DICOM Structured Reporting

Transcription

1 inforad 891 DICOM Structured Reporting Part 1. Overview and Characteristics 1 Rada Hussein, MSc Uwe Engelmann, PhD Andre Schroeter, MSc Hans-Peter Meinzer, PhD Supplement 23 to (DICOM) is an introduction to the structured reporting (SR) classes, which are used for transmission and storage of clinical documents. The SR classes fully support both conventional free-text reports and structured information, thus enhancing the precision, clarity, and value of clinical documentation. In addition, the SR standard provides the capability to link text and other data to particular images or waveforms and to store the coordinates of findings. In other words, SR documents not only describe the specific features contained in images or waveforms but can also refer to any number of images or waveforms. Accordingly, SR bridges the traditional gap between imaging systems and information systems. Furthermore, SR plays an essential role in Integrating the Healthcare Enterprise by providing healthcare practitioners with an effective tool that encompasses a variety of clinical contexts. Harmonization of DICOM SR and the Health Level Seven clinical document architecture standard is under way. RSNA, 2004 Abbreviations: CDA clinical document architecture, DCMR DICOM Content Mapping Resource, DICOM Digital Imaging and Communications in Medicine, HL7 Health Level Seven, IHE Integrating the Healthcare Enterprise, IOD information object definition, SOP service object pair, SR structured reporting Index terms: Computers Digital imaging and communications in medicine (DICOM) Information management Radiology reporting systems 2004; 24: Published online /rg From the Division of Medical and Biological Informatics, H0100, German Cancer Research Center, Im Neuenheimer Feld 280, D Heidelberg, Germany; and Steinbeis-Transferzentrum Medizinische Informatik, Heidelberg. Received May 30, 2003; revision requested August 4 and received August 20; accepted September 15. Address correspondence to R.H. ( r.hussein@dkfz-heidelberg.de). See also the article by Hussein et al (pp ) in this issue. RSNA, 2004

2 892 May-June 2004 RG f Volume 24 Number 3 Figure 1. Diagrams of SR trees. Introduction Practical experience has shown that use of structured forms for reporting reduces the ambiguity of natural language format reports and enhances the precision, clarity, and value of clinical documents. At the technical level, structured reporting (SR) is the optimal form of documentation in computerized systems, as it allows searching, storage, and comparison with similar data elements. Consequently, Digital Imaging and Communications in Medicine (DICOM) SR has emerged to increase the efficiency of the distribution of information between the various specialties (1). In practice, SR can be widely used in a variety of clinical contexts. Examples include the following: (a) In computed tomography or magnetic resonance imaging, it can be used to represent the interpretations, to link the referenced images, and to record the spatial coordinates of significant findings. (b) In ultrasound (US), it can be used to record and transmit the measurements. (c) In cardiac catheterization laboratories, it can be used to record a procedure log and to link together all related information and DICOM objects into a convenient unit-record. Furthermore, the DICOM Key Object Selection Document, which is based on DICOM SR, was recently introduced (2) to facilitate flagging or selection of one or more significant images, waveforms, or other DICOM objects from one or more studies for a patient. This article briefly presents some background on SR document structure and management, DICOM SR templates, and key image notes. In addition, Integrating the Healthcare Enterprise (IHE) and the Health Level Seven (HL7) clinical document architecture (CDA) are introduced to highlight the approaches to exchanging structured documents within the healthcare environment. Structure of SR Documents DICOM SR is a document architecture designed for encoding and exchanging information by using the DICOM hierarchical structure and services (3,4). In other words, DICOM SR introduces DICOM information object definitions (IODs) and services used for the storage and transmission of structured reports. The DICOM IODs define the data structures that describe the information objects of real-world objects (eg, patients, images, reports) that are involved in radiology operations. The DICOM services are concerned with storage, query, retrieval, and transfer of data. Basically, an SR document consists of a sequence of nodes called Content Items that are linked together with relationships in a tree form (Fig 1) (5). Each content item is represented by a name/value pair. The name refers more precisely to a single Concept Name, which is defined by a code rather than by free text to facilitate indexing and searching. Therefore, any concept name is represented by a coded entry that uses triplet encoding attributes as follows: (a) the code value, which is a computer-readable and -searchable identifier; (b) the code scheme designator, which is an identifier of the coding organization; and (c) the code meaning, in which human-readable

3 RG f Volume 24 Number 3 Hussein et al 893 Figure 2. The SR information model. ROI region of interest, SOP service object pair, UID unique identifier. Example of an SR tree. PA posteroante- Figure 3. rior. text is entered to be displayed. The value of a content item could be one of the values in Figure 2. The parent content item (ie, parent node) can be linked to a child content item (ie, child node) with one of the relationships in Figure 1. For example, a radiography report (posteroanterior and lateral views) may contain the following finding and conclusion sections: The finding is a mass measuring 1.3 cm in diameter with an infiltrative margination. The conclusion is a probable malignancy, inferred from the infiltrative margination of the mass. This report can be represented in an SR document structure (Fig 3). SR SOP Classes The DICOM SR standard specifies three generalpurpose SR SOP classes of increasing complexity to cover the vast SR applications. These are defined as follows: 1. The basic text SR IOD is used to represent simple reports that use a minimal amount of coded entries. References are allowed only at the leaves level of the SR textual tree with no by-reference content items (ie, a by-value relationship only is allowed). 2. The enhanced SR IOD, a superset of basic text SR, is used to represent simple reports that include spatial and temporal regions of interest. 3. The comprehensive SR IOD, a superset of basic text and enhanced SR, is used to represent complex reporting without any restrictions of references. Management of SR Documents In addition to reports creation and encoding, the DICOM SR standard provides managerial rules to control the storing of documents and their availability wherever needed. These rules specifically manage the whence of the coming documents, the destination of the currently created/ revised documents, the version of the used document, and how to get the relevant documents. To simplify the SR queries, the SR managerial attributes are stored outside the SR tree (ie, in a separate module called the SR Document General Module). These attributes include the following:

4 894 May-June 2004 RG f Volume 24 Number 3 Figure 4. Template for the basic diagnostic imaging report as given in the DCMR (template identifier 2000). (a) the document identification attributes (eg, the SOP unique identifier, SOP instance unique identifier, instance number, content date, and content time); (b) the document status and verification attributes (eg, the completion flag [either partially or fully completed document], completion flag description, verification flag [either unverified or verified document], and sequences of the verifying observers); (c) the reference request sequence, which identifies requested procedure(s) being fulfilled by the SR document; (d) the related documents (eg, the predecessor document sequence); and (e) the identical documents sequence, which references all identical SR documents. SR Templates The different patterns of the SR applications are called SR Templates and are addressed in a separate DICOM part titled DICOM Content Mapping Resource (DCMR) (6). These patterns describe and constrain the content items, value types, relationship types, and value sets that may be used in either part of the SR documents trees or the overall tree for a specific reporting application. There are different DICOM working groups for different SR specialties, and they provide the corresponding templates in separate DICOM supplements (7). Examples include the following: DICOM Working Group 15 provides the computer-aided detection (CAD) templates for mammography in supplement 50, the chest CAD templates in supplement 65, the patient history in supplement 75, and the breast report in supplement 79. DICOM Working Group 1 provides the catheterization laboratory structured reports in supplement 66, the ventriculography structured reports in supplement 76, and the intravascular US structured reports in supplement 77. DICOM Working Group 12 provides the US obstetrics and gynecology procedure reports in supplement 26, the vascular US procedure reports in supplement 71, the echocardiography procedure reports in supplement 72, and the fetal and pediatric echocardiography structured reports in supplement 78. With finalization of these supplements, the proposed templates are added to the DCMR part of the DICOM standard. The main purpose of DCMR is to define the templates and context groups used in the DICOM standard by using multiple coding standards, such as the Systematized Nomenclature of Medicine (SNOMED)

5 RG f Volume 24 Number 3 Hussein et al 895 and Logical Observation Identifier Names and Codes (LOINC). Figure 4 shows a sample of the SR template in which the basic diagnostic imaging report is defined by using tables of the appeared form. Ultimately, DICOM Working Group 8 works to provide an extensible markup language (XML) schema that will be flexible enough to represent all data contained in DICOM SR. Role of SR in IHE In 1997, the IHE initiative was launched to promote and support the integration of healthcare information systems. IHE is not a standard; it ensures actual implementations of truly interpretational systems by filling the gaps between wellestablished bodies of communications standards in healthcare, such as DICOM for image data (7) and HL7 for text data (8). IHE offers a rigorously organized technical framework that provides a comprehensive guide for a coordinated implementation of information standards. The IHE integration profiles are defined in the IHE technical framework to provide a convenient way of representing real-world integration problems and solution scenarios (9). IHE recognizes the added value of implementing these new DICOM additions (10). Therefore, it enriches the IHE technical framework with extensive use of SR in three IHE integration profiles (11): 1. The Access to Radiology Information integration profile provides a well-defined means for delivering radiologic information (images and related reports) to non-ris (radiology information system) systems and users. 2. The Simple Image and Numeric Reports integration profile is used for exchanging simple reports with image links. 3. The Key Image Note integration profile is used for flagging significant images. The key image note pattern was introduced by IHE to make it possible to flag particular images in a study as being of interest. Key Image Notes The key image note pattern was introduced in the IHE technical framework. It represents a simple pattern for marking one or more images in a study as significant for various purposes, such as referring physician access, teaching files selection, consultation with other departments, and image quality issues. Hence, a note is attached to the images and managed together with the study. A typical note may include a title to state the purpose of marking the images, references to images, a user comment, and optionally the observation context. Harmonization of SR and the CDA Standard The HL7 organization has developed the CDA standard, which was initially known as the Patient Record Architecture (PRA), for the healthcare industry (8). The CDA standard is based on extensible markup language (XML) and is mainly designed to provide an exchange model for clinical documents such as discharge summaries and progress notes. The complete CDA will include a hierarchical set of documentation specifications. The current CDA standard has defined only the top hierarchy, which is known as CDA Level One and became an American National Standards Institute (ANSI) approved standard in It represents the first specification derived from the central HL7 Reference Information Model (RIM). CDA Level Two is a set of templates or constraints that can be layered on top of the CDA level. CDA Level Three will include a fully SRcompatible model to enable SR documents to exchange information with non-dicom devices, such as information systems. This harmonization process is currently being undertaken by DICOM Working Group 20 (the Integration of Imaging and Information Systems Group) and the HL7 Imaging Integration Special Interest Group (IISIG). Conclusions Today, SR has become a powerful format that improves the expressiveness, precision, and comparability of clinical documentation. Moreover, SR provides the capability to link the clinical document to the DICOM images and waveforms from which these reports and measurements are made. Accordingly, images and reports can be displayed simultaneously at the same workstation. From the computerized systems perspective, SR is a databaseable document format that facilitates computer search analysis for various purposes, such as scientific research, education, training, clinical trials, performance evaluation, and eventually integration with data mining applications. In any DICOM-based clinical context, SR has many potential advantages, such as improved report turnaround time; the production of complete, accurate, and well-organized reports; and the ability to communicate results promptly. Consequently, improved diagnostic accuracy can be achieved with more speed, reduced overall costs, fewer errors, and better management.

6 896 May-June 2004 RG f Volume 24 Number 3 References 1. National Electrical Manufacturers Association. (DICOM), supplement 23: structured reporting storage SOP classes. Rosslyn, Va: NEMA, Available at: 2. National Electrical Manufacturers Association. (DICOM), supplement 59: Key Object Selection Document SOP class. Rosslyn, Va: NEMA, Available at: 3. National Electrical Manufacturers Association. (DICOM), part 3: information object definitions. Rosslyn, Va: NEMA, Available at: medical.nema.org/dicom/2003.html. 4. National Electrical Manufacturers Association. (DICOM), part 4: service class specifications. Rosslyn, Va: NEMA, Available at: medical.nema.org/dicom/2003.html. 5. Clunie D. DICOM structured reporting. Bangor, Pa: PixelMed, National Electrical Manufacturers Association. (DICOM), part 16: Content Mapping Resource. Rosslyn, Va: NEMA, Available at: medical.nema.org/dicom/2003.html. 7. National Electrical Manufacturers Association. (DICOM). NEMA Standard Publications PS 3.x. Rosslyn, Va: NEMA, Available at: 8. Health Level Seven. Application protocol of electronic data exchange in healthcare environments, version 2.4. Ann Arbor, Mich: HL7, October Available at: 9. Radiological Society of North America/Healthcare Information and Management Systems Society. IHE technical framework, year 4, revision 5.3. Oak Brook, Ill: RSNA, April Available at: Henderson M, Behlen F, Parisot C, et al. Integrating the Healthcare Enterprise: a primer. IV. The role of existing standards in IHE. 2001; 21: Channin DS. Integrating the Healthcare Enterprise: a primer. II. Seven brides for seven brothers: the IHE integration profiles. 2001; 21: