Image acquisition context: procedure description attributes for clinically relevant indexing and selective retrieval of biomedical images.

OBJECTIVE: To support clinically relevant indexing of biomedical images and image-related information based on the attributes of image acquisition procedures and the judgments (observations) expressed by observers in the process of image interpretation. DESIGN: The authors introduce the notion of "image acquisition context," the set of attributes that describe image acquisition procedures, and present a standards-based strategy for utilizing the attributes of image acquisition context as indexing and retrieval keys for digital image libraries. METHODS: The authors' indexing strategy is based on an interdependent message/terminology architecture that combines the Digital Imaging and Communication in Medicine (DICOM) standard, the SNOMED (Systematized Nomenclature of Human and Veterinary Medicine) vocabulary, and the SNOMED DICOM microglossary. The SNOMED DICOM microglossary provides context-dependent mapping of terminology to DICOM data elements. RESULTS: The capability of embedding standard coded descriptors in DICOM image headers and image-interpretation reports improves the potential for selective retrieval of image-related information. This favorably affects information management in digital libraries.

The SNOMED DICOM microglossary: controlled terminology resource for data interchange in biomedical imaging.

This paper describes an authoritative, non-proprietary information resource that provides an efficient mechanism for embedding specialized clinical knowledge into the design of healthcare telecommunications systems. The resource marries two types of data interchange standards, a message/electronic-document standard and a terminology standard. In technical terms, it is part protocol and part database. Industry, academia, professional specialty societies, and the federal government participated in its development. The development of multi-specialty content has broadly engaged biomedical domain experts to an unprecedented degree in voluntary, non-proprietary message/document-standards development. The resource is the SNOMED DICOM Microglossary (SDM), a message-terminology (or document-content) mapping resource. The message/electronic-document standard is DICOM (Digital Imaging and Communications in Medicine). The terminology standard is SNOMED, (Systematized Nomenclature of Human and Veterinary Medicine). The SDM specifies the mapping of multi-specialty imaging terminology from SNOMED to DICOM data elements. DICOM provides semantic constraints and a framework for discourse that are lacking in SNOMED. Thus the message standard and the computer-based terminology both depend upon and complete each other. The combination is synergistic. By substitution of different templates of specialty terminology from the SDM, a generic message template, such as the DICOM Visible Light (Color Diagnostic) Image or the DICOM Structured Reporting specification can be reconfigured for diverse applications. Professional societies, with technical assistance from the College of American Pathologists, contribute and maintain their portions of the terminology, and can use SDM templates and term lists in clinical practice guidelines for the structure and content of computer-based patient records.

Development of the Logical Observation Identifier Names and Codes (LOINC) vocabulary.

The LOINC (Logical Observation Identifier Names and Codes) vocabulary is a set of more than 10,000 names and codes developed for use as observation identifiers in standardized messages exchanged between clinical computer systems. The goal of the study was to create universal names and codes for clinical observations that could be used by all clinical information systems. The LOINC names are structured to facilitate rapid matching, either automated or manual, between local vocabularies and the universal LOINC codes. If LOINC codes are used in clinical messages, each system participating in data exchange needs to match its local vocabulary to the standard vocabulary only once. This will reduce both the time and cost of implementing standardized interfaces. The history of the development of the LOINC vocabulary and the methodology used in its creation are described.

The role of digital imaging and communications in medicine in an evolving healthcare computing environment: the model is the message.

The decision to use Digital Imaging and Communications in Medicine (DICOM), Health Level 7 (HL7), a common object broker such as the Common Object Request Brokering Architecture (CORBA) or ActiveX (Microsoft Corp, Redmond, WA) or any other protocol for the transfer of DICOM data depends on the requirements of a particular implementation. The selection of protocol is independent of the information model. Our goal as message standards developers is to design a data interchange infrastructure that will faithfully convey the computer-based patient record and make it available to authorized health care providers when and where it is needed for patient care. DICOM accurately and expressively represents the clinically significant properties of images and the semantics of image-related information. The DICOM data model is small and well-defined. The model can be expressed in Standard Generalized Markup Language (SGML) or Object Management Group Interface Definition Language or other common syntax-and can be implemented using any reliable communications protocol. Therefore our opinion is that the DICOM semantic data model should serve as the basis for a logically equivalent set of specifications in HL7, CORBA, ActiveX, and SGML for the interchange of biomedical images and image-related information.

A proposal for incorporating health level seven (HL7) vocabulary in the UMLS Metathesaurus.

The HL7 Vocabulary Technical Committee (TC) was organized to select and maintain the vocabulary used in HL7 messages. The goal is to make implementations of the Version 3 HL7 Standard more plug-and-play compatible. In order to make the vocabulary readily accessible to the public, HL7 is collaborating with the U.S. National Library of Medicine (NLM) to include HL7 vocabulary in the Unified Medical Language System (UMLS) Metathesaurus. This article describes a proposal for how HL7 data elements and coded values can be represented accurately in the relational tables of the UMLS Metathesaurus.

Clinical importance of the DICOM structured reporting standard.

The purpose of the DICOM Structured Reporting (SR) specification is to improve the documentation of diagnostic images and waveforms. The specification supports the interchange of expressive compound reports in which the critical features shown by images and waveforms can be denoted unambiguously by the observer, indexed, and retrieved selectively by subsequent reviewers. Findings may be expressed by the observer as: 1) text, codes, numeric measurements: 2) computer-generated coordinates of specific regions of interest within images or waveforms; or 3) reference to comparison images, sound, waveforms, curves, and previous report information. The observational and historical findings recorded by the observer may include any evidence referenced as part of an interpretation procedure. Thus, DICOM SR supports not only the reporting of diagnostic observations, but the capability to document fully the evidence that evoked the observations. This capability provides significant new opportunities for large-scale collection of structured data for clinical research, training, and outcomes assessment as a routine by-product of diagnostic image and waveform interpretation and facilitates the pooling of structured data for multi-center clinical trials and evaluations.

Understanding and using DICOM, the data interchange standard for biomedical imaging.

The Digital Imaging and Communications in Medicine (DICOM) Standard specifies a non-proprietary data interchange protocol, digital image format, and file structure for biomedical images and image-related information. The fundamental concepts of the DICOM message protocol, services, and information objects are reviewed as background for a detailed discussion of the functionality of DICOM; the innovations and limitations of the Standard; and the impact of various DICOM features on information system users. DICOM addresses five general application areas: (1) network image management, (2) network image interpretation management, (3) network print management, (4) imaging procedure management, (5) off-line storage media management. DICOM is a complete specification of the elements required to achieve a practical level of automatic interoperability between biomedical imaging computer systems--from application layer to bit-stream encoding. The Standard is being extended and expanded in modular fashion to support new applications and incorporate new technology. An interface to other Information Systems provides for shared management of patient, procedure, and results information related to images. A Conformance Statement template enables a knowledgeable user to determine if interoperability between two implementations is possible. Knowledge of DICOM's benefits and realistic understanding of its limitations enable one to use the Standard effectively as the basis for a long term implementation strategy for image management and communications systems.

Documenting the information content of images.

A standards-based message and terminology architecture has been specified to enable large-scale open and non-proprietary interchange of imaging-procedure descriptions and image-interpretation reports providing semantically-rich linkage of linguistic and non-linguistic information. The DICOM Structured Reporting Supplement, now available for trial use, embodies this interdependent message/terminology architecture. A DICOM structured report object is a self-describing information structure that can be tailored to support diverse clinical observation reporting applications by utilization of templates and context-dependent terminology from an external message/terminology mapping resource such as the SNOMED DICOM Microglossary (SDM), HL7 Vocabulary, or Terminology Resource for Message Standards (TeRMS).

Representation of the Gastrointestinal Endoscopy Minimal Standard Terminology in the SNOMED DICOM microglossary.

In Gastroenterology, endoscopic images and interpretation reports are essential elements of the patient record. The Digital Imaging and Communications in Medicine (DICOM) Visible Light and Structured Reporting Standards provide a standard representation of images and reports. However, the message standards are not sufficient in themselves. Controlled terminology is needed to enable interchange of patient records and to facilitate the pooling of multi-center data for large-scale outcomes studies and clinical research. The ASGE has joined with European and Japanese colleagues to develop and publish a lexicon of endoscopic terminology. The lexicon is being tested now in a multi-center trial. In addition, the ASGE is collaborating with the DICOM Standards Committee to transform the endoscopic lexicon into a database structure that is suitable for use with the DICOM Visible Light and Structured Reporting Standards. The combination of an internationally accepted, tested and non-proprietary lexical standard and a DICOM message standard supporting endoscopic images and reports represents a powerful tool for clinicians to improve communication, research and the quality of care.

Conceptual schemata for terminology: a continuum from headings to values in patient records and messages.

We developed a technique of reverse engineering to extract a conceptual schema--also called "categorial structure" in the European standard CEN ENV 12264 (MoSe)--from a set of terminological phrases. The technique was originally applied to coding systems, ie. to large value sets. We applied this technique to subsets of two new terminological resources for message standards: headings of patient record from Clinical LOINC and names of "Context Groups" for structured reporting from SNOMED DICOM Microglossary (SDM). Both sources provide context-independent names for message fields and domains of admitted values. Therefore conceptual schemata on the potential content for a field are compatible with the ones on names of the fields themselves. Both kinds of schemata can be compared and integrated with conceptual schemata for the information system that manages the patient record. This continuity in the schemata allows the coupling of applications with different organization of data, and will facilitate mapping from an application to standard messages and viceversa. Moreover, the simplified representation produced according the MoSe approach is easy to understand by healthcare operators, allowing their progressive involvement in cooperative efforts of design, discussion and validation of the schemata.

Modular extension of the ACR-NEMA DICOM standard to support new diagnostic imaging modalities and services.

The American College of Radiology-National Electrical Manufacturers Association (ACR-NEMA) Standard for Digital Imaging and Communications in Medicine (DICOM) (NEMA PS3-1993, DICOM) enables interconnection of imaging equipment and exchange of diagnostic images over standard networks. The widespread adoption of DICOM by industry and the benefits of standardized image management have attracted international attention. Other medical specialties, dentistry, and veterinary medicine have indicated strong interest in extending the DICOM Standard to support nonradiological image modalities. Parts 1 through 9 of DICOM were published in 1992 and 1993. Additional features developed in response to requests from the user community are being added in DICOM Supplements. The ACR, NEMA, and committees from other medical specialties working under the coordination of the American National Standards Institute Healthcare Informatics Standards Planning Panel Message Standards Developers Subcommittee Joint Working Group for Diagnostic Image Communication have defined new image object classes to support X-Ray Angiography, Radio-Fluoroscopy, Positron Emission Tomography, Endoscopy, and Light Microscopy. ACR-NEMA has also developed new service classes for Storage Commitment and Worklist Management. In joint work with the standards development committee of the Japanese Industries for Radiation Apparatus and the Japanese Medical Information System Development Center, ACR-NEMA has developed specifications for multibyte character set support and for a DICOM file format for transportable media. Other work is in progress. New DICOM features have provided and can continue to provide significant new functionality for digital image management systems. The demonstrated capability of efficient extension of the base standard is evidence of the effectiveness of the object oriented strategy of DICOM.

Magnetic resonance imaging of tophaceous gout in the hands and wrists.

The objective of this study was to determine the relative usefulness of physical examination, plain radiographs, and magnetic resonance imaging (MRI) using T1- and T2-weighted spin-echo images in evaluating the extent of urate deposition and soft tissue destruction in gouty arthritis. Seven patients with chronic tophaceous gout of the hands and wrists were examined to identify all clinically apparent tophi. Plain radiographs of the hands and wrist were obtained to further quantify soft tissue and osseous changes. MRI was then performed of the involved areas and a comparison made between soft tissue and bony changes observed by clinical examination and plain radiographs and those observed by MRI. Plain radiographs and physical examination markedly underestimate the size and extent of soft tissue and osseous involvement by tophi when compared with the findings of MRI. MRI also detects early, subclinical tophaceous deposits and indicates that urate deposits appear to spread along compartmental and fascial planes as opposed to the traditional view of strict radial growth. MRI is a useful method of determining the extent of disease in tophaceous gout and may provide information regarding the patterns of deposition and spread of monosodium urate crystals.

Interpretation time of serial chest CT examinations with stacked-metaphor workstation versus film alternator.

PURPOSE: Interpretation time of serial staging chest CT cases, which each contained current and previous examinations, with a simple prototype workstation called filmstack was experimentally compared with interpretation time with a film alternator. MATERIALS AND METHODS: The filmstack displayed a "stack" of sections for each examination; user controls allowed rapid selection of preset attenuation windows and both synchronized and unsynchronized scrolling. Eight radiologists were timed as they used the filmstack and the film alternator to interpret four ergonomically complex serial CT cases. RESULTS: All reports dictated on the basis of findings with filmstack and film were of acceptable clinical accuracy. The time to examine a case with filmstack was significantly faster than the time with film, including the time to load and unload the alternator (99% confidence [P = .01]). There was no statistically significant difference in interpretation time between filmstack and prehung film. CONCLUSION: Use of a low-cost stacked CT workstation with a single 1,024 x 1,024 monitor is an effective means of interpreting cases that require comparison of multiple CT examinations.

An imaging standard for dentistry. Extension of the radiology DICOM standard.

No standard exists for electronic communication of dental images. However, maxillofacial radiology, being part of general radiology, does have the advantage of having an applicable standard: The American College of Radiology-National Electrical Manufacturers Association Standard for Digital Imaging and Communications in Medicine (Version 3.0). This standard encourages open systems interconnection of imaging equipment over standard networks while maintaining compatibility with earlier point-to-point connection standards. This standard, to be voted on in 1993, moves the American College of Radiology-National Electrical Manufacturers Association into full conformance with the International Standards Organization reference model for network communications. An object-oriented information model lays the groundwork for harmonization with other medical communications standards. This article outlines the American College of Radiology-National Electrical Manufacturers Association components and discusses the rationale of object-oriented design. The relevance of the standard to dentistry is discussed.

Fat tissue and fat suppression.

Fat tissues consist of fat cells, capillaries, and collagen fibers. In order to completely suppress the signals from fat tissues in clinical magnetic resonance imaging, the signal from capillaries and collagen fibers as well as from fat cells should all be suppressed. We have previously reported that fat signal can be uniformly suppressed by applying an optimized presaturation pulse. The inhomogeneously broadened fat peak of tissue spectrum is excited by the optimized pulse and dephased by a subsequent field gradient. The broadened water peak is not affected. In this paper we discuss a technique that suppresses signals from fat tissues completely as well as uniformly. This technique is based on the cancellation of fat and water signals in the same image voxel by combining the optimized selective excitation with the opposite phase imaging technique. Experimental and clinical images demonstrate that the new technique improves the delineation and depiction of anatomy in clinical fat suppression imaging.

In search of the name.

Existing communications standards represent person name, date, time, and other ubiquitous attributes in various incompatible formats. The electronic medical record requires convergence of diverse representational systems toward a single communications standard or a harmonized group of standards. The obstacles to convergence include disparities in semantic definition, syntax, and communications protocols. To facilitate harmonization of existing standards, the message standards developers subcommittee of the ANSI HISPP (American National Standards Institute Healthcare Informatics Standards Planning Panel) has defined a set of common data types to facilitate semantic convergence. The authors present the general method used to develop the common data types. The derivation of the person name common data type is presented in detail. A general semantic model of the person name attribute is developed from observations of international usage conventions. A superset of the person name formats of the ACR-NEMA, ASTM, HL7, NCPDP, MEDIX, and X-12 standards is taken as the provisional starting point for a common data type definition. The convergence superset is compared with the general semantic model. Highly specialized and/or infrequently encountered sub components of the general model are combined into component complexes, thereby defining mappings to less rigorous representations. The ANSI HISPP common data types are specified for use in a demonstration of a prototype object-oriented HL7-DICOM HIS/PACS interface (between hospital information systems and imaging systems) at the 1993 Annual Meeting of the Radiological Society of North America.

Enhancement and demyelination of the intraorbital optic nerve. Fat suppression magnetic resonance imaging.

Conventional spin-echo magnetic resonance imaging (MRI) of intraorbital optic neuritis is hampered by the adjacent high signal and chemical shift artifact of orbital fat. Frequency-selective saturation pulse MRI reduces these problems and was used to determine its utility in evaluation of intraorbital optic neuritis. Eight consecutive patients with optic neuritis underwent MRI within 1 week of the onset of visual loss. Conventional MRI with T1, proton density, and T2 weighting and frequency-selective saturation pulse MRI with T1, proton density, and T2 weighting were performed. After administration of intravenous gadopentetate dimeglumine, T1-weighted conventional and frequency-selective saturation pulse MRI were performed. Frequency-selective saturation pulse MRI showed gadopentetate dimeglumine enhancement in the intraorbital optic nerve in 7 patients and the intracranial optic nerve in 3 patients. Conventional MRI failed to show optic nerve gadopentetate dimeglumine enhancement in patients with intraorbital lesions, but did show intracranial lesions. Frequency-selective saturation pulse MRI showed bilateral optic nerve enhancement in 3 patients with unilateral visual signs and symptoms. Proton density and T2-weighted conventional MRI of the brain showed no convincing signal aberrations in the optic nerves. In the MRI evaluation of intraorbital optic neuritis: (1) frequency-selective saturation pulse fat suppression MRI is superior to T1-weighted conventional MRI in the detection of gadopentetate dimeglumine enhancement; (2) frequency-selective saturation pulse proton density and T2-weighted MRI is superior to proton density and T2-weighted conventional MRI; (3) frequency-selective saturation pulse MRI showed gadopentetate dimeglumine enhancement as well as proton density/T2-weighted signal aberration in exactly the same portion of the intraorbital optic nerve.

PACS mini refresher course. Network and ACR-NEMA protocols.

The backbone of the picture archiving and communication system (PACS) is the electronic network used to move information. Communications networks require electronic rules of operation or protocols so that a set of data being transmitted reaches the intended destination and does not collide with another set of transmitted data. The most efficient protocol is flexible and can respond to the fluctuations in volume of data transmitted via the network. Successful network connection of PACS devices requires standardized interfaces so that equipment from multiple vendors can use the network protocol. The American College of Radiology (ACR) and the National Electrical Manufacturers Association (NEMA) have developed a standard for imaging equipment interfaces: DICOM (Digital Imaging and Communications in Medicine). The DICOM standard allows interoperability among different computers and operating systems. It is flexible and will allow modification and expansions as new imaging techniques evolve. The authors and the ACR-NEMA committee believe that the DICOM standard represents an important choice for radiologists, since it was developed with their interests in mind.

Understanding and using teleradiology.

In 1972, Webber and his coauthors closed their landmark paper with some visionary remarks that have proved to be remarkably perceptive. They hypothesized that special telephone circuits or radiofrequency channels could be used to yield "images whose grey scale and resolution are satisfactory enough to be virtually indistinguishable from the original." Speaking of transmitting still-frame images in a reasonable length of time and at a reasonable cost, they were limited by the current state of technology, but not by failing to use available technology creatively. We now have the tools they lacked; we must analyze alternatives and apply them. First, define the clinical problem. Determine the minimum acceptable function level of the proposed teleradiology system. Then use your best judgement to sort our convenience, reliability, cost, and various other considerations in light of the needs of your practice. As you develop the scenario, frequently refocus on the problem to be solved. Very likely you will find, as you look closer at current options, that by using teleradiology you could increase the quality of service to your patients by extending your presence electronically to areas where constant physical presence is simply not possible, affordable, or convenient.