Dosimetry Flashcards
Two types of damage caused by ionising radiation
Direct DNA damage
Indirect damage via free radicals
Two historical radiation incidents
Chernobyl
Hiroshima
What is dosimetry?
The quantification of radiation absorbed by human tissue
Why is dosimetry important?
It assesses risk, informs ALARA, and optimises dose monitoring
What is absorbed dose, and its SI unit?
The energy absorbed per unit mass of tissue, measured in Gray (Gy)
What is a Dose Area Product (DAP) meter?
A device measuring absorbed dose multiplied by the irradiated area
Two advantages of measuring absorbed dose
Quick results
Standardisation for dose optimisation
Two disadvantages of measuring absorbed dose
It doesn’t account for tissue radiosensitivity or different radiation types
What is equivalent dose?
Absorbed dose multiplied by a radiation weighting factor, measured in Sieverts (Sv)
What is the weighting factor for X-rays?
1
How is effective dose calculated?
By multiplying an organ’s equivalent dose by its tissue weighting factor, summing for all exposed organs
Why is effective dose important?
It accounts for radiation type, output, and tissue sensitivity
What is the effective dose of a CT head scan compared to natural background radiation?
Equivalent to 1 year of background radiation.
What is the additional lifetime cancer risk of a CT abdomen/pelvis scan?
1 in 2000
What are the 5 steps to managing ionising radiation risk?
Identify hazards
Assess likelihood
Evaluate severity
Manage exposure
Optimise safety measures
Name two risk management strategies in dosimetry
Shielding and dose optimisation
What is accidental radiation exposure?
Exposure received in error when no radiation was intended
What is unintended radiation exposure?
Intended exposure significantly greater than planned
Why is explaining radiation risk important in consent?
It helps patients understand the relative risks and benefits, especially in the context of misinformation
What role does dosimetry play in consent?
It provides clear metrics to explain and justify risks
What are the three main types of radiation doses?
Absorbed dose (Gy)
Equivalent dose (Sv)
Effective dose (Sv).
What principle guides minimising radiation exposure?
ALARA (As Low As Reasonably Achievable).
