DENT 1050 Chapter 4

Question 1

The latent period in radiation biology is the time between:

a. exposure of film and development
b. subsequent doses of radiation
c. cell rest and cell mitosis
d. exposure to x-radiation and clinical symptoms
e. none of the above

Answer 1

d. exposure to x-radiation and clinical symptoms

Question 2

A free radical:

a. is an uncharged molecule
b. has an unpaired electron in the outer shell
c. is highly reactive and unstable
d. combines with molecules to form toxins
e. all of the above

Answer 2

e. all of the above

Question 3

Direct radiation injury occurs when:

a. x-ray photons hit critical targets within a cell
b. x-ray photons pass through the ell
c. x-ray photons are absorbed and form toxins
d. free radicals combine to form toxins
e. none of the above

Answer 3

a. x-ray photons hit critical targets within a cell

Question 4

Indirect radiation injury occurs when:

a. x-ray photons hit critical targets within a cell
b. x-ray photons pass through the cell
c. x-ray photons are absorbed and form toxins
d. x-ray photons hit the DNA of a cell
e. none of the above

Answer 4

c. x-ray photons are absorbed and form toxins

Question 5

Which of the following relationships describes the response of tissues to radiation?

a. linear
b. linear, threshold
c. linear, nonthreshold
d. nonlinear, nonthreshold
e. none of the above

Answer 5

c. linear, nonthreshold

Question 6

Which of the following factors contributes to radiation injury?

a. total dose
b. dose rate
c. cell sensitivity
d. age
e. all of the above

Answer 6

e. all of the above

Question 7

Which of the following statements is correct?

a. Short-term effects are seen with small amounts of radiation absorbed in a short period.
b. Short-term effects are seen with small amounts of radiation absorbed in a long period.
c. Long-term effects are seen with small amounts of radiation absorbed in a short period.
d. Long-term effects are seen with small amounts of radiation absorbed in a long period.
e. None of the above

Answer 7

d. Long-term effects are seen with small amounts of radiation absorbed in a long period.

Question 8

Radiation injuries that are not seen in the person irradiated but that occur in future generations are termed:

a. somatic effects
b. genetic effects
c. cumulative effects
d. short-term effects
e. long-term effects

Answer 8

b. genetic effects

Question 9

Which of the following is most susceptible to ionizing radiation?

a. bone tissue
b. small lymphocyte
c. muscle tissue
d. nerve tissue
e. epithelial tissue

Answer 9

b. small lymphocyte

Question 10

The sensitivity of tissues to radiation is determined by:

a. mitotic activity
b. cell differentiation
c. cell metabolism
d. all of the above
e. none of the above

Answer 10

d. all of the above

Question 11

Which of the following is considered radioresistant?

a. immature reproductive cells
b. young bone cells
c. mature bone cells
d. none of the above

Answer 11

c. mature bone cells

Question 12

An organ that, if damaged, diminishes the quality of an individual’s life is termed a:

a. critical organ
b. somatic organ
c. cumulative organ
d. radioresistant organ
e. none of the above

Answer 12

a. critical organ

Question 13

The traditional unit for measuring x-ray exposure in air is termed:

a. the gray
b. coulombs per kilogram
c. the rem
d. the rad
e. the roentgen

Answer 13

e. the roentgen

Question 14

Which of the following radiation units is determined by the quality factor (QF)?

a. the roentgen
b. the rad
c. the rem
d. the gray
e. coulombs per kilogram

Answer 14

c. the rem

Question 15

The unit for measuring the absorption of x-rays is termed:

a. the roentgen
b. the rad
c. the rem
d. quality factor
e. the sievert

Answer 15

b. the rad

Question 16

Which of the following conversions is correct?

a. 1 R = 2.58 x 10^-4 C/kg
b. 1 rad = 0.1 Gy
c. 1 rem = 0.1 Sv
d. 1 Gy = 10 rads
e. 1 Sv = 10 rems

Answer 16

a. 1 R = 2.58 x 10^-4 C/kg

Question 17

Which of the following traditional units does not have an SI equivalent?

a. the roentgen
b. the rad
c. the rem
d. quality factor
e. none of the above

Answer 17

a. the roentgen

Question 18

Which of the following is used only for x-rays?

a. the sievert
b. the gray
c. the rem
d. the rad
e. the roentgen

Answer 18

e. the roentgen

Question 19

Which of the following conversions is correct?

a. 1 R = 2.58 x 10^-4 C/kg
b. 1 Gy = 100 rads
c. 1 Sv = 100 rems
d. 1 rem = rads x QF
e. all of the above

Answer 19

e. all of the above

Question 20

What is the average dose of background radiation received by an individual in the United States?

a. 0-100 mrads (0-0.001 Gy)
b. 50-100 mrads (0.0005-0.001 Gy)
c. 150-300 mrads ((0.0015-0.003 Gy)
d. 200-500 mrads (0.002-0.005 Gy)
e. 500-1000 mrads (0.005-0.01 Gy)

Answer 20

c. 150-300 mrads ((0.0015-0.003 Gy)

Question 21

What is the greatest contributor to artificial radiation exposure?

a. radioactive materials
b. medical radiation
c. consumer products
d. weapons production
e. nuclear fuel cycle

Answer 21

b. medical radiation

Question 22

The amount of radiation exposure an individual receives varies depending on:

a. film speed
b. collimation
c. technique
d. exposure factors
e. all of the above

Answer 22

e. all of the above

Question 23

A single intraoral radiograph (D-speed film, 70 kVp, long PID) results in a mean surface exposure of:

a. 50 mR
b. 250 mR
c. 500 mR
d. 1 R
e. 5 R

Answer 23

a. 50 mR

Question 24

What is the dose at which leukemia induction is most likely to occur?

a. 500 mrads (0.005 Gy)
b. 1000 mrads (0.01 Gy)
c. 2000 mrads (0.02 Gy)
d. 5000 mrads (0.05 Gy)
e. none of the above

Answer 24

d. 5000 mrads (0.05 Gy)

Question 25

Which of the following statements is incorrect?

a. X-radiation is not harmful to living tissues.
b. Dental radiographs benefit the patient.
c. In dental radiography, the benefit of disease detection outweighs the risk of damage from radiation.
d. Radiography should be prescribed only when the benefit outweighs the risk.
e. Biologic damage results from x-ray exposure.

Answer 25

a. X-radiation is not harmful to living tissues.

Question 26

Radiation biology

Answer 26

the study of the effects of ionizing radiation on living tissue

Question 27

Ionization

Answer 27

produced through the photoelectric effect or Compton scatter and results in the formation of a positive atom and a dislodged negative electron.

Question 28

Free radical with no charge

Answer 28

denoted by a dot following the chemical symbol

Question 29

Free radical

Answer 29

an uncharged (neutral) atom or molecule that exists with a single, unpaired electron in its outermost shell; highly reactive and unstable

Question 30

Direct theory

Answer 30

suggests that cell damage results when ionizing radiation directly hits critical areas, or targets, within the cell

Question 31

Indirect theory

Answer 31

suggests that x-ray photons are absorbed within the cell and cause the formation of toxins, which, in turn, damage the cell

Question 32

Dose-response curve

Answer 32

can be used to correlate the “response,” or damage, of tissues with the “dose,” or amount, of radiation received

Question 33

Stochastic effects

Answer 33

occur as a direct function of dose

Question 34

Nonstochastic effects

Answer 34

(deterministic effects) somatic effects that have a threshold and that increase in severity with increasing absorbed dose

Question 35

Latent period

Answer 35

the time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs

Question 36

Length of latent period

Answer 36

the more radiation received and the faster the dose rate, the shorter the latent period

Question 37

Period of injury

Answer 37

comes after latent period; includes: cell death, changes in cell function, breaking or clumping of chromosomes, formation of giant cells, cessation of mitotic activity, and abnormal mitotic activity

Question 38

Recovery period

Answer 38

last event in radiation injury; depending on a number of factors, cells can repair the damage caused by radiation

Question 39

Cumulative effects

Answer 39

effects of radiation are additive and if unrepaired damage accumulates in tissues; can lead to cancer, cataract formation, birth defects, etc.

Question 40

Total dose

Answer 40

quantity of radiation received, or the total amount of radiation energy absorbed

Question 41

Dose rate

Answer 41

rate at which exposure to radiation occurs and absorption takes place (dose rate = dose/time)