Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
21 Cards in this Set
- Front
- Back
effects on macromolecules
|
- proteins, lipids and carb present in multiple copies
- DNA is not present in abundance so damage to this causes problems - DNA has ability to repair its self. |
|
cell survival curves and LET
|
- High LET radiation is less lethal than low LET radiation
|
|
cell survivla and oxygen
|
- the more oxygen available the higher the cell survival rate.
|
|
oxygen enhancement ratio
|
- Dose modifying effect -
OER = dose in anoxic conditions/ dose in presence of oxygen |
|
age modifying factors
|
- the younger the patient the more sensitive to x radiation
- tissue volume - does does not take into account the area of body being irradiated. |
|
relative sensitivity of cells
|
- law of bergonie and tribondeau
- radiosensitivity is directly proportional to its reproductive capacity and indirectly proportional to it degree of differentiation. - exceptions are lymphocytes and oocytes whith are very radiosensitive although they are highly differentiatied and non dividing. |
|
in general (regarding relative sensitivity of cells)
|
- the more mature a cell is the more resistant it is.
- the younger the cell the more sensitive it is. - high metabiolic activity = high sensitivity - sensitivity increases with proliferation and growth rate - most radiosensitive cells are those that have a high mitotic rate - undergo many future mitosis - are most primitive in differentiation. |
|
vegetative intermitotic cells
|
- divide regularly and are highly sensitive
- stem cells like erythroblasts and basal cells of oral mucous membrane. - differentiating intermitotic cells - divide often and undergo some differentiations , spermatogonia, lymphocytes and oocytes - multipotential connective tissue cells - divide irregularily in the response for more cells. - endothelial cells, fibroblasts and osteoblasts. - reverting post mitotic cells - divide infrequently - livercells and kidney cells. - fixed post mitotic cells - most highly differentiated and incapable of division once mature; neurons and muscle cells. |
|
effects of radiation on tissues
|
- deterministic effect - the severity of the change is dose dependent
- stochastic effect - the probability of occurence is dose dependent |
|
effects of radiation therapy on the oral cavity
|
- oral mucous membrane -
- basal cell layer is composed of vegetative intermitotic cells which are very radiosensitive - end of second week = mocositis - breakdown - pseudomembrane - candida albicans infections - patients are often put on prophylactic anti fungals such as diflucan. |
|
effects or radiation... Taste buds
|
- degeneration of architecture
- post 2/3rds bitter and acid affected. - ant. 1/3rds salt and sweet affected - regenaration 60-120 days after therapy. |
|
salivary gland destruction
|
- destruction of parenchyma
- reduction in flow is dose dependent - xerostomia produces changes in oral microflora, a decrease in pH causing decalcifications and radiation caries. |
|
radiation damage to teeth
|
- irradiation during dev. may retard growth, destroy the tooth bud or cause malformations; permanent teeth are relatively radioresistant
|
|
radiation ORN (osteoradionecrosis)
|
- mandible affected more than maxilla because of poorer blood supply.
- avoid radiographs for 6 mos. after therapy - |
|
LD 50/30 value
|
- the dose that is lethal for 50% of the population 30 days after the exposure
|
|
radiation syndromes
|
- prodromal syndrome
- 1-2 Gy, nausea, vomiting and diarea - latent period - period of apparent well being prior to expression of symptoms - length and severity of latent period is dose dependent. |
|
bone marrow syndrome
|
- expsure in 2-7 gy range
- lymphocytes and granulocytes affected first - susceptibility infection results - platelets affected next - increased bleeding - erythrocytes later - anemia - vicitims can recover with antibiotics, fluid replacement and good hospital care. |
|
GI syndrome
|
- expusre in the 7-15 Gy range
- pt. may feel well until the 5th day - affects the epithelial cells of theintestinal villi. - loss of electrolytes, hemorrhage, diarrhea and septicemia - most patients die within 14 days. |
|
CNS syndrome
|
- exposures in excess of 50gy
- instant diarrhea - very short latent period - collapse of circulation and fall in BP - necrosis of cardiac muscles and patient is dead in 1-2 days. |
|
late somatic effects
|
- carcinogenesis - leukemias evidnet after 7 years, solid tumor later (10 years)
- most important factors are dose and dose rate. - risk for children twice as great. |
|
late somatic effects
|
- cataract induction
- 2-5 Gy - mental retardation - 4% incidence/ 100 mSv exposure during weeks 8-15 of gestation. |