In the medical sector, the DICOM Standard (Digital Imaging and Communication in Medicine) regulates the digital image management since more than 20 years. It defines the communication and exchange of data between (patient) administration systems, imaging modalities and storage archives and is established worldwide with manufacturers of modalities and software as well as hospitals and users.
The advantages of DICOM for the medical area have been uncovered by ASTM for the industrial material testing. In 2004, after a 5-year development phase, the initial version of DICONDE (Digital Imaging and Communication in Non-Destructive Evaluation) has been introduced as ASTM E2339. Today, this universal and vendor neutral standard has been extended to all common procedures of destructive and non-destructive material testing (see ASTM E2663, E2699, E2738, E2767, E2934).
There are many reasons why DICONDE should be used as the standard file format as well as for data communication in NDT.
1. DICONDE supports all image and data types in NDT
Image and signal data can be stored at various file formats. The purpose of further processing should be meaningfully define the type of format. If, for example, smallest inclusions and pores have to be diagnosed in images of welding seams, it might become crucial to not use JPEG for storing the original/raw data since artefacts of the lossy compression algorithm might eliminate small details irrevocably. Other data, such as video streams in VT testing in contrast, have to undergo a certain compression technique to get rid of the tremendous amount of incoming data.
The DICONDE standard defines container for lossless and lossy storage of image, video and signal data as well as documents, e.g. PDF.
The biggest advantage is generated by the structured meta data (tags) included in every file. For each image or content object, a precisely defined set of information is added, starting with the name and ID of the component tested, the order/accession number, image date and time as well as spatial resolution, color- or grayscale settings and relevant parameters of the imaging modality up to information of environmental conditions at the time of recording.
Since every DICONDE file must have a properly filled meta data container to become valid, answers to context searches become easy and database structures can be rebuild at any time from the files themselves. No other (image) file format offers comparable options.
2. DICONDE stands for and creates independence from vendors
Every single data field/tag of a DICONDE files is well defined – the standard leaves no room for varying interpretations. This guarantees same as with DICOM in medicine, that every software for storing, communication or visualizing DICONDE data produces the same results. This applies to image/video data as well as meta data and assures a vendor neutral interoperability. A fully conformant DICONDE file encoding additionally ensures readability and compatibility for a long period of time – more on this topic follows below.
3. DICONDE defines data structures as well as protocols
Next to data (file) structures, DICONDE defines a set of network communication protocols based on TCP/IP. These guarantee that all attached devices talk the same language. For instance, an RT-D scanner can fetch the order data digitally (DICONDE Modality Worklist) and stores the created images to a server (DICONDE Storage) that sends back an acknowledgement of a successful receipt (DICONDE Storage Commitment).
Moreover, DICONDE compliant systems can query and exchange data via the Query/Retrieve protocol.
4. DICONDE contributes to a process based, digital workflow
The communication protocols allow the implementation of a seamless, fully digital workflow: Inspection orders are created by the supervising system (ERP, RBI, MES) and published as worklists to the imaging modalities. At the time of creation, a part of the metadata of the DICONDE image files is populated from that worklist. The imaging system delivers the other part, e.g. parameters about image geometry and x-ray exposition. The crucial point is that inalterable information like the ID and name of the component tested are transported digitally – and stay the same also for recurrent images of the same object in the context of operational safety inspections. This assures that image studies can be found quickly and reviews as temporal sequences, e.g. for comparing aging effects, etc.
After a successful receipt and storage of the images, a digital notification can be send to the supervising system and metadata can be made available to the next systems in the workflow, e.g. an application for the inspection report creation.
5. DICONDE guarantees data integrity across systems
The pixel data written to the DICONDE file at creation time (raw data) stay inalterable and are protected from manipulation during all subsequent processing steps. Markers, measurements and modifications of window level, brightness and contrast are stored as additional information in a separate, but associated DICONDE object. A continuous digital workflow as described in the prior chapter guarantees that metadata of every DICONDE object is identical to the information stored in the supervising system that places the inspection order. This assures data integrity in all connected software systems in the process.
The network protocols of DICONDE guarantee, by design, a monitoring of the complete data transfer – if a single byte is missing, the validation fails and the transfer will be (automatically) repeated.
6. DICONDE is recommended for long term archiving
Any data that are created in the context of an inspection process, including the image data, are automatically classified as operational maintenance documents and thus have to be stored for a minimum of 10 years – or maybe even longer if specific engineering standards are applicable. Many data/file formats do change over time or/and have no option to identify manipulations and are thus no wise choice for a revision-save, long-term archiving.
Based on DICOM that has been established as long-term storage file format since almost 20 years and that has a guaranteed backwards compatibility of the versions of the standard, DICONDE is well prepared to take the archiving job for digital data in NDT.
Since DICONDE stores all meta information of each inspected component together with its pixel data in one file, DICONDE data is always structured. If inspection image data are archived e.g. as JPEG files, an associated database with the related metadata information (component ID, name, etc.) must always be stored together with the images. A later migration of such JPG images while keeping the data integer becomes a difficult task or even impossible.
7. DICONDE means security of investment
As an open standard managed by a non-profit organization and not constrained by any development licenses costs, DICONDE guarantees the highest possible security of investment and follows the paradigm of DICOM also in this aspect.
With a high quality and accuracy in its definitions, DICONDE does not tolerate any variability in its interpretation and thus guarantees that implemented software products of different vendors can always interoperate without problems. An exchange and migration of data between products of different companies is possible at any time and would even allow customers for a change of vendor without converting or re-writing files that have already been archived.
Because of its interoperability, its qualification for archiving and integration in digital processes, DICONDE is a meaningful invest for an implementation of digital material testing processes in "Industry 4.0".