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The Concept of Reference Dose Values in the European Union

The Concept of Reference Dose Values in the European Union. Compiled for the CT Stakeholders‘ meeting hosted by MITA at RSNA 2009 by Stefan Ulzheimer, PhD Siemens Healthcare Director Global Collaborations CT Siemens Medical Solutions U.S.A., Inc. Basis for Reference Dose Values in the EU.

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The Concept of Reference Dose Values in the European Union

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  1. The Concept of Reference Dose Values in the European Union • Compiled for the CT Stakeholders‘ meeting hosted by MITA • at RSNA 2009 by • Stefan Ulzheimer, PhD • Siemens Healthcare • Director Global Collaborations CT • Siemens Medical Solutions U.S.A., Inc.

  2. Basis for Reference Dose Values in the EU • Typically, no maximum limits for the medical use of ionizing radiation do exist because in most legal systems the physician is free to chose the methods for diagnoses and treatment. • Therefore, for medical use the International Commission on Radiological Protection (ICRP) emphasizes the importance of two principles [1] • Justification of the medical use of radiation • Optimization of the use of radiation taking into account the protection effort and the achievable dose reduction These two principles reflect the only commonly accepted principle for the use of ionizing radiation in medicine, ALARA (As Low As Reasonably Achievable) [1] ICRP Publication 73: Radiological Protection and Safety in Medicine. International Commission on Radiological Protection. October 1. 1996. Elsevier

  3. Justification and Optimization Justification • All examinations with ionizing radiation need to be justified both generally and individually. The benefit has to outweigh the potential risk. Optimization • The goal of the optimization is then to maximize the net benefit of the examination for the patient. The ICRP also notes that in the medical context upper dose limits are not a suitable tool for radiation protection. The ICRP recommends reference dose values (RDVs) to limit the exposure of patients to ionizing radiation.

  4. What is a “Reference Dose Value” • ICRP defines reference dose values as a measurable unit to identify situations in which the radiation exposure is unusually high. • Thus, reference dose values are thresholds above which one has to look for reasons why they are exceeded and one should look into measures to lower doses. • ICRP recommends the implementation of reference dose values • as easily measurable units, for • frequent diagnostic procedures, and for • generally available technology. • Reference dose values should be checked and updated periodically. • Processes should be implemented that are able to detect when reference dose values are consistently, significantly exceeded to check the diagnostic equipment and to verify if appropriate radiation protection procedures are implemented.

  5. Implementation in the European Union • The European Union (EU) acted on this ICRP recommendation and released in 1997 the “Medical Exposure Directive” (97/43/EURATOM). The member states of the European Union have to implement this directive into local law. • 97/43/EURATOM defines RDVs as • “Dose values for diagnostic medical procedures using ionizing radiation or – in the case of radio-pharmaceuticals - activities • for typical examinations • for groups of patients • using standard units or standard phantoms • for generally defined examinations and equipment. • These levels are expected not to be exceeded for standard procedures when good and normal practice regarding diagnostic and technical performance is applied.”

  6. Implementation in the Member Countries of the EU Examples of Reference Dose Values for different Members of the EU, the regulating bodies and year when they were published • Germany, Bundesamt für Strahlenschutz (BfS), July 12, 2003 • Switzerland, Bundesamt fuer Gesundheit (BAG), October 26, 2007 • France, Societe Francaise de Radiologie (SFR), 2004 • UK Department of Health, Ionizing Radiation Regulations, 2000 • Norway, Norwegian Radiation Protection Authority (NRPA), 2007 Reference dose values are different in each country, e.g. * For comparison ** Pass/Fail criteria

  7. Implementation in Germany • The principles of 97/43/EURATOM were implemented in in Germany law in the Radiation Protection Ordinance (Strahlenschutzverordnung, StrlSchV) and the X-ray Ordinance (Röntgenverordnung, RöV) in 2001 and 2002 respectively. • StrlSchV also defines RDVs as “recommended dose values or activity values for the medical use of radio-pharmaceuticals for typical examinations obtained in standard phantoms or patient groups with standard units for individual equipment categories.“ • § 81/2 StrlSchV states that “the examination of humans has to be based on diagnostic reference dose values. If diagnostic reference dose values are exceeded this has to be justified in writing. The Federal Office for Radiation Protection (“Bundesamt für Strahlenschutz”) compiles and publishes reference dose values“. • It is incumbent on the users to comply with these regulations. • Reference dose values have to be applied in standard procedures and standard patients (Typically 70 kg, 170 cm). • The German states have to implement local quality assurance groups “Ärztliche Stellen” who are tasked to check if the regulations in the law are obeyed. • Typically the responsible state office (State Ministry of Public Health) assigns this responsibilty to the Chamber of Physicians “Landesärztekammer” in the respective German states.

  8. Tasks of the Quality Assurance Groups (“Ärztliche Stellen”) • The tasks of the Quality Assurance Groups in the German States are regulated in the directive “Ziele und Anforderungen an die ärztlichen und zahnärztlichen Stellen“. • The quality assurance groups have to report any continued, unjustified exceeding of reference dose values to the responsible state office. • The state office then can task an inspector to check the cause for this on site or perform the check itself and recommend counteractive measures to reduce radiation exposure.

  9. Reference Dose Values - Existing Reference Dose Values Reference dose values as published by the Federal Office for Radiation Protection (“Bundesamt für Strahlenschutz”). Tables are published for the following groups of examinations: • Radiography in Adults • Fluoroscopy in Adults • CT Exams in Adults • Radiography in Children (10 months, 2 years and 10 years old) • Frequent nuclear exams, e.g • bone, thyroid and kidney scintigraphy • heart, lung and brain perfusion • lung ventilation • PET, glucose uptake • Ratio of applied activity based on weight for peds (3 – 70 kg in steps of 2 kg)

  10. Reference Dose Values - Example 1, Radiography in Adults * ap: anterior-posterior pa: posterior-anterior ** lat: lateral *** cc: cranio-caudal mlo: medio-lateral-oblique

  11. Reference Dose Values - Example 2, Computed Tomography * CTDIw : weighted CT dose index ** Main indication sinusitis. For fractures higher dose values might be necessary. *** Intervetrebral disk diagnosis

  12. How were the Reference Dose Values obtained? • The reference dose values for CT are mainly derived from surveys in 1999 across Germany taking into account previously published values. • The surveys were carried out by the German X-ray Society (“Deutsche Röntgengesellschaft e.V.”) and the German Electrical and Electronic Manufacturers' Association (“ZVEI - Zentralverband Elektrotechnik- und Elektronikindustrie e.V.”), two non-profit organizations. • The published values are mainly based on the 75th percentile of the dose values obtained from these surveys. • The directive states that the target doses for users of modern equipment should rather be the 25th percentile of the published data [2] to take into account technical innovation because at the time of the survey over 50% of the scanners were already older than 4 years. [2] M. Galanski, H.D. Nagel, G. Stamm: CT-Expositionspraxis in der Bundesrepublik Deutschland, Ergebnisse einer bundesweiten Umfrage im Jahre 1999. Fortschr. Röntgenstr. 173 (2001), R1-R66.

  13. Summary • The concept of reference dose values is a powerful tool to decrease average dose exposure to the population and create dose awareness. • More important than the reference dose values itself is a properly implemented process that forces the physicians to consciously chose the dose levels they prescribe and document when they choose to exceed the reference dose value. • Reference dose values should NOT be upper limits for radiological examinations. The required dose for a specific exam does not only depend on technical parameters and the application but also on many other individual factors such as patient size and weight, how cooperative the patient is, the experience of the involved personnel, etc. • The decisive parameter is not if the reference dose value in an individual exam is exceeded if that can be explained and the physician has a justification to order higher dose. • The concept of reference dose values only works well in combination with well trained personnel who makes conscious and educated decisions when using ionizing radiation.

  14. Publications Country/Region Name Published International International Commission on Radiological Protection (ICRP) 1996 International Atomic Energy Agency (IAEA) Radiation protection of patients (RPoP) February 1996 International Commission on Radiation Education (ICRU) International Society of Radiology Europe European Guidelines on Quality Criteria for Computed Tomography, EUR 16262 May 1999 Germany Bundesamt für Strahlenschutz (BfS) July 12, 2003 Strahlenschutzkommission (SSK) July 12,2006 Switzerland Bundesamt fuer Gesundheit (BAG) October 2007 France Societe Francaise de Radiologie (SFR) 2004

  15. Publications Country/Region Name Published UK Department of Health, Ionising radiation (medical exposure) regulations 2000 Institue of Physics and Engineering in Medicine (IPEM) 2005 Health Protection Agency (HPA) 2003 NRPB joined the Health Protection Agency April 2005 Norway Norwegian Radiation Protection Authority (NRPA) 2007 USA The American Association of Physicists in Medicine (AAPM) March 2005 CT Accreditation Program Requirements, American College of Radiology (ACR) January 2008 Canada Canadian Association of Radiologists March 2002 Japan Japanese Association of Radiological Technologists (JART) 2002

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