth rate for tissues increase the radiosensitivity increases. | True |
| True or False:The law states that the fetus is more radiosensitive than children or adults. | True |
| What is LET? | Linear Energy Transfer-The measurement of the rate the energy is transferred from ionizing radiation to soft tissue. |
| What units are LET measured in? | keV/um (kiloelectron volts per micrometer) LET of diagnostic x-rays = 3 keV/um |
| What happens when LET increases and what is the probability of interaction w/ target molecule(DNA) | AS LET increases, biological effect increases. The probability of interaction increases. |
| What is RBE? | Relative Biological Effectiveness - used to describe the ability to produce biologic damage. |
| What happens to RBE as LET increases? | RBE increases. |
| What is the diagnostic RBE? What does it take to kill a mouse? | Diagnostic is 1 RBE. It takes 3.1 to kill a mouse. |
| Radiation with a lower LET than diagnostic x-rays have an RBE of? | RBE less than 1. Radiation with higher LET have a higher RBE. They are drectly proportional. |
| What is Protraction? | Same dose of radiation but at a slower rate. Therefore the effect of the dose will be less than one given all at once or in a short time period. This allows for intracellular repair. |
| What is Fractionation? | Doses are given in equal divided amounts 24 hrs apart, the effect is alot less. This allows for intracellular repair. EX: Radiation therapy. Or how RT's get it. |
| What is OER? | Oxygen Enhanced Ratio. Tissue is more sensitive when irradiated in the presence of oxygen. (aerobic-oxygen vs. anoxic-very low O2 vs hypoxic-o2 deprived) |
| The formula for OER? | Dose under anoxic conditions to produce a given effect divided by dose under aerobic conditions to produce the same effect. |
| What has radiation oncology used to attempt to increase the effect of radiosensitivity? | Hyperbaric conditionsd (more oxygen) |
| Is OER LET dependent? | Yes, OER increases as LET decreases. Therefore they are inversely proportional. |
| What affects the rate of sensitivity? | Age |
| Is recovery possible of human cells? | Yes if dose is not lethal. Time in between doses gives a chance for repair. Some cells recover more readily than others. |
| Oxygen Enhanced Ratio. Tissue is more sensitive when irradiated in the presence of oxygen. (aerobic-oxygen vs. anoxic-very low O2 vs hypoxic-o2 deprived) | |
| Dose under anoxic conditions to produce a given effect divided by dose under aerobic coditions to produce the same effect. | |
| What has radiation oncology used to attempt to increase the effect of radiosensitivity? | |
| Is OER is LET dependent? | Yes, OER increases as LET decreases. Therefore they are inversely proportional. |
| Is recovery possible of human cells? | Yes if dose is not lethal. Time in between doses gives a chance for repair. Some cells recover more readily than others. |
| Recovery of cells means? | Repair and repopulation. |
| What happens when cells die? | Atrophy (a wasting away or decrease in size) occurs. In cases of radiation therapy, that is a good thing but not on good cells. |
| Chemical agent can alter the effect of radiation exposure. What are the two types? | Radiosensitizers - enhance the effect and Radioprotectors-(sulfhydryl)can reduce the effect of sensitivity needing twice the amount to do the job. None have been found for human use. They are more harmful than the radiation. |
| What does Hormesis mean? | Small quantities of lethal subjects such as radiation can be good for you, that a little stimulates the hormonal and immune responses to other toxic agents. Ex: Fluoride is deadly but in small amounts it is a known tooth preservative. |
| What is Radiation Dose-Response Relationship? | A mathematic relationship between various doses of rad. to the reponse level observed. |
| What is Linear Response? | The response directly proportional to the dose of radiation. |
| What is non-threshold? | Any dose expected to cause damage. Therefore diagnostic radiation is linear-nonthreshold. |
| What is Threshold response? | When they know what the response will be to a certain amt. of radiation. Such as in Radiation therapy. |
| What effects is diagnostic radiology most interested in? | The late effects. Not a lot of research is possible. |
Created by:
sewwhat4
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