Radiation Safety Flashcards
Who was the first person to discover that radiation exposure had had adverse affects on the skin?
Dr Edmund Kells
What are the 2 types of biological effects of radiation?
- Deterministic (non-stochastic) - those we know will occur
2. Non-deterministic (stochastic) - those which may occur
When looking at DETERMINISTIC effects;
What happens with the biological effects below and above the threshold dose?
In deterministic effects;
Below threshold - the biological effects do NOT occur.
Above threshold - the biological effects DO occur.
Who can be damaged by deterministic effects?
In relation to the person affected, what are these effects known as?
All the damage effects the person exposed to the radiation.
It effects their body and therefore they are known as somatic effects.
Can somatic effects be positive and if so why?
Yes they can be positive.
This means you can determine the threshold dose and expose a patient to a specific dose of radiation for treatment (eg. kill of cancer cells that give rise to tumours)
Can deterministic effects be adverse?
Yes they can also be adverse
What are the two grades of biological deterministic effects of ionising radiation?
- Acute
2. Chronic
Give 2 examples of ACUTE deterministic effects of ionising radiation?
- Radiation sickness - If they receive 2-10 Sv whole body irradiation.
- Death - If they receive >10 Sv whole body irradiation
Give 4 examples of CHRONIC deterministic effects of ionising radiation?
- Hair loss
- Cataracts
- Sterility
- Obliterative endarteritis
When do deterministic effects occur?
They occur at random - chance or probability.
Is there a threshold dose associated with non-deterministic effects of ionising radiation?
No, there is no threshold dose.
Who can be damaged by non-deterministic effects of ionising radiation?
In relation to those affected, what are these 2 types of effects known as?
Can damage both the patient exposed to radiation and future children
These effects are known as somatic and genetic effects.
With non-deterministic effects;
Is the amount of damage related to the radiation dose?
No.
Although, there is less chance of damage if exposed to a low dose of radiation over a high dose.
With non-deterministic effects;
What do somatic effects often give rise to?
They often give rise to the development of malignancy
With non-deterministic effects;
What do genetic effects often give rise to?
Can give congenital abnormality which may include malignancy.
However, for these effects to occur the reproductive organs of either male or female would have to be exposed to radiation.
Out of deterministic and non-deterministic effects; which effects are most likely to occur in dentistry?
Non-deterministic effects
This can be problematic.
Why do non-deterministic effects occur more often than deterministic effects in dentistry?
As exposure is not sufficient enough for the radiation to reach a threshold dose that would cause deterministic effects.
List 3 factors that affect radiation dose?
- Type of radiation – we are interested only in x-rays
- Tissues being irradiated
- Age of the patient
Based on SEDENTEXCT, what is the typical effective dose for bitewings/periapicals ?
0.0003 – 0.022 mSv
What is the typical effective dose for DPT ?
0.0027 – 0.038 mSv
What is the typical effective dose for a maxillary occlusal ?
0.008 mSv
What is the typical effective dose for a Lateral Cephalometric ?
0.0022 – 0.0056 mSv
What is the typical effective dose for a PA skull ?
0.02 mSv
What is the typical effective dose for a lateral skull?
0.016 mSv
What is the typical effective dose for a Chest PA ?
0.014 mSv
What is the typical effective dose for a dento-alveolar CBCT ?
0.01 – 0.67 mSv
What is the typical effective dose for a craniofacial CBCT ?
0.03 – 1.1 mSv
What is the typical effective dose for a CT mandible & maxilla ?
0.25 – 1.4 mSv
Who does the dose limitation apply to ?
Applies to workers.
What is the mean dose limit for dental workers ?
<0.1mSv
What dose is recommended that should never exceed?
1mSv (dose limit for the public)
What is the dose limits for patients?
There are no set dose limits for patients.
- Although there are no limits, you must keep in mind the ALARP principle
When should patients be exposed to radiation?
Only if it is clinically necessary, in order to diagnose and treatment plan their problems
What does ALARP stand for?
As Low As Reasonably Practicable
What is the chance of dying from a periapical?
1:5,000,000
What is the chance of dying from a DPT?
1:1,000,000
Does age of the patient affect their risk of developing adverse affects from radiation?
Yes,
The younger the patient is = the GREATER the risk of developing adverse affects from radiation.
What are the 4 different sources of ionising radiation?
- Natural background incl. food 84%
- Fallout & radioactive waste <1%
- Medical & Dental 15%
- Occupational <1%
Which source emits the highest % of ionising radiation?
What is the % of radiation emitted by this source?
Natural background incl. food
84%
Which sources emit the lowest % of ionising radiation?
What is the % of radiation emitted by these sources?
- Fallout & radioactive waste
- Occupational
<1%
List 5 radioactive foods
Any 5 of these:
- Brazil nuts
- Butter beans
- Bananas
- Potatoes
- Carrots
- Red meat
- Avocado
- Beer
- Water
- Peanut butter
What is the banana equivalent dose (BED)?
1 banana is equivalent to 1% of the average daily exposure
What is the average daily exposure in BED?
100 BED
What is a chest CT scan in BED?
What is this value in mSv?
70,000 BED
7mSv
What must you consider before exposing a patient to radiation?
Consider:
The benefits of gaining the desired info in order to carry out diagnosis and treatment planning against
vs.
The potential harm of radiation dose to the patient (non-deterministic effects in dentistry which can occur at a low dose)
What is Justification in Radiology?
Justification is the process in which we must undertake under current legislation, every time before exposing a patient to ionising radiation.
List 3 ways that we can reduce dose?
Any 3 of these:
- Avoid unnecessary radiographs
- Use of Selection Criteria
- Film speed – use highest speed possible - preferably use F speed
- Digital radiography may help - similar to f speed
- kV of machine – higher the kV, lower the dose
- Rectangular collimation - much lower than round shaped beam
- Collimated DPT views - restricts radiation to areas of interest
- Regular servicing of machines
- Knowledge & Understanding!
What is beam intensity?
The number of “photons” in a beam at a specific place.
What is inverse square law?
What does this mean?
Where the intensity of radiation is proportional to 1/the distance squared.
This means the further we are away from the source of radiation, the less likely we are to be exposed to many x-ray photons.
What is the controlled area?
The area around the patient and the x ray tube, where only the patient should be present.
The rest of the controlled area is considered a ‘no go zone’.
What is the size of the controlled area if the X-ray machines are working <70kv?
1.5m in diameter
It also extends in the primary beam for as long as it would take for the intensity of radiation to be almost minimum.
What else is also important to have in your controlled area?
Protective barrier
Where must the radiation activation button be found?
The button must also be behind this barrier.
How far away should staff stand from all machines?
DDHstand 2m away for all machines
