Chapter 11 - Radiobiology and Radiation Safety

Question 1

SI Units

Answer 1

SI Unit of SI Term
Exposure Air Kerma (Gy-a)
Absorbed dose Gray (Gy-t)
Dose equivalent Sievert (Sv)

Question 2

Linear energy transfer (LET)

Answer 2

Linear energy transfer (LET) is the amount of x-ray energy transferred on average, per the length of passage through the tissue. It explains how much radiation was absorbed in a given section of tissue corresponding to the path through the tissue of the x-ray photons.

Question 3

oxygen enhancement ratio (OER)

Answer 3

When there is more oxygen in the tissues, it is more sensitive to radiation compared to tissues with low oxygen. This is often referred to as the oxygen effect; the OER can measure these values.

Question 4

Law of Bergonié and Tribondeau

Answer 4

1.Age. Younger patient cells are more sensitive than older ones.
2.Differentiation. Simple cells are more sensitive than highly complex ones.
3.Metabolic rate. Cells that use energy rapidly are more sensitive than those that have a slower metabolism.
4.Mitotic rate. Cells that divide and multiply rapidly are more sensitive than those that replicate slowly.

Question 5

Long-Term Somatic Effects

Answer 5

The time required for long-term effects to become apparent is generally considered to be 5 to 30 years, with the greatest percentage of effects occurring between 10 and 15 years.

Question 6

Good communication:

Answer 6

*Encourages reduction in anxiety and emotional stress.
*Enhances the professional image of the x-ray operator as a person who cares about the patient’s well-being.
*Increases the chance for successful completion of the x-ray examination, thereby reducing the potential of repeat exposures.

Question 7

Gonad Shielding

Answer 7

Whenever the gonads are within 5cm of the margin of the radiation field, gonad dose will be significantly reduced by shielding.

Question 8

Lead Shielding

Answer 8

The minimum standard lead equivalency for the aprons should be 0.5mm and for the lead gloves should be 0.25mm. Radiographers perform this quality control check every 6 months.

Question 9

Optically stimulated luminescence (OSL)

Answer 9

uses aluminum oxide as a radiation detector. This dosimeter is processed using laser light.

Question 10

Fetus Dose

Answer 10

The NCRP-recommended monthly EqD limit to the embryo/fetus for a pregnant worker is 0.5 mSv. There is also a limit for the 9 months of the pregnancy. This limit is set at 5.0 mSv.

Question 11

Effective Dose Limits for Occupational Workers

Answer 11

mSv
Annual 50
Cumulative Age×10 mSv
Lens of the eye 150
Skin, hands, and feet 500
Embryo/fetus (months) 0.5
Entire gestation 5.0