Radiology 5

Question 1

Two biological effects of radiation

Answer 1

Deterministic and non-deterministic

Question 2

Deterministic

Answer 2

Non-stochastic: those we know will occur.
Threshold dose (known)
Somatic effects.

Question 3

Non-deterministic

Answer 3

Stochastic: those which may occur.
Down to chance, no threshold (unknown).

Question 4

How can somatic effects be used clinically

Answer 4

Patient treated for cancer with radiotherapy

Question 5

Acute radiation sickness dose

Answer 5

2-10 Sv to the whole body

Symptoms begin within a few hours.

Exposed to > 10 Sv to the whole body = death within 24 hours.

Question 6

Chronic radiation sickness

Answer 6

Hair loss, cataracts, sterility, obliterative endarteritis.

Question 7

Who can be damaged by non-deterministic effects of radiation?

Answer 7

Damage to patient and also future children (for male and female patients) = therefore somatic AND genetic.

Question 8

Factors affecting dose of radiation

Answer 8

1. Type of radiation - only interested in x-rays
2. Tissues being irradiated
3. Age of the patient

Question 9

Dose limits per annum for: Classified worker, non-classified worker and general public.

Answer 9

Question 10

The national radiological protection board estimate that the main dose for dental workers should be _____________.

Answer 10

<0.1mSv (never exceed 1mSv)

Question 11

ALARP

Answer 11

As
Low
As
Reasonably
Practicable

Question 12

How dangerous is a periapical radiograph in comparison to smoking?

Answer 12

1 in 200 people will die from smoking, compared with 1 in 5 million people dying from periapical.

Question 13

What are two changes to the X-ray which can be made to reduce developing fatal malignancy?

Answer 13

Change from D speed to F speed (highest film possible), change collimator from round to rectangular.

Question 14

Patients age - 10-20 multiplication factor for risk

Answer 14

2 times

Question 15

Patients age - <10 multiplication factor for risk

Answer 15

3 times

Question 16

Where does most of a person radiation dose come from?

Answer 16

84% from foods etc (bananas, avocado).

Average daily exposure 100 BED.

(15% from medicine and dentistry)

Question 17

Ways to reduce dose

Answer 17

1. Avoid taking unnecessary radiographs
2. Film speed - use F speed
3. kV of machine - higher = lower dose
4. Rectangular collimator vs round

Question 18

The intensity of a beam

Answer 18

The number of ‘photons’ in a beam at a specific place.

Therefore the further away you are from the source of radiation the less likely we are to be exposed to many x-ray photons.

Question 19

Controlled area

Answer 19

Is the area around the patient and the X-ray tube where only the patient should be present, the rest of the controlled area should be a “no go zone”.

Question 20

Controlled area size for an x-ray operating at <70kV

Answer 20

controlled area = 1.5m in diameter (this can change depending on the local rules)

Question 21

In DDH, how far away from x-ray are you required to stand?

Answer 21

2m or behind appropriate shielding (led etc)