Radiation Biology

Question 1

What is radiation biology?

Answer 1

the study of the effects of ionizing radiation on living tissue

Question 2

Dr. Rollins

Answer 2

was researching harmful effects of radiation in 1898

Question 3

Absorption

Answer 3

total transfer of energy from the x-ray photon to patient tissues

Question 4

What is the overall concept of radiation injury?

Answer 4

chemical changes occur due to exposure to radiation and biological damage results

Question 5

Ionization mechanism

Answer 5

result in formation of a positive atom and a dislodged negative electron, occurs when x-rays strike patient tissues
*kinect energy of electron results in further ionization, excoriations or breaking of molecular bonds
*chemical changes resulting in biological damage

Question 6

What is a free radical?

Answer 6

uncharged/neutral atom or molecule existing with a single unpaired electron in its outermost shell
*highly reactive and unstable

Question 7

Free radical formation mechanism

Answer 7

when xray photon ionizes water (primary component of living cells)
result in formation of hydrogen and hydroxyl free radicals
*free radicals combine with each other to form toxins

Question 8

What is the primary mechanism that x-radiation causes damage through?

Answer 8

Free radical formation

Question 9

Direct theory of radiation injury

Answer 9

ionizing radiation directly hits critical areas within the cell, causes cell damage (DNA damage)
*occurs infrequently, most photons pass through the cell and cause little or no damage

Question 10

Indirect theory of radiation injury

Answer 10

xray photons absorbed within the cell and cause formation of toxins
occurs frequently since 70-80% cell is water
*free radical formation and combining to form toxins results in indirect injury

Question 11

Dose-response curve

Answer 11

relationship between an effect of an drug and the amount of drug given
-linear NONTHRESHOLD relationship
-determines hazardous level of drug
-drug=x-radiation
-response= damage of tissues produced
-dose=amount of radiation received

Question 12

Threshold dose

Answer 12

point at which effects are first seen
*threshold dose level does not exist for xradiation, no matter how small the amount, some biological damage will occur

Question 13

Herman Joseph Muller

Answer 13

-researched radiation induced mutations
-studied how radiation produces its biological effects
-Nobel prize in physiology/medicine in 1946

Question 14

Stochastic effects

Answer 14

-direct function of the dose
-no dose threshold; doesn’t depend on magnitude

ex// cancers, genetic mutations

Question 15

Nonstochastic/deterministic effects

Answer 15

-somatic effects
-has a DOSE THRESHOLD; effects increase in severity with increase of absorbed dose

ex// skin erythema, loss of hair, radiation sickness, decreased fertility, cataract formation

Question 16

Latent period

Answer 16

elapsed time between exposure to radiation and appearance of clinical signs
-depends on total dose received and amount of time it took to receive dose

Question 17

Period of injury

Answer 17

variety of cellular injuries may result including…
-cell death
-changes in cell function
-abnormal mitotic activity

Question 18

Recovery period

Answer 18

cells can repair damage caused by radiation, not all cellular injuries are permanent

Question 19

Cumulative effects of radiation

Answer 19

-effects of radiation exposure are additive
-body never returns to original state
-leads to health problems such as cancer, cataract formation, birth defects

Question 20

List the determining factors for radiation injury

Answer 20

-total dose
-dose rate
-amount of tissue irridated/exposed
-cell sensitivity
-age

Question 21

Short-term effects

Answer 21

larges doses of radiation absorbed within short period of time
-effects are seen within minutes day or weeks after exposure
-acute radiation syndrome (ARS): nausea vomiting diarrhea hair loss hemorrhage
*usually NOT applicable to dentistry

Question 22

Long-term effects

Answer 22

small doses of radiation absorbed over a long period of time
-effect are seen years, decades, or generations after cumulative exposure
-cancer, birth anomalies, genetic defects

Question 23

Somatic effects

Answer 23

somatic cells: all the cells in body except reproductive cells
occurs in an irridated person, changes in somatic cells, cancer, leukemia, and cataracts
*do NOT transfer to future generations

Question 24

Genetic effects

Answer 24

not seen in irradiated person
passed on to future generations
cannot be repaired

Question 25

List the factors that influence a cells response to radiation exposure

Answer 25

-mitotic activity (cells that divide frequently are more sensitive)
-cell differation (immature or highly specialized cells are sensitive)
-cell metabolism (higher metabolism are more sensitive)

Question 26

List the radiosensitive cells/structures

Answer 26

-blood cells *small lymphocyte most sensitive
-immature reproductive cells
-young bone cells

Question 27

List the radioresistant cells/structures

Answer 27

-bone cells
-muscle cells
-nerve cells

Question 28

List the radiosensitive organs/tissues

Answer 28

-lymphoid tissue
-bone marrow
-testes
-intestines
-composed of radiosensitive cells

Question 29

List the radioresistant organs/tissues

Answer 29

-salivary glands
-kidneys
-liver

Question 30

Critical organs in dental radiography

Answer 30

exposed to more radiation than others; it damages, severely diminishes quality of life
-located in head and neck region
skin
thyroid gland
lens of the eye
bone marrow

Question 31

List the disorders resulting from cumulative radiation exposure to certain structures

Answer 31

bone marrow - leukemia
reproductive cells - genetic mutations
salivary gland - carcinoma
thyroid - carcinoma
skin - carcinoma
lens of eye - cataracts