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Interpretation of measured dose data in X-ray imaging. IRPA 14.-18.5.2012 Glasgow, UK. Paula Toroi PhD, Senior scientist STUK-Radiation and Nuclear Safety Authority, Finland [email protected] Quantities. Measurable quantity Air kerma based technical parameter Not a patient dose

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interpretation of measured dose data in x ray imaging

Interpretation of measured dose data in X-ray imaging

IRPA14.-18.5.2012

Glasgow, UK

Paula Toroi

PhD, Senior scientist

STUK-Radiation and Nuclear Safety Authority, Finland

[email protected]

Paula Toroi

quantities
Quantities
  • Measurable quantity
    • Air kerma based technical parameter
    • Not a patient dose
  • Organ or tissue dose
    • A base for risk estimates (ICRP 103, 2007)

Effective dose

  • Generally known and used quantity
  • One simple combined risk quantity
  • Not for individuals

Statisticalriskmodels

  • For selected organs
  • BEIR VII, 2006

Paula Toroi

methods for patient dose estimation
Methods for patient dose estimation
  • Use of tabulated doses
    • Averaged values for some clinical practice
    • E.g. Effective dose = 0.02 mSv (thorax)
    • Uncertainty for general use is high
  • Conversion from measured value

Organ dose or effective dose=

Measurable quantity* Conversion factor

    • E.g. Conversion factor = 0.25 mSv/mGy (thorax)
    • What is the uncertainty of a conversion?

Paula Toroi

influence parameters for conversion
Influence parameters for conversion

Beam properties:

  • Beam geometry
    • Size, shape, location
  • Radiation quality
    • Radiation spectrum

(tube voltage, filtration)

Patient properties:

  • Body: size, shape, anatomy
  • Organ: size, shape, location

Paula Toroi

tabulated conversion factors
Tabulated conversion factors

Beam properties:

  • for specified examination
  • some times for different radiation qualities

Patient properties:

  • normally for standard size patient model

EC, 2008 RP N° 154

Paula Toroi

beam properties radiation quality
Beam properties: radiation quality

130%

Paula Toroi

Monte Carlo simulations are made with PCXMC (STUK, Finland)

patient properties
Patient properties

Paula Toroi

Monte Carlo simulations are made with ImpactMC (CT-imaging, Germany)

main uncertainties in the conversion
Main uncertainties in the conversion
  • Radiation quality (RQ)
    • It is very important to choose a correct factor
  • Patient properties
    • Large differences between individuals
    • Correction factors available for CT

(AAPM 204, 2011)

What is the uncertainty of risk estimation?

Paula Toroi

slide9

Thank you!

Acknowledgements:

*IAEA collaborative research project E2.10.008. The development of advanced dosimetry techniques for diagnostic and interventional radiology.

*Colleagues from STUK: Anna Kelaranta, Markku Tapiovaara, Teemu Siiskonen and Antti Kosunen

Paula Toroi

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