Scattered Radiation Flashcards
What is scattered radiation?
Radiation that has been deflected by the body of the patient that flies in all directions.
Why is this a problem?
It can make an x-ray look indistinct and grey (as the image becomes over-exposed which reduces contrast) and represents a safety issue for animal handlers
How can scattered radiation be reduced?
Collimation
Lead rubber lining of table
Use of higher kVp exposures
What is collimation?
The use of lead ‘shutters’ to decrease the window of x-rays leaving the x-ray tube.
What is the principle of using a grid?
The grid is aligned with the primary beam of x-rays so the image is less affected by scatter. It doesn’t prevent scatter to the handlers
Define the gray and the sievert.
Gray - absorbed dose of radiation = joules/kg
Sievert - dose equivelent e.i. the effect of radiation = gray x quality factor. (more penetrating/less damaging radiation has a lower q.f)
What is the maximum permissible dose of radiation for:
a) a person at work who is >18
b) a member of the public?
a) 20mSv/yr
b) 1mSv/year
What are the two common types of radiation detector?
Film badge or a thermoluminescent detector.
How can doses of radiation be minimised?
Time - only use when neccessary and minimise retakes
Distance - inverse square rule, hold at arms length etc.
Use barriers
What are the rules concerning the ‘controlled area’?
2m away from x-ray tube or the whole x-ray room. Must have signs
What is the controlled area?
The area around the primary beam where the average radiation dose exceeds the permissible limit.
What is an RPA?
Radiation Protection Advisor - Someone from outside the practice who advises on local rules for radiographic practice and will inspect facilities.
What is an RPS?
Radiation Protection Supervisor - in situ supervisor. Notifies use of radiation to HSE, administers local rules and keeps track of dosimeter readings
