The world of medical imaging standards and compliance certification by conformity assessment bodies

Brussels 28 March 2000Implementation was the central theme in the fourth session of the MediMedia workshop on medical imaging. Joël Chabriais, M.D. at the Hôpital Necker in Paris, addressed the issue of standardisation which covers an extensive field. There are various actors, divided into international, European, and national organisations, responsible for general, specific, and telecommunication standards. In his presentation, Dr. Chabriais exclusively dealt with standards that are applicable in the Health Informatics area, such as ISO TC 215, CEN TC 251, AFNOR, DICOM, and HL7.

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There are two distinct families of standards in health information technology, respectively relating to hardware and software. In the software branch, ISO TC 215 which is expected by 2002, constitutes the international standard. A European standard, CEN TC 251, has been published recently. In 1993, the specialist standard for medical imaging and communications, DICOM, was issued. Since then, this standard has been updated with a new release each year. The HL7 and EDI standards cover the field of messaging and are maintained by independent committees.

In the field of Health Informatics the interoperability between various devices and the exchange of data among different sources constitute a major issue, according to Dr. Chabriais. Standards allow us to transmit clinical data and images from the electronic patient folder to different hospital sites, requiring these elements for diagnosis and treatment. Medical image examination is a subset of the medical image folder, including a request, summaries, images, prescription, preparations for contrast media, reports of specimen analysis, and other elements.

The standards involved are DICOM, HL7, Corbamed, and EDI, as to facilitate admission, order entry, image acquisition, results reporting, and billing. It is quite obvious that there is a need for further integration and for standards to evolve, as stated by Dr. Chabriais. Initially, the DICOM standard just covered a few image modalities like Computed Tomography (CT), Magnetic Resonance (MR), and computer radiology. DICOM is complex, involving several elements such as images, storage services, image folder retrieval, and ICT networking support.

DICOM was extended to cardiology applications in 1995; ultrasound, nuclear medicine, and PET in 1996; radiotherapy and visible light in 1997; digital x-ray mammography and radiology, and vital signs in 1998; audio & oral waveform, electrocardiograms, and visible light for endoscopy and pathology in 1999. Currently, there are 20 working groups in the DICOM committee, two of which are recent and very important. The first one is responsible for providing a method to flag images for clinical trial and education purposes, trying to integrate them into the research protocol.

The second one is working on the integration of imaging & information systems, using the standards HL7, ISO TC 215, and CEN. DICOM does not standardise compression but uses as a standard for compression JPEG LS at present, and JPEG 2000 in the future. The new supplement 254 is now on public command. It is the so-called DICOM MIME type, which allows to encapsulate DICOM objects into e-mail by means of the MIME protocol. This is the DICOM Web and e-mail initiative in order to integrate DICOM with web technology. Links are now being established between ISO TC 215, HL7 and DICOM to avoid stagnation in the standardisation process.

Dr. Chabriais thinks it absolutely necessary to comply to standards because interoperability has to be ensured. In addition, users should be informed of this compliance through the principles of conformance statement, standard body mark, and certification and conformity assessment. There are 2 types of conformance, namely dynamic and static. Dynamic conformance applies to all those requirements which are permitted by the standard, while static conformance is a statement that a particular application corresponds to all that is implemented by the standard.

Before deciding to purchase a medical device, the customer has to check the conformance statement in order to be sure that the product really offers the required services to be integrated. The standard body mark consists of a CE or NF mark, which is the property of the standard body to guarantee that the product meets the applicable standards. In this regard, it is easier to obtain a European CE mark than an agreement, issued by the U.S. Food and Drug Administration, according to Dr. Chabriais. The CE mark does not detail the conformance statement.

In contrast with a CE mark, the certification and conformity assessment are more difficult to acquire because they are provided by independent bodies. This third party verification is paid for by the manufacturer. The full process of conformity assessment takes time which makes it impossible to perform this procedure for each new, annual release of a given standard. Therefore, the European Community has recommended the member states to establish national accreditation bodies as a means to prove the technical competence of the conformity assessment bodies, often mandatory to certain authorised fields.


Leslie Versweyveld

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