International standards, relating to safety of diagnostic radiology equipment

 
Customers generally want to order any product on the international market only if they have an appropriate certainty that the product conforms to some pre-established demands. Such demands may relate e.g. to energy supply or serviceability of the product but above all to its safety and performance according to its intended use. It is the reason of developing of international standardization. The two greatest international standardization bodies are ISO (International Standardization Organization) and IEC (International Electrotechnical Commission). The latter deals with electric while the former with non-electric standardization. International standards for medical electrical equipment and within it for diagnostic radiology equipment are produced by IEC.

The International Electrotechnical Commission (IEC)

 
In 1904, delegates to the International Electrical Congress, being held in St. Louis, USA, adopted a report that included the following words: „...steps should be taken to secure the co-operation of the technical societies of the world, by appointment of a representative Commission to consider the question of the standardization of the nomenclature and ratings of electrical apparatus and machinery.”

As a result, IEC was officially founded in June 1906, in London, England, where its Central Office was set up by participation of twelve countries. Hungary is one of the founding members although at that time it was part of the Austrian-Hungarian Monarchy. By 1914 the IEC had formed four technical committees. By 1923 the number of technical committees had increased to 10, by 1980 to 80. At present IEC has about 110 Technical Committees (TCs). In 1948 the IEC Central Office moved from London to Geneva. Income of the IEC Central Office, which has about 50 employees, is only from purchasing standards and membership fees of the member states.

As experts participate in standardization on their own expenses (or that of their organization or organizations sponsoring the corresponding national committee), most of them are representatives of manufacturers.

Standardization relating to medical electrical equipment

 
In 1969 IEC created Technical Committee 62 for medical X-ray equipment, which committee some years later was enlarged to incorporate all medical electrical equipment. Now its name: Medical Electrical Equipment. The first meeting of TC 62 took place in Baden-Baden, Germany in 1969. Again Hungary was amongst the first members to take part in this committee: it joined in 1970, through Hungarian Standardization Office of that time. Medicor Works as manufacturer of medical X-ray equipment was interested in complying with IEC requirements, to be successful in the international market; therefore it paid for participation of its experts on meetings.

At present the TC 62 has four Sub-Committees (SCs):

SC 62A: Common Aspects of Electrical Equipment used in Medical Practice – this subcommittee elaborated the IEC 60601-1 „general standard” and it deals with general aspects of electricity in medical devices. Standard for electromagnetic compatibility (EMC) was also produced by this subcommittee.
SC 62B: Diagnostic Imaging Equipment (formerly X-Ray Equipment) – this subcommittee produces standards for diagnostic radiology, magnetic resonance and ultrasound equipment.
SC 62C: Equipment for Radiotherapy, Nuclear Medicine and Radiation Dosimetry.
SC 62D: Electromedical Equipment – its topic is all other types of medical electrical equipment.

TC 62 and its Sub-Committees have meetings usually every 18 months.
Hungary is member of TC 62 since 1970, through the Hungarian Standards Institution. It is an active (voting), so-called participating member (P-member) in TC 62, SC 62A and SC 62B. It is a so-called observer (O-member, having right to commenting but not voting) in SC 62C and SC 62D.

Working method of IEC

 
Members of IEC are the National Committees (NCs) of countries. In elaboration of standards each country may participate – if it is intended – by delegation of experts into the working groups, nominated to the Central Office (CO). Bodies participating in National Committees generally are: manufacturers, test houses, governmental bodies, professional societies, commercial agencies, representatives of users etc.

If – in national level – there is a demand for elaboration of a new standard or revision of an existing one, the NC may propose it to the IEC. Then the corresponding Technical Committee asks member NCs for voting, and in case of acceptance of the topic a new working group (WG) or maintenance team (MT) will be founded, with experts delegated by member NCs. Its necessary condition is delegation of experts at least from five member states. Groups (WGs or MTs) hold meeting, give homework to their members, and they may ask for opinion also by correspondence. Drafts of the planned standard are circulated by CO among member NCs for commenting and for voting several times in different stages (committee draft CD, committee draft for voting CDV, final draft international standard FDIS). Based on the comments the group revises the draft and it is circulated again. At the end if the FDIS (final draft international standard) is accepted by member NCs it will become international standard. (In the FDIS stage it isn’t done already to vote negatively.) This procedure lasts at least 14 months but often even 4 years. International standards express, as nearly as possible, an international consensus.

Comité Européen de Normalisation Electrotechnique (CENELEC)

 
CENELEC European electrotechnical organization was founded in 1973 by joining several organizations. Its Central Office is located in Brussels. Hungary became affiliated member of CENELEC in 1991 and became regular member in 2002, July 1st.

CENELEC TC 62 deals with medical electrical equipment in the European Union. Hungary is also an active member in this Technical Committee through the Hungarian Standards Institution. CENELEC TC 62 usually has meetings yearly, on which earlier Hungarian experts also took part. CENELEC TC 62 usually takes over the IEC TC 62 standards but in principle there is a possibility for modification. FDIS (Final Draft International Standards) issued for voting by IEC TC 62 are issued generally for parallel voting: for IEC TC 62 P-members and for CENELEC TC 62 members.

 

Participation of Hungary in the work of IEC TC 62 and CENELEC TC 62

 
Hungarian Standards Institution established its Technical Committee 843 to deal with IEC TC 62 and CENELEC TC 62 matters in 1995. TC 843 (as the Hungarian National Committee to IEC TC 62, SC 62A, SC 62B and to CENELEC TC 62) has meetings regularly, especially when IEC TC 62 / CENELEC TC 62 Standards are translated to Hungarian language. These standards have MSZ EN (Hungarian Standard - European Standard) heading.
Unfortunately, recently there is very little money for translation of standards so standards of these topics – as MSZ EN or sometimes MSZ IEC standards – are published in English but a so-called “cover” page which is of Hungarian language. Users of these standards in Hungary are few and they – according to their work – have to understand English.

 

Standards for medical electrical equipment

 
They belong into 4 main groups:
1. Safety (and essential performance) standards: requirements and test methods of compliance (so-called type tests to be performed at the manufacturer or in a test house).
2. Quality assurance standards: test methods for equipment in operation. These standards do not contain requirements, the applicable requirements are that of the safety standards, moreover, contractual or manufacturer’s specifications and somewhere some national and/or local regulations.
3. Performance standards: definitions and measuring methods of some characteristics of the equipment. These standards do not contain requirements, either. Their aim is to make background for testing according to other standards accurate and clear.
4. There is also one standard only for Electromagnetic compatibility (EMC).
It is important to note that for medical procedures themselves there are no standards.

 

Safety standard family of medical electrical equipment

 
– IEC 60601-1 Medical Electrical Equipment – Part 1: General requirements for basic safety and essential performance: the so-called general standard. “Essential performance”, i.e. performance which is essential also for safety, is first introduced in this standard but the so-called “system-based approach” is an even more characteristic feature of the 3rd edition. Its 3rd edition was accepted in December 2005 as IEC standard (and in September 2006 by CENELEC as Euronorm EN, European, and in March 2007 as Hungarian standard).
– IEC 60601-1-X: so-called collateral standards. They apply to groups of products, e.g. for X-ray equipment. Their requirements are also general but may be more easily revised than the general standard.
– IEC 60601-2-X: so-called particular standards. They apply to a given product type, e.g. a given modality of imaging equipment. They have priority over the general and the collateral standards.
Risk factors dealt with in safety standards are: electrical safety, mechanical safety, radiation protection, EMC, risk management, equipment systems, environmental protection, safety systems, biological compatibility, usability, software safety, data safety and security etc.
It is important to know that during conformance testing and certifying, it is not allowed to combine third edition of the general standard with collateral and particular standards, connected to the second edition. So third edition of the general standard may be combined only with the new (with it “harmonized”) collateral and particular standards only, if they already exist. Lack of a particular standard can be substituted with individual risk management but manufacturers try to avoid it because it is a complicated task.
As it was mentioned, CENELEC accepted the new general standard as EN standard in September 2006. According to requirements of CENELEC, member states are obliged from September 2009 to apply exclusively the new standards for medical electrical equipment. If there is no particular standard (yet) for a given equipment type than general standard must be supplemented by risk management. But in this case, if an old particular standard exists, application of the new general standard is obligatory only if the particular standard is revised, too. If it is not the case, there was allowed to apply old standards, till publication of the new edition of the particular standard. Revising particular standards of diagnostic radiology equipment is finished at the beginning of 2011, therefore – after transition periods elapsed – applying the old standards will be prohibited. Only elaboration of two new safety standards for dental radiology equipment demands a longer time.
Although application of standards – at least in the EU – is “not obligatory”, customers all over the world generally consider compliance to the applicable standards of IEC TC 62 as a necessary condition for purchasing medical electrical equipment. In EU, however, necessary condition for circulating a product is the CE marking, i.e. compliance with essential requirements of MDD (Medical Devices Directive). Application of standards, although they are not obligatory, is made possible by the fact that compliance with individual requirements of MDD may be replaced by compliance with the so-called harmonized standards. It must be noted that in the EU, according to aims of the regulation, only safety standards can be harmonized, quality assurance standards can not.

Quality assurance standard family of diagnostic radiology equipment

 
The IEC 61223 quality assurance standard family originally consisted from three series: the single 61223-1 defined general terminology, series 2 was the “Constancy tests” series while series 3 has the title “Acceptance tests”. Obviously, the latter were applicable also for status testing. First edition of these standards was elaborated in the 90s, except computed tomography which was issued in 2004. For mammography there is an updated second edition (2007). The older ones, although a part of their contents is applicable also in the future – with the rapid expansion of digital equipment – do not cover the full area to be tested. There was an attempt for their revising but it failed. In 2005, TC 62 made a decision about withdrawal of full “constancy testing” series (except CT), and in October 2010 “acceptance testing” standards, indicated in the next table with an asterisk, were also withdrawn, in spite of protest of Hungary. Reason for the withdrawal was that “these standards are not applied in the practice”, although “acceptance testing” standards (IEC/EN 61223-3 series) are used in some countries, including Hungary, for acceptance (and status) testing of equipment. (Most countries, however, even inside the EU, have own special requirements for acceptance testing.)
Withdrawal of standards does not exclude applying them but means that IEC does not consider these standards to be up-to-date any more. Accreditation of testing laboratories is possible also according to withdrawn standards. As, however, it is uncertain whether will be there ever a new edition of these standards, it is not practical to establish activities of testing laboratories on withdrawn standards but one has to find some up-to-date documents for this purpose. Such a European Guideline is already exists for mammography equipment (see 7, in Hungarian 9). We may hope that there will be such one for the full area of diagnostic radiology which may have a wide consensus, including manufacturers.

 
Table: New system of IEC standards, relating to diagnostic radiology equipment

 

Some interesting details from the radiation protection standard

 
The most problematic part of a standard is its scope. After long discussions, scope of the 2nd edition of IEC 60601-1-3 – which has been published in January 2008 – formulated as follows: “This Collateral Standard applies to X-ray equipment and to subassemblies of such equipment, where images of the patient are used for diagnosis, planning or guidance of medical procedures.”
With the technical development meaning of concepts of “radiography” and “radioscopy” (“fluoroscopy”) became old-fashioned: in modern equipment (pulsed) radioscopy and serial radiography differs only in value of X-ray tube current.
Creation of new definitions was very difficult. The accepted new definitions are the following: “Radiography: technique for obtaining, recording and optionally processing, directly or after transfer, information contained in an X-ray pattern at an image reception area intended to be analyzed during a time independent from the irradiation time.” “Radioscopy: technique for obtaining continuously or periodically a sequence of X-ray patterns and presenting them simultaneously and continuously as visible images, intended to provide a real-time guidance to an ongoing action.” The latter includes gastro-intestinal examinations with spotfilm device, interventional radiology, X-ray guided lithotripsy, surgical-traumatological fluoroscopy, stereotaxy, and radiation therapy simulation. It is unambiguous that fluoroscopy (“radioscopy”) is not a diagnostic procedure any more. A question is whether pulmonologists accept prohibition of fluoroscopy as diagnostic method, as they can localize lesions with fluoroscopy quickly and with a very little radiation exposure.
2nd edition of IEC 60601-1-3 contains numerical requirements only for radiation quality (half value layers) and leakage radiation, all other requirements are moved into the particular standards, mostly into the new IEC 60601-2-54 which was published in 2009, while dental related parts of it into the future dental safety standards.

 

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