LO2

Question 1

What 2 regulations come under the Health and Safety at Work Act (1974)?

Answer 1

• Ionising Radiation Regulations (1999)

- Ionising Radiation (Medical Exposure) Regulations (2000)

Question 2

What is the Ionising Radiation Regulations (1999)?

Answer 2

Concerned with protection of staff.

The radiation protection supervisor (RPS) ensures that the practice complies with IRR 1999 and the local rules.
The radiation protection adviser (RPA) is an expert in radiation protection who can guide the practice RPS with regard to compliance and regulations.

Question 3

What is the Ionising Radiation (Medical Exposure) Regulations (2000)?

Answer 3

Concerned with protection of patients.

It requires that all practitioners and operators who take dental radiographs and expose patients to radiation should be adequately trained.

Question 4

What is excitation?

Answer 4

Raising of electron in atom to higher energy level without actual ejection of electron.
- Causes no biological change.

Question 5

What is ionisation?

Answer 5

If radiation has enough energy, it can eject electrons.

- Cell’s molecular structure has changed – left with electron and positive ion.

Question 6

What are the direct effects of ionisation?

Answer 6

X-ray photons interact with macromolecules (DNA, RNA, proteins, enzymes).

Question 7

How do direct effects of ionisation occur?

Answer 7

▪ Radiation interacts directly with critical target.
▪ Deposits energy.
▪ Ionisation/excitation of atoms of critical target.
▪ Breaking of chemical bonds.
▪ Chain of events that lead to biological change in critical target.
▪ Damage to DNA = point mutation – effects include:
• Inability to pass on information.
• Abnormal replication.
• Cell death.
• Only temporary damage – DNA repaired successfully before further cell division.

Question 8

What are the indirect effects of ionisation?

Answer 8

Photon disrupts water molecule into reactive free radicals that damage DNA.

Question 9

How do the indirect effects of ionisation occur?

Answer 9

▪ Interacts with other atoms/molecules in cell (water) to produce free radicals.
▪ Free radicals = highly reactive and displace other atoms (breaks chemical bond) to become neutral.
• Damage DNA.
• OH— + OH— —> H2O2 (toxic to cell).
• H— + O2 —> HO2— (biological damage to cell).

Question 10

What are hereditary effects?

Answer 10

Effects in subsequent generations due to gonad irradiation – no evidence in human generations.

Question 11

What are somatic effects?

Answer 11

Effects seen in person irradiated:
- Short-term or long-term after exposure.

Can be deterministic or stochastic.

Question 12

What are deterministic effects?

Answer 12

Non-dental related.

Dose related – larger the dose, greater severity of effect.
▪ Effect doesn’t occur below threshold.
▪ Examples:
• Cataract formation.
• Loss of fertility.
• Erythema of skin.
• Radiation sickness.

Question 13

What are stochastic effects?

Answer 13

Dental related.

Severity is not dose related.
▪ No known threshold.
▪ Probability of effect occurring increases with dose.
▪ Example: - cancer/tumour.

Question 14

What is radio-sensitivity of cell affected by?

Answer 14

• Amount of energy transferred.
• Cell cycle.
• Presence/absence of oxygen.
• Type of cell.

Question 15

How does the amount of energy transferred affect radio-sensitivity of cell?

Answer 15

o Linear Energy Transfer (energy deposited per unit of track length):
▪ Different particles deposit different amounts of energy (protons deposit more than alpha particles).
▪ Higher the LET, closer together reactions.
• Several OH— molecules can be close and increase chance of H2O2 production.

Question 16

How does cell cycle affect radio-sensitivity of cell?

Answer 16

o Cells in S phase = most resistance.
o Cells in G2 and mitosis = most sensitive.
▪ Construction of spindle and chromosomes condense.
▪ DNA unravelled and exposed.
▪ Less time to repair damage before cell divides.

Question 17

How does oxygen affect radio-sensitivity of cell?

Answer 17

Oxygen reacts with free radicals:
R— + O2 —> RO—2

Oxygen fixes radiation damage RO—2 = unrepairable.

Question 18

How does type of cell affect radio-sensitivity of cell?

Answer 18

o Radiosensitivity function of metabolic state of cell.
o Law of Bergonie and Tribondeau states that cell’s radiosensitivity is:
▪ Directly proportional to their reproductive activity.
▪ Inversely proportional to their degree of differentiation.

Question 19

What are the responses of cell radiation?

Answer 19

Cell death.
DNA strand breaks (single or double strand):
- These are the critical lesions in radiation cell killing.
- Number of lesions increases with dose of radiation.

Question 20

Why would a film need to be duplicated?

Answer 20

If it needs to be sent to another dentist, specialist or obtain preauthorisation from insurance company.

Question 21

What are the principles of patient protection?

Answer 21

Justification.
Optimisation.
Limitation.

Question 22

What is justification?

Answer 22

Exposure kept as low as possible for public.

Patient only has if clinically necessary – benefits outweigh risks.

Question 23

What is optimisation?

Answer 23

Keep radiation exposure and consequent dose to lowest level.

Question 24

What is limitation?

Answer 24

Dose shouldn’t exceed appropriate limits.

Question 25

Name 3 physical protection techniques

Answer 25

• Time
• Distance
• Shielding

Question 26

How does time work in protection?

Answer 26

Patients:

• Limit exposure to X-rays.
• Limit no. of X-rays/views.

Staff:

• Limit time in high dose areas.
• Monitor exposure.

Question 27

How does distance work in protection?

Answer 27

Dose of X-ray is reduced when staff stand further away.

Question 28

How does sheilding work in protection?

Answer 28

Protects patient and self from scattered radiation.

Question 29

What is quality assurance and why is it necessary?

Answer 29

• Regular testing to detect equipment malfunctions.
• Planned monitoring and schedules maintenance for consistent film processing – compare them against national diagnostic levels.
• Regular assessment of other variables that affect image quality.

It ensures that radiation doses are as low as reasonably practicable.

• Necessary to monitor patient doses on regular basis.
• X-ray equipment must comply with recommended standards.

Question 30

What is the quality rating score?

Answer 30

Score 1 – excellent.
- No errors present (minimum 70%).

Score 2 – diagnostically acceptable.
- Minimal errors present that do not prevent the radiograph from being used for diagnosis (maximum 20%).

Score 3 – unacceptable.
- Errors prevent the radiograph from being used for diagnosis (maximum 10%).

Question 31

How long should records be kept?

Answer 31

11 years for adults and children (or until they are 25 years old).