Radiology Informatics

Hospital Information System and Electronic Medical Record

A medical imaging study begins with a patient-physician encounter that generates an order or prescription. From within a healthcare enterprise, patient demographic and medical data are collected and distributed by a HIS, which may or may not be completely computerized and paperless. An EMR is such a data system that is completely paperless. In an EMR environment, the imaging study can be ordered by clinicians via computer. Such a computerized physician order entry carries the potential advantages of providing relevant patient history and providing point-of-need decision support, such as image exam appropriateness criteria.

Radiology Information Systems

Regardless of the method of study order, radiology study orders must be communicated to a RIS. A RIS is a computer application that manages patient demographic data and scheduling and tracks associated images and reporting results. Once an imaging study order is entered into a RIS, the study is associated with a unique identifier code such as an accession number. The accession number and medical record number allow unambiguous association of the image dataset with the correct patient demographics; this also allows coordination of the patient’s scheduling and imaging encounter at the imaging modality. This system enables a patient study to be accessed at any site of a radiology department network for acquisition and communication of results and images back to the HIS/EMR. In addition, many of the business/operational analytics (scorecards, dashboards, and reports) necessary to monitor operational quality/efficiency are generated by the RIS or depend on RIS data.

Picture Archiving and Communication Systems

The RIS organizes patient data regarding a study but does not include the images themselves. The PACS is the information technology architecture that orchestrates the workflow of image acquisition, display, and storage across a network. Modern PACSs have largely replaced the need for hard copy film creation and transportation. The PACS also allows for quality improvement initiatives through additional software programs. PACSs have four main components:

• 1.

  The imaging modalities (radiography, computed tomography [CT], magnetic resonance imaging [MRI], ultrasound, etc.)

• 2.

  A secure transmission network

• 3.

  Computer workstations for viewing and manipulating images

• 4.

  Digital archives for storing images and reports for later retrieval

Ideally, one PACS serves all of the imaging modalities across an institution’s radiology services. Once imaging modalities acquire images scheduled by the RIS, image data is sent to the PACS database server. PACS servers typically communicate through a local area network (LAN) to various workstations, where images can be reviewed by radiologists, technologists, or caregivers throughout a health network. Networks, as well as digital archives, must maintain the security of patient data according to the regulations defined by the Health Insurance Portability and Accountability Act. A LAN maintains relatively high privacy as all computers on a network are physically wired to servers within a protective enterprise firewall. Large healthcare centers with multiple hospitals may have several LANs that intercommunicate and comprise a wide area network. In contrast, radiologists or caregivers may want to view images from outside a LAN, such as logging in through the Internet from home. In this case, a virtual private network (VPN) can be created. A VPN connects to the LAN with a comparable level of security to allow access to the PACS or EMR from outside the wired network.

PACS database servers send patient imaging studies to computer workstations for healthcare worker use and to archival storage. At larger institutions, storage servers can be maintained off-site at dedicated data centers. Archival storage must be secure, scalable, and have redundancy or backup. The performance of storage servers is dependent on the media technology used; however, the decreasing cost of magnetic spinning disc drives has allowed for its use to become preferred and commonplace. Current and near future enterprise requirements have driven the need for a scalable enterprise image/multimedia archive and image consumption architecture. Examples include the vendor-neutral archive, archive-neutral PACS vendors, and PACS-neutral archives.

PACS software packages include the radiologist’s tools for effectively and rapidly interpreting images. Preset window and level settings and hanging protocols are customizable for end users to fit individual personal preferences. Measurement tools, zoom, pan, and window adjustment are a few of the many assessment features needed. PACSs must also display patient information and prior studies, and their reports must be available. Modern offerings go beyond simple image study presentation and navigation and attempt to support more complex radiology workflow orchestration (e.g., real-time decision support, advanced visualization, advanced communication/collaboration, analytics, peer review).

Radiology Information Systems: Picture Archiving and Communication Systems Integration

There is clearly a need for RIS and PACS to communicate efficiently. Some vendors offer hybrid products comprising both RIS and PACS; however, that is not always the case. In scenarios where health networks work with different vendors, the radiologists’ workflow is derived by either the RIS or the PACS as the primary source of truth . A RIS-driven workflow seems intuitive based on having patient and study information and being the primary tool for schedulers and technologists. However, a PACS-driven workflow would use the imaging studies themselves to drive a worklist and would be within the software workspace that radiologists mainly use, acquiring additional data from the RIS via the accession number or other identifier. Regardless of the method used, optimized and localized integration of RIS-PACS to offer efficient workflows for both radiologists and technologists is vital for a reliable and accurate department system.

Health Level 7

Healthcare networks have many components in an information system, including the EMR, RIS, order entry systems, laboratory information systems, etc. Health Level 7 (HL7) is the computer standard governing the communication of these various information systems within and between healthcare networks. HL7 is responsible for communicating with a RIS and sharing information with an EMR. In imaging, this encompasses study ordering, registration, and results communication. HL7 characterizes each interaction as an event and can disseminate the associated message electronically to other systems.

Digital Imaging and Communications in Medicine

Although HL7 is the standard spanning the breadth of healthcare, Digital Imaging and Communications in Medicine (DICOM) is the technical standard for display, storage, and transmission of medical images. DICOM began as a collaborative effort by the American College of Radiology (ACR) and National Electrical Manufacturers Association in the early 1980s and was renamed DICOM in 1993. Now it has become the universal standard data format for images and communications among all medical imaging devices and software applications. A DICOM image also contains information regulated by the standard: media display, security profiles, data storage, and data encoding and exchange.

DICOM has been the critical enabler for interoperability of hardware and software spanning all aspects of radiology workflow (image acquisition modalities, PACS servers, workstations, networks). DICOM also allows image databases to be shared as PACSs develop and expand and maintain communication with other information systems.

DICOM does not have a centralized body to certify or enforce implementation of the standard. It is up to various vendors to conform to the standard. Although the standard can be followed, the mechanisms of use are not specified. Vendors almost universally provide DICOM conformance statements that explicitly state how a specific vendor’s offering supports DICOM. Also, vendors may opt to carry additional proprietary technical parameters, which may impact interoperability.

Integrating the Healthcare Enterprise

Despite the presence of HL7 and DICOM standards, there are still variations in interconnectivity and efficiency. An initiative called Integrating the Healthcare Enterprise (IHE) began in 1998 with a goal to improve the communication of different standards. IHE does not create its own standard but instead promotes the coordinated and best practice use of established standards. IHE identifies common system integration challenges requiring HL7-DICOM or other communication and creates an IHE profile of an expected technical workflow that can consistently deliver expected results. IHE initiatives grow in parallel to updates from HL7 and DICOM, and compliance can further increase an accurate and efficient workflow.

Image Data Compression

Image data can be electronically compressed into smaller files by mathematical algorithms, with a goal of decreasing storage needs and image transfer time. Image compression can be lossless, which is reversible, or lossy, which is irreversible.

Lossless image data storage is used by many PACS systems and removes any doubt regarding potential loss in diagnostic quality of medical images. Lossless compression involves removing redundant data, and a commonly known example file is the Graphics Interchange Format. The degree of compression is limited, however, and is typically in the range of 1.5:1 to 3:1.

Lossy image compression methods remove potentially relevant pixel data from image files. The compression ratio improves to greater than 10:1. Joint Photographic Experts Group (JPEG) uses lossy image compression and is widely applied in digital photography, with minimal impact on image quality. JPEG is also supported by the DICOM standard. Studies have shown that some lossy image compression techniques can be used effectively in medical imaging without an impact on diagnostic relevance.

Lossy image compression that does not affect a particular diagnostic task is referred to as diagnostically acceptable irreversible compression. The ACR does not have a general advisory statement on the type or amount of irreversible compression to be used to achieve diagnostically acceptable irreversible compression, and only methods defined and supported by the DICOM standard should be used, such as JPEG, JPEG-2000, or Moving Picture Experts Group. In addition, the US Food and Drug Administration (FDA) requires that images with lossy compression are labeled, including the compression ratio and method used. The FDA prohibits the use of lossy compression of digital mammograms for interpretation, although lossy compression can be used for prior comparison studies.