# QA/QC dose reduction strategies Flashcards

1
Q

what percentage does CT contribute to dose

A

Comprise only 17% of all radiological examinations, but…

Contribute to 49% of all the effective dose of all radiological examinations

2
Q

What is absorbed dose?

A

total energy imparted on the human body (absorbed by tissues)

3
Q

what is equivalent dose

A

assesses how much biological damage is expected from absorbed dose: takes type of radiation into account and address this impact

4
Q

what is effective dose

A

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

5
Q

A
• 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
6
Q

A
• 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
7
Q

What are the three main dose metrics in CT

A

CT dose index

Dose length product

Effective dose

8
Q

What doesn’t slice sensitive profile take into account

A

scatter radiation outside of the slice

9
Q

What is dose length product

A

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

10
Q

does pitch affect dose? If so, how?

A

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
11
Q

Does MSCT affect dose? Explain how whether yes or no

A

yes
-Wider collimator settings to avoid penumbral effects are called ‘overbeaming’

-Result in radiation outside of the detectors hence increase dose

12
Q

What does QA mean

A

Maintaining a desired level of quality in a service or product

13
Q

What does QC mean

A

A system of maintaining standards in manufactured products by testing a sample of the output against the specification

14
Q

What does DRL reporting do?

A

Promotes awareness

Promotes education

Can highlight protocols that require adjustment

Action can be immediate

Reduces doses

Encourages collaboration

Assists in compliance

15
Q

Dose reduction strategies involved in QA/QC

A
• not to do the scan
16
Q

what are technical dose reduction strategies

A

ATCM

Adapts tube current to account for different attenuations

17
Q

what factors affect ATCM (age/ where pt must be positioned)

A
• used with caution for small patients i.e. children
• bariatric patients may cause issues
• pts must be positioned within isocentre
• arms must not be within FOV (will increase dose)
• modulation software may be innacurate with metal prosthesis