QA/QC dose reduction strategies Flashcards
what percentage does CT contribute to dose
Comprise only 17% of all radiological examinations, but…
Contribute to 49% of all the effective dose of all radiological examinations
What is absorbed dose?
total energy imparted on the human body (absorbed by tissues)
what is equivalent dose
assesses how much biological damage is expected from absorbed dose: takes type of radiation into account and address this impact
what is effective dose
used to assess potential for long term effects that may occur
takes into account of absorbed dose of all organs, relative harm level and sensitivities of tissue
list 4 stochastic radiation bioeffects
- Probability
- Probability of harm increases with dose
- No threshold
- There is no risk free dose
- All doses have potential to cause biological risk
- May take years to become apparent
- Can be hereditary
List 4 deterministic radiation bioeffects
- severity
- Increases with increasing dose
- There is a threshold, below which there is no effect
- Threshold doses are relatively high
- Can cause cell damage and death above this level
- Referred to as ‘early effects’’
- Can include erythema, epilation etc.
- Cumulative
What are the three main dose metrics in CT
CT dose index
Dose length product
Effective dose
What doesn’t slice sensitive profile take into account
scatter radiation outside of the slice
What is dose length product
Total dose across the length of the scan
A calculated value from known factors, kVp, mA, SFOV, etc and the length of the scan series
does pitch affect dose? If so, how?
Yes
- Pitch of 1.0 has dose approximately equal to an axial scan
- Pitch of 0.75 (over lapping or Z over scanning) has 33% more dose
- Pitch of 1.5 has 66% less dose
Does MSCT affect dose? Explain how whether yes or no
yes
-Wider collimator settings to avoid penumbral effects are called ‘overbeaming’
-Result in radiation outside of the detectors hence increase dose
What does QA mean
Maintaining a desired level of quality in a service or product
What does QC mean
A system of maintaining standards in manufactured products by testing a sample of the output against the specification
What does DRL reporting do?
Promotes awareness
Promotes education
Can highlight protocols that require adjustment
Action can be immediate
Reduces doses
Ensures ALARA is adhered to
Encourages collaboration
Assists in compliance
Dose reduction strategies involved in QA/QC
- not to do the scan
justified by radiologist
optimised by radiographer
