Radiation dose, safety, and patient imaging with X-ray and CT (part 1) Flashcards
What is the International Commission on Radiological Protection (ICRP)?
An independent registered charity, with the mission to protect people, animals and the environment from the harmfull effects of ionising radiation. Its recommendations form the basis of radiological protection policy, regulations, guidelines and practice worldwide.
What are the basic principles of radiation protection?
- Justification
- Prevent deterministic effects (e.g. prevent exposure to critical organs such as the eye or skin.
- Minimize stochastic effects (= effects which occur when a person receives a high dose of radiation).
- Optimize radiation use (as low as reasonably achievable)
What is the relation between risk perception and radiation?
Radiation risk is often estimated to be too high by the ‘public’. This is due to:
- history (destruction)
- knowledge (complex)
- Control/trust
- Effects (not directly visible)
- Media (emphasise fear)
What are the deterministic and stochastic effects of radiation?
- Deterministic effects → energy transfer damages cells (first tissue effects are hair loss, eruthema, stare) → effects thus directly related to the absorbed radiation dose and the severity of the effect increases as the dose increases.
- Stochastic effects → energy transfer damages DNA → the chance effect of radiation, where if the dose increases the probability of the associated effect also increases (severity of the effect is independent of the dose) → statistical chance of malignity and genetic damage.
What is the definition of dosimetry?
Measurement of radiation exposure from x-rays, gamma rays, or other types of radiation used in the treatment or detection of diseases, such as cancer. Radiation exposure includes to what dose you are exposed to and what part of this dose is absorped.
How is the dose for radiation protection determined?
By measuring/calculating the:
- equivalent dose → dose quantity H representing the stochastic health effects of low levels of ionizing radiation → calculated for individual organs, based on the absorbed dose to an organ, adjusted to account for the effectiveness of the type of radation.
- effective dose → It is the tissue-weighted sum of the equivalent doses in all specified tissues and organs of the human body and represents the stochastic health risk to the whole body, which is the probability of cancer induction and genetic effects, of low levels of ionizing radiation.
What is the radiation weighting factor?
A dimensionless constant that accounts for the relative biological effectiveness of various types of ionizing radiation
Describe what unit is used to measure the organ dose, the equivalent dose and the effective dose.
- Organ dose → expressed in Gray (Gy)
- Equivalent dose → expressed in Sievert (Sv)
- Effective dose → expressed in Sievert (Sv)
Describe in broad terms how the organ dose and equivalent dose are calculated.
- Organ dose → absorbed energy per unit of mass
- Equivalent dose → dependent on organ dose and radiation weighting factor
Just study
What is the meant by the source scatter field?
The scattered radiation as an effect of the production of radiation waves.
Name factors that influence the scatter radiation where e.g. a nurse can be exposed to.
- Total time radiation usage / number of images
- Projection
- Distances
- Patient
- Parameters X-ray equipment
How can the X-ray dose be reduced?
- Collimated beam → parallel rays with minimal spread
- Reduce exposure time / number of images
- Beam quality
- Distance
- Geometry
What can e.g. nurses do for personal protection?
- Lead apron
- Radiation collar
- Radiation shielding
- Lead glasses
