Practical Radiation Protection Flashcards
What law does radiation follow?
The inverse square law
What are the 3 ways to reduce radiation exposure?
Limit time
Increase distance
Use shielding
What are the 2 types of fluoroscopy?
Fluoroscopy
Acquisition
How can we limit time to reduce radiation exposure?
(6)
If using fluoroscopy, limit exposure time (fluoroscopy uses moving x-rays)
Use pulsed exposure if possible
Reduce the pulse rate in fluoroscopy if lots of movement
If in nuclear medicine, spend less time around patients
If in nuclear medicine, patients have a yellow note to identify them
If you can leave the area, then leave it
What does last image hold mean in fluoroscopy?
The image is present even if the radiation isn’t being exposed to the patient anymore
If we double the distance from the source of radiation to us, what happens to the area over which the radiation is spread?
The area increases by a factor of 4
How does increasing the distance reduce radiation exposure?
(2)
The Rutherford we are from the source of radiation, the better
The effect increases as you increase the distance from the source
What are rules to follow in fluoroscopy?
(3)
Position the x-ray tube as far from the patient as possible
The x-ray tube must not be less than 30cm from the patient’s skin
Position the detector as close as possible to the patient, otherwise a higher dose of radiation will be received by the patient to get the same image
What is the half value layer of a material?
The thickness (amount) of a material that’s needed to reduce the dose by half
What does it mean if the half value layer of a material is thicker?
The material is less effective at reducing radiation
Do softer photons have more or less energy?
Less energy
Do harder photons have more or less energy?
More energy
Are softer photons more or less penetrating?
Less penetrating
Are harder photons more or less penetrating?
More penetrating
What’s the link between soft and hard photons and the penetration?
Th harder the photons are, the more penetrating they are
How much lead is added to shield us from radiation?
0.05mm
How does adding 0.05mm of lead shield us from radiation?
(2)
It reduces the number of photons, so the intensity in the beam decreases and the energy increases in the beam.
The softer lower energy photons are removed, so the beam contains harder and higher energy photons (beam hardening)
What is beam hardening?
When we remove the softer lower energy photons, causing the beam to move up to the harder end of the photon spectrum
When does lead ted to be used for shielding?
At lower energies
Why is a high atomic number used for shielding at lower energies?
Because it’s more attenuating for the photoelectric effect
What is used for shielding at lower energies?
(2)
Lead
High atomic number
What is used for shielding at higher energies?
Concrete
Why is concrete used for shielding at high energies?
Because it has a high density, which is more attenuating for the Compton effect
How does the half value layer work?
(4)
Low energy photons are removed when the material is present for the 1st half value layer
Now there’s only high energy photons so it’s harder to stop them. So the material needs to be thicker to stop it.
This keeps happening and the material keeps getting thicker
So the 2nd half value layer is more than the 1st half value layer
Where is most of the scatter located around the x-ray tube?
It’s located towards the x-ray tube
Why are the x-ray tubes under patients in fluoroscopy?
Because the scatter is towards the x-ray tube
Since we know that the scatter is towards the x-ray tube in fluoroscopy, how can we protect ourselves from scatter?
Stand on the opposite side of the patient, away from the source
What should we do if out hands end up in the primary beam during fluoroscopy?
It needs to be reported, so that the practice can be improved
When can our hand only end up in the primary beam?
During safeguarding cases
What does PPE stand for?
Personal
Protective
Equipment
How much lead does PPE have?
0.2mm
When is PPE mainly used?
In fluoroscopy
When do we wear PPE?
As a last resort- to keep us safe
What is the primary beam?
(2)
The x-ray between the detector and x-ray
Or
The x-ray between the patient and x-ray
Will PPE protect us from the primary beam?
No
Which is lower intensity- scatter or the primary beam?
Scatter
When professionals, e.g. surgeons, have to put their hands in the primary beam, what is worn?
Lead gloves
What is the issue with wearing lead gloves when needing to put hands in the primary beam?
The lead gloves cover the detector, so not all the x-rays are detected. So the detector increases the dose of radiation, causing more scatter and increasing the dose of radiation to the patient
What is the most protective PPE equipment?
Why?
Ceiling mounted screens in fluoroscopy areas
Because they have 0.5mm of lead, but sometimes 2mm of lead
Why have lead glasses been introduced?
Because radiologists began getting cataracts
What does a thyroid shield do to the radiation?
It halves the dose of radiation
When are rad pads used?
In cardiac cathatar
What happens if we don’t position the rad pads properly?
The dose of radiation will increase for us and the patients
What do rad pads do?
They protect the operator from scatter
What should we do with ceiling mounted screens?
(4)
Use wherever possible
Challenge the clinician that we should use it
Place it as close to the individual to shield them as much as possible
If they’re multiple people and there’s not other ways of shielding them, the playing the screen closer to the patient may provide a larger shadow and protect them too. But it’ll be less effective for the operator
What are the features of dosimeters?
(3)
They’re a form of PPE
They won’t protect us from the radiation- they only measure the amount of radiation that we’re exposed to
They’re treated as PPE, so we have a legal duty to use them and take care of them
What parts of the body do dosimeters measure?
(3)
Whole body
Skin
Lens of eye
What are the 2 types of dosimeters?
TL
OSL
How do TL dosimeters work?
They emit light when heated
How do OSL dosimeters work?
They emit light when stimulated by lasers
What are the features of OSL dosimeters?
(3)
They’re small devices
They can be worn on fingers
They’re reusable
What’s an example of digital readout dosemeters?
EPDs
What are the features of digital readout dosemeters (EPDs)?
(3)
They read what your radiation dose is right now
They measure very low doses
They read background radiation too
How should we wear dosimeters correctly?
(5)
Must be worn within the holder
Worn when in radiation areas
Label showing wearers name visible
Between hip and shoulder
Don’t wear it where it could be obscured (seen) by metal
How should we store dosimeters correctly?
(5)
Keep away from hot pipes or radiators
Protect from chemical attack
Don’t store near luminous articles
Don’t pierce, bend or damage
Don’t take onto an aeroplane
Where are dosimeters worn?
(3)
Collar- worn above PPE
Chest- worn below PPE
Waist- worn below PPE
When should radiation safety be notified regarding dosimeters?
(5)
A dosimeter is lost
Doses are above investigation levels
A dosimeter is suspected to be damaged
If it’s dropped in a radiation area
If a staff member is involved in a radiation incident while wearing it
Why does it benefit us to reduce the patient’s exposure?
Because the scatter we receive is related to the patient’s dose
