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Interpretation of measured dose data in X-ray imaging

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 paula.toroi@stuk.fi. 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

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  1. 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 paula.toroi@stuk.fi Paula Toroi

  2. 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

  3. 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

  4. 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

  5. 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

  6. Beam properties: radiation quality 130% Paula Toroi Monte Carlo simulations are made with PCXMC (STUK, Finland)

  7. Patient properties Paula Toroi Monte Carlo simulations are made with ImpactMC (CT-imaging, Germany)

  8. 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

  9. 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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