Week3 D2. Ch1&3 Rad History & Biolgy

Question 1

Ionization

Answer 1

IONIZATION
• X-rays are a form of ionizing radiation
• When x-rays strike a client, ionization results
• Chemical changes occur within the cell thus causing biological damage
Ionization is produced through photoelectric effect or
Compton Scatter
Results in the formation of a positive atom and a dislodged
negative electron
• Electron interacts with other atoms giving off kinetic energy and causing further ionization

Question 2

Free radical Formation

Answer 2

FREE RADICAL FORMATION
• Primary means by which x-radiation causes cell damage
• Occurs when an x-ray photon ionizes water (primary component of living cells)
• Water lonization = hydrogen + hydroxyl free radicals
FREE RADICALS
• Uncharged (neutral) atoms or molecules that exists with single, unpaired electron in its outermost orbit (shell)
• It possess characteristics of unstability and high reactivity
• It will bind and recombine to regain stability
• Believed to be involved in degenerative diseases and cancers.

Question 3

Direct Theory

Answer 3

DIRECT THEORY
.There is evidence of cell damage as a result of ionizing,
radiation targeting critical areas
•Ex, x-ray photon directly striking DNA cell causing injury to an irradiated organism
• Occurs infrequently
•Most x-ray photons pass through the cell and cause little damage

Question 4

Indirect Theory

Answer 4

INDIRECT THEORY
• X-ray photons are absorbed within cell causing toxins thus damaging the cell
• Free radicals combine to form toxins causing cellular dysfunction and biological injury
• Damage is not a result of a direct “hit” by x-ray photons
• Occurs frequently because of the high water content in the cells (70 - 80% water)

Question 5

DOSE-RESPONSE CURVE &
RADIATION INJURY

Answer 5

• Correlates the response and damage of tissues with the dose or amount of radiation received
• In dental radiography, although the doses received by the patient are low, damage does occur
• There is no safe amount of radiation exposure

Question 6

Threshold Curve

Answer 6

THRESHOLD CURVE
• Indicates that below a certain level (threshold), no response is evident

Question 7

Linear Curve

Answer 7

LINEAR CURVE
•Indicates that the response is proportional to the dose

Question 8

Linear Non-Threshold Curve

Answer 8

LINEAR NON-THRESHOLD CURVE
•Indicates that a response is seen at any dose

Question 9

Pics all curves

Answer 9

Question 10

STOCHASTIC:

Answer 10

randomly determined; having a random probability distribution or pattern that may be analyzed statistically but may not be predicted precisely.

Question 11

Latent vs injury

Answer 11

Question 12

RECOVERY PERIOD

Answer 12

• Not all cellular radiation injuries are permanent
• Cellular repair follows cellular damage
• Most of the damage caused by low- level radiation is repaired within the cells of the body
• Radiation effects are cumulative e: damage that remains unrepaired accumulates in the tissues
• Cumulative radiation effects include: cancer, cataract formation, birth defects

Question 13

TOTAL
DOSE

Answer 13

Refers to the quantity of radiation received, or the total
amount of radiation energy absorbed.
• MORE DAMAGE OCCURS WHEN LARGE
QUANTITIES OF RADIATION ARE ABSORBED BY A
TISSUE

Question 14

Dose Rate

Answer 14

DOSE RATE
• Refers to rate at which exposure to radiation occurs and absorption takes place
• More radiation damage occurs because of higher dosage rates - the cells need time to heal themselves!
• Genetic and somatic cells make up tissues of human body
GENETIC CELLS
• Reproductive Cells (ova, sperm)
• Undergo cell mutation ie: cannot repair themselves
•Not seen in the individual who is irradiated but rather in future offspring

Question 15

Dose rate SOMatic cells

Answer 15

SOMATIC CELLS
•Consist of all other cells other than reproductive
•Ex: cells of skin, hair, blood, glands, bone, nerves, muscles
• Do not undergo cell mutation le: are able to heal themselves up to a certain point
• A given dose of radiation is less dangerous if administered in two smaller doses than
one
larger one
•Allowing time to elapse between doses allows somatic cells to repair themselves
• Effects include cancer, leukemia, cataracts

Question 16

Radiosensitive

Answer 16

RADIOSENSITIVE
• A cell sensitive to radiation ex: small lymphocyte, bone marrow, reproductive

Question 17

Radio resistant

Answer 17

RADIORESISTANT
• A cell resistant to radiation ex: muscle, nerve, mature bone
• Refer to pg. 35 in 5th edition *** page 25 in 6th edition

Question 18

RADIATION MEASUREMENTS

Answer 18

ROENTGEN (COULOMB)
• The roentgen measures the energy produced by gamma radiation in a cubic centimeter of air. - measures radiation
exposure
• It is usually abbreviated with the capital letter “R”.
• A milliroentgen, or “mR”, is equal to one one-thousandth of a roentgen.
• An exposure of 50 roentgens would be written “50 R”.

Question 19

Rad (gray)

Answer 19

• Radiation Absorbed Dose recognizes that different materials that receive the same exposure may not absorb the same amount of energy - amount of energy absorbed by a tissue
• A rad measures the amount of radiation energy transferred to some mass of material, typically humans.
• One roentgen of gamma radiation exposure results in about one rad of absorbed dose.

Question 20

REM

Answer 20

• Roentgen Equivalent Man (rem) is a unit that relates the dose of any radiation to the biological effect of that dose. - different types of radiation have different effects on tissues.
To relate the absorbed dose of specific types of radiation to their biological effect, a “quality factor” must be multiplied by the dose in rad, which then shows the dose in rems.
• For gamma rays and beta particles, 1 rad of exposure results in 1 rem of dose.