Justification and optimisation in radiation protection : which one is first ?

Justification and optimisation in radiation protection : which one is first ? Michel Bourguignon, MD, PhD Professor of Biophysics, Faculty of medicine of Paris Deputy Director General, ASN, France michel.bourguignon@asn.minefi.gouv.fr www.asn.gouv.fr 10th European ALARA Network Workshop Prague - 13 September 2006

Basic principles of RP ICRP 26, 1977 Justification of exposures Optimisation of exposures Limitation of doses of workers and population

Basic principles of RP Suppression of unjustified nuclear activities, and optimization and limitation of doseshave had positive effects: Suppression of deterministic effects Minimisation of the occurrence of stochastic effects

Basic principles of RP Justification Optimization Limitation Citation in this sequential order

Basic principles of RP Exposures are justified • Citation in the sequential order: • Justification • Optimization • Limitation

Basic principles of RP Exposures are justified Justified exposures are 2. optimized • Citation in this sequential order : • Justification • Optimization • Limitation

Basic principles of RP Exposures are justified Justified exposures are 2. optimized During the nuclear activity 3. doses are limited • Citation in this sequential order : • Justification • Optimization • Limitation

Basic principles of RP The sequence 1/justification, 2/optimization, 3/limitation seems very logicbut it happens that nuclear activities are justified because they are optimized. We may not have paid enough attention to the process of justification and optimisation. Which one is first ?

Justification (1) ICRP recommends that when « nuclear activities » are being considered, the radiation detriment should be explicitly included in the process of choice. Consequently, all detriments and costs of practice are being considered and the justification of a practice goes far beyond the scope of radiation protection.

Justification (2) NEA/OECD says that justification of « nuclear activities » involves social, economical and political issues in addition to radiation protection. Consequently, any « nuclear activity » should produce a net benefit, involving many value judgement, difficult, if not impossible, to quantify.

Justification (3) Justification is a difficult concept and its application to a particular « nuclear activity » is rarely discussed. Nuclear weapons were developped in the context that national security justified the risks of the enterprise. Many « nuclear activity » were justified well before the justification principle was set up by ICRP

Optimization Exposures to radiation should be as low as reasonably achievable. Thus, optimization implies that measures are taken to reduce exposures until the benefits of further reduction do not justify their cost. In practice, use of the best technology, and mandatory dose reduction if practicable at reasonable cost.

RP philosophy ! Since justification means that no « nuclear activity » should be adopted unless it produces enough benefit to offset the radiation detriment it causes, it appears that below a treshold of radiation detriment, i.e., when the « nuclear activity » is optimized, it may be adopted. Does this mean that only optimized « nuclear activities » can be justified ?

Examples Radioscopy Coronaro-scanography Whole body CT Virtual colonoscopy Chest X ray for medico-legal purpose Controls at frontiers Radon exposure

Radioscopy (1) Early 20th century, a new efficient and promising technique Use of radioscopy during World War I: no question of justification (saving of lives) Development of radioscopy for lung and bone examination for tuberculosis : no question of justification

Radioscopy (2) Use of radioscopy without protection: leukemias of radiologists from 1920s till 1950s 1928 International X ray and radium protection committee (future ICRP) Progress : X ray image intensifiers (1950s), image intensifiers/TV cameras (1960s), CCD cameras, digital image processing and enhancement

Radioscopy (3) Development of cardiologic and vascular applications in combination with catheterization guided radioscopy Recent formal interdiction of radioscopy without image intensification with Euratom Directive

Radioscopy (4) A century of radioscopy, great and useful technique for injuries and tuberculosis Not justified anymore because not optimized Finally forbidden because of a lack of optimization and replacement by an optimized technique.

Coronaro-scanography (1) Development of coronaro-scanography as a combination of spiral CT and multislice detectors Justification a priori because coronary artery disease has a high prevalence and coronaro-scanography is a non invasive technique CT investment economically rewarding

Coronaro-scanography (2) PDL = 2000 Gy.cm (much greater than PDL of ordinary chest CT) Equivalent dose ≈ 80 mGy Slices 0.6mm and resolution of 1.2mm (Shannon theorem) Request for a better resolution [<1mm] to detect smaller lesions, with a dosimetric cost

Coronaro-scanography (3) A series of questions What to do with a doubtful coronary-scanography examination ? A normal coronary angiogram ? Double dose ! What are the indications of CS ? What is the optimized procedure ? In France, coronary-scanography will be justified only if it is optimized

Other medical examples Whole body CT : not justified in France because not optimized for both medical and dosimetric reasons Virtual colonoscopy : indications depending on the procedure adapted to the expected resolution = justification / optimization link

Medico-legal examples Chest X ray (1) Established long ago as a regulatory tool for the diagnosis of tuberculosis Still used in France for getting an appointment and changing of appointment in the administration, for workers annually, for prisoners at each move of jail, for young sportman,… Also performed with transportable (outdated) equipments in trucks…

Medico-legal examples Chest X ray (2) New paradigm: only optimized chest X ray should be performed on good quality equipments only if the clinical situation justifies the practice To suppress all the not justified (because not optimized) examinations, ASN asks : Why are they performed ?

Medico-legal examples Controls at frontiers For drug search, antiterrorism measure, search of undercover entrance in countries… X ray techniques used because of their convenience Are these examinations justified ? Are they justified if optimized ?

Exposures to NORM For years, not in the scope of radiation protection because no possibility of prevention : justification was not even a question First exposure to ionizing radiations. Radon is the second cause of lung cancer Optimization of radon exposure by ventilation or special design of housing paves the way to their justification

Conclusion Justification and optimization are clearly linked with no clear and simple priority of one on the other one Need for a holistic approach in radiation protection Time has come to revisit all nuclear activities and to investigate their justification in the light of their optimization and vice-versa

Justification and optimisation in radiation protection : which one is first ?