Q: A dental x-ray exposes the thyroid gland to radiation. What is the estimated dose required to induce cancer in the thyroid, and how does this compare to typical dental exposures?

$$6000\ \text{mrad} (0.06 Gy$$); typical dental exposures are much lower

Q: Which of the following is the correct conversion between traditional and SI units for absorbed dose?

$$1\ \text{Gy} = 100\ \text{rad}$$

Question 1

Which of the following best describes the indirect theory of radiation injury?

Accepted Answer

Radiation is absorbed by water in the cell, forming free radicals that combine into toxins which damage the cell.

Question 2

A patient receives a dental x-ray. Which unit would most appropriately express the absorbed dose of radiation in SI units?

Accepted Answer

$$	ext{gray (Gy)}$$

Question 3

Which of the following tissues is considered most radiosensitive?

Accepted Answer

Bone marrow

Question 4

A linear, nonthreshold dose-response curve for radiation injury implies which of the following?

Accepted Answer

The response is directly proportional to the dose, and any dose, no matter how small, can cause damage.

Question 5

Which of the following is an example of a stochastic effect of radiation?

Accepted Answer

Cancer

Question 6

A dental patient is exposed to a small dose of radiation repeatedly over many years. Which type of effect is most likely to occur?

Accepted Answer

Long-term effect such as cancer or genetic defects

Question 7

Which of the following factors does NOT increase the severity of radiation injury?

Accepted Answer

Older age of the patient

Question 8

Which of the following best describes the difference between somatic and genetic effects of radiation?

Accepted Answer

Somatic effects include all cells except reproductive cells and are not passed to offspring; genetic effects involve reproductive cells and can be inherited.

Question 9

A dental x-ray exposes the thyroid gland to radiation. What is the estimated dose required to induce cancer in the thyroid, and how does this compare to typical dental exposures?

Accepted Answer

$$6000\ 	ext{mrad} (0.06 Gy$$); typical dental exposures are much lower

Question 10

Which of the following is the correct conversion between traditional and SI units for absorbed dose?

Accepted Answer

$$1\ 	ext{Gy} = 100\ 	ext{rad}$$

Question 11

Which of the following is a major source of natural background radiation exposure in the United States?

Accepted Answer

Radon and thoron

Question 12

A patient receives a dose of $$0.01\ 	ext{Sv}$$ during a medical procedure. Express this dose in millisieverts (mSv).

Accepted Answer

$$10\ 	ext{mSv}$$

Question 13

Which of the following best explains why children are more susceptible to radiation injury than adults?

Accepted Answer

Children have higher mitotic activity and more sensitive cells.

Question 14

Which of the following is a practical way to reduce patient exposure to radiation during dental imaging?

Accepted Answer

Using the fastest available film or digital sensors

Question 15

Which of the following is true regarding the risk of fatal cancer from dental imaging compared to other everyday risks?

Accepted Answer

The risk from dental imaging is about 3 in 1,000,000, which is much lower than the risk of spontaneous cancer.

Question 16

Which of the following best describes the cumulative effects of radiation exposure?

Accepted Answer

Unrepaired damage from repeated exposures accumulates in tissues over time.

Question 17

Which of the following is the most appropriate reason for prescribing dental images?

Accepted Answer

Only when the benefit of disease detection outweighs the risk of biologic damage

Question 18

Which of the following is a correct statement about the formation of free radicals during radiation exposure?

Accepted Answer

Free radicals are formed when x-ray photons ionize water molecules in cells.

Question 19

A patient receives 100 rads of radiation. How many grays (Gy) is this equivalent to?

Accepted Answer

$$1\ 	ext{Gy}$$

Radiation Biology: Mechanisms, Effects, and Measurement in GOB Chemistry

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