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Dental Radiography > Module 4 > Flashcards

Module 4 Flashcards

1
Q

Define radiation dose

A

Amount of radiation received by patients from different X-ray exams

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2
Q

Define reference dose

A

Dose level which is set for every radiographic exam.

It shouldn’t be exceeded.

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3
Q

Define radiation dose limits

A

Maximum levels of radiation to patients (only if clinically necessary)

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4
Q

Define Natural background radiation dose

A

Naturally occurring radiation from foods, radon gas, rocks, earth’s crust and space.

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5
Q

What is the natural background radiation dose calculated as in the UK per year?

A

2.23 mSv

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6
Q

What are the 3 main dose units in radiation?

A
  • Radiation absorbed dose (D)
  • Equivalent dose (Ht)
  • Effective dose (E)
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7
Q

What is the unit for Radiation absorbed dose?

A

Gray (or milligrays)

- measured in Joules/kg

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8
Q

What is the unit for Equivalent dose?

A

Sievert (or millisievert)

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9
Q

What is the unit for Effective dose?

A

Sievert (or millisievert)

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10
Q

How can you calculate the Radiation absorbed dose?

A

Dosimeter

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11
Q

How can you calculate the Equivalent dose?

A

H(t) = D x W(r)

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12
Q

How can you calculate the Effective dose?

A

E = H(t) x W(t)

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13
Q

Define Radiation absorbed dose

A

Measure of the amount of energy absorbed from the radiation beam per unit mass of tissue

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14
Q

Define Equivalent dose

A

Measure that indicates the different radio-biological effectiveness of different types of radiation.

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15
Q

Define Effective dose

A

Measure that allows doses from different investigations of different parts of the body to be compared.

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16
Q

What does W(t) stand for?

A

Tissue weighting factor

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17
Q

What is the W(t) for bone marrow?

A

0.12

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18
Q

What is the W(t) for salivary glands?

A

0.01

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19
Q

What is the W(t) for gonads?

A

0.08

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20
Q

What is the W(t) for breast?

A

0.12

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21
Q

What is the W(t) for lungs?

A

0.12

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22
Q

What is the W(t) for thyroid?

A

0.04

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23
Q

What is the W(t) for skin?

A

0.01

24
Q

What is the W(t) for oesophagus?

A

0.05

25
Q

What is the W(t) for bone surface?

A

0.01

26
Q

What is the W(t) for brain?

A

0.01

27
Q

What is the W(t) for oral mucosa?

A

0.12

28
Q

What is the effective dose for a bitewing/PA radiograph?

A

0.0003-0.022 mSv

29
Q

What is the effective dose for an OPG?

A

0.0027-0.038 mSv

30
Q

What is the effective dose for an upper standard occlusal?

A

0.008 mSv

31
Q

What is the effective dose for a lateral cephalometric radiograph?

A

0.0022-0.0056 mSv

32
Q

What is the effective dose for a skull radiograph (PA)?

A

0.02 mSv

33
Q

What is the effective dose for a skull radiograph (lateral)?

A

0.016 mSv

34
Q

What is the effective dose for a head CT?

A

1.4 mSv

35
Q

What is the effective dose for a mandible/maxilla CT?

A

0.25-1.4 mSv

36
Q

What is the effective dose for a barium swallow?

A

1.5 mSv

37
Q

What is the effective dose for a barium enema?

A

2.2 mSv

38
Q

What is the effective dose for a CBCT (dento-alveolar)?

A

0.01-0.67 mSv

39
Q

What is the effective dose for a CBCT (craniofacial)?

A

0.03-1.1 mSv

40
Q

How can the dose be reduced?

A
  • Change speed of film to faster speed.
  • Use 70kV equipment.
  • 200mm fsd.
  • Rectangular collimator to produce rectangular beam.
41
Q

What % of X-rays taken each year are dental?

A

40%

42
Q

What should the reference dose be of a mandibular molar PA for an adult?

A

4 mGy per millimeter

43
Q

What should the reference dose be for an adult OPG?

A

65 mGy per millimeter

44
Q

How does the reference dose aim to protect patients?

A

Identifying high dose equipment that can be adjusted or taken out of service.

45
Q

True or false: The effective dose takes into account the part of the body being irradiated?

A

True

46
Q

What statements are true of:

‘the risks of ionising radiation’ ?

A
  • If 1 million patients had an OPG radiograph, approximately one excess cancer would be expected.
  • The risk of radiation-induced cancer is increased as radiation dose increases.
47
Q

What number of patients can be expected to get cancer per year for intra-oral radiographs?

A

1 in 2 million exposures = cancer.

1 in 20 million exposures = cancer (with modern 70kV, fast E speed films = lower dose).

48
Q

What are some examples of radiation dosimeters?

A
  • Thermo-Luminescent Dosimeters (TLD) or film badges.

- Electronic dosimeter.

49
Q

What does justification, optimisation and limitation mean?

A
  • Justification = benefit of radiograph must outweigh the risks (only if clinically necessary).
  • Optimisation = ALARP.
  • Limitation = Dose shouldn’t exceed appropriate limits.
50
Q

What are the 3 groups that the population is divided into?

A
  • Patients
  • Radiation workers
  • Public
51
Q

What are the dose limits for patients?

A

No set dose limit

52
Q

What are the dose limits for radiation workers?

A

Classified workers (those in nuclear power industry) = 20 mSv.

Non-classified workers (dental) = 6 mSv

53
Q

What are the dose limits for the general public?

A

1 mSv

54
Q

What is the estimated number of fatal malignancies per year in the UK associated with dental radiography?

A

10-12

55
Q

What is the estimated number of genetic stochastic effects (dental radiography) in the UK?

A

1 congenital abnormality every 3 years

56
Q

Who is more at risk with radiographs: younger or elderly patients?

A

Younger

Dental Radiography (5 decks)

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