Radiology Exam 2

Front 1

effects on macromolecules

Back 1

- 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.

Front 2

cell survival curves and LET

Back 2

- High LET radiation is less lethal than low LET radiation

Front 3

cell survivla and oxygen

Back 3

- the more oxygen available the higher the cell survival rate.

Front 4

oxygen enhancement ratio

Back 4

- Dose modifying effect -

OER = dose in anoxic conditions/ dose in presence of oxygen

Front 5

age modifying factors

Back 5

- the younger the patient the more sensitive to x radiation

- tissue volume - does does not take into account the area of body being irradiated.

Front 6

relative sensitivity of cells

Back 6

- 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.

Front 7

in general (regarding relative sensitivity of cells)

Back 7

- 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.

Front 8

vegetative intermitotic cells

Back 8

- 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.

Front 9

effects of radiation on tissues

Back 9

- deterministic effect - the severity of the change is dose dependent

- stochastic effect - the probability of occurence is dose dependent

Front 10

effects of radiation therapy on the oral cavity

Back 10

- 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.

Front 11

effects or radiation... Taste buds

Back 11

- degeneration of architecture
- post 2/3rds bitter and acid affected.
- ant. 1/3rds salt and sweet affected
- regenaration 60-120 days after therapy.

Front 12

salivary gland destruction

Back 12

- destruction of parenchyma
- reduction in flow is dose dependent
- xerostomia produces changes in oral microflora, a decrease in pH causing decalcifications and radiation caries.

Front 13

radiation damage to teeth

Back 13

- irradiation during dev. may retard growth, destroy the tooth bud or cause malformations; permanent teeth are relatively radioresistant

Front 14

radiation ORN (osteoradionecrosis)

Back 14

- mandible affected more than maxilla because of poorer blood supply.

- avoid radiographs for 6 mos. after therapy

-

Front 15

LD 50/30 value

Back 15

- the dose that is lethal for 50% of the population 30 days after the exposure

Front 16

radiation syndromes

Back 16

- 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.

Front 17

bone marrow syndrome

Back 17

- 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.

Front 18

GI syndrome

Back 18

- 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.

Front 19

CNS syndrome

Back 19

- 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.

Front 20

late somatic effects

Back 20

- 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.

Front 21

late somatic effects

Back 21

- cataract induction
- 2-5 Gy

- mental retardation
- 4% incidence/ 100 mSv exposure during weeks 8-15 of gestation.