DOI: 10.1148/rg.231025088
(Radiographics. 2003;23:267-272.)
© RSNA, 2003
Use of Personal Digital Assistants for Retrieval of Medical Images and Data on High-Resolution Flat Panel Displays1
Osman Ratib, MD, PhD,
J. Michael McCoy, MD,
D. Ric McGill, BSRT,
Minglin Li and
Allen Brown
1 From the Department of Radiology, UCLA School of Medicine, 10833 Le Conte Ave, Los Angeles, CA 90095 (O.R., J.M.M., R.M.); CEDARA Software Corporation, Mississauga, Ontario, Canada (M.L.); and DOME Imaging Systems, Waltham, Mass (A.B.). Recipient of a Certificate of Merit award for an infoRAD exhibit at the 2001 RSNA scientific assembly. Received May 1, 2002; revision requested June 20; final revision received October 4; accepted October 10. Address correspondence to O.R. (e-mail: oratib@mednet.ucla.edu).
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Abstract
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For its new acute care hospital, the University of California at Los Angeles is evaluating innovative technology involving high-resolution flat panel display devices configured as "network appliances" that can be wall mounted for use in the retrieval and display of medical images and data. Physicians and healthcare providers can log on with wireless handheld computers, which can serve as an identification device as well as a navigational tool for selecting patient records and data. These data are displayed and manipulated on the flat panel display without the need for a keyboard or mouse. A prototype was developed with commercially available image display software, which was modified to allow the remote control of software functions from a handheld device through an infrared communication port. The system also allows navigation through the patient data in a World Wide Web–based electronic patient record. This prototype illustrates the evolution of radiologic facilities toward "shareable" high-quality display devices that allow more convenient and cost-effective access to medical images and related data in complex clinical environments, resulting in a paradigm shift in data navigation and accessibility.
© RSNA, 2003
Index Terms: Computers, diagnostic aid • Computers, multimedia • Picture archiving and communication system (PACS) • Radiology and radiologists, design of radiological facilities
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Introduction
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Recently developed handheld devices and personal digital assistants (PDAs) have significantly penetrated the general consumer market and have changed the way data and information are being exchanged and stored. The portability of handheld devices is particularly suitable for physicians and healthcare providers, "nomad" professionals who need access to data and information in multiple locations while providing patient care or engaging in academic or research-related activities (1,2). Thus, it is not surprising that the use of PDAs is becoming widespread among physicians, who rely on these handheld devices to make valuable information available in daily practice (3). Numerous systems have been developed to allow extracts from electronic patient records to be downloaded and stored on PDAs for ready access (4,5). In the future, wireless communication will provide the added convenience of direct access to central data repositories and sources of online information (1,2,6). Ever since PDAs became capable of displaying gray-scale or color images, users and software developers have been attempting to download and display medical images on these portable handheld devices (7–9). Recent reports have described a variety of clinical applications for handheld devices involving electronic medical records, including the display of medical images on the low-resolution screens of these devices (10,11). In some instances, the ability to access key medical images can be critical for patient treatment and therapeutic decisions, even if these images are displayed at relatively low resolution (12–16).
Our experience with using handheld devices to display medical images indicates that currently available handheld devices have three major limitations: low display resolution, low storage capacity, and relatively limited communication speed. These technical limitations restrict the use of handheld devices for accessing medical images in routine clinical practice. Larger devices such as digital "tablets" are emerging as an alternative, providing higher display resolution and larger storage capacity; however, they are less convenient to carry around and do not easily fit into one’s pocket.
In an effort to find an alternative solution that would combine the convenience of a handheld device with the high quality and performance of high-resolution image display systems, we developed an innovative system for image retrieval and display in the clinical setting. The system replaces existing light boxes with high-resolution wall-mounted flat panel displays driven by handheld PDAs that can initiate the query and retrieval of specific medical images and documents from remote storage archives (Fig 1). In this article, we discuss the materials and methods we used to develop our system, the results of its use, and the advantages and limitations of both currently available and yet-future systems for image retrieval and display.
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Figure 1. Photograph illustrates a possible implementation of a wall-mounted flat panel display in a clinical ward instead of a traditional light box. The display is driven by a handheld pocket personal computer (PC).
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Materials and Methods
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We developed a prototype that made use of a generic Windows Pocket PC handheld device manufactured by Compaq (Houston, Tex) and was also tested with alternative devices from other vendors such as Casio (Dover, NJ) and Hewlett Packard (Palo Alto, Calif). The device is based on the Pocket PC operating system (Windows CE) from Microsoft (Redmond, Wash). Both the prototype software components for the image display program and the Pocket PC module for exchanging patient lists and driving the flat panel display were developed by CEDARA Software (Mississauga, Ontario, Canada). The display software is a modified version of CEDARA’s standard picture archiving and communication system (PACS) diagnostic workstation software. The display software supports all Digital Imaging and Communications in Medicine (DICOM)–compliant modalities and offers a number of image presentation and image processing tools that are usually required for review and interpretation of radiologic images. Because the software is implemented on a Windows NT or Windows 2000 platform, it is easily adaptable to any single- or multimonitor display configuration with a wide range of display resolutions. Therefore, the software was also easily adaptable to the flat panel display used in our project. The flat panel display (Dome Technologies, Waltham, Mass) is a high-brightness, high-definition, 3-megapixel monitor in portrait mode with a 1,600 x 2,048 pixel resolution. The monitor is driven by a dedicated digital video board that is capable of handling gray-scale images with a dynamic range of 10 bits (1,024 gray-scale levels). The prototype that we developed includes a separate computer that hosts the software and the hardware necessary to drive the flat panel display. However, we anticipate that on more advanced prototypes the computer component could be mounted directly behind the monitor.
The software program was adapted and divided into two components. The first component consisted of the patient-study lists residing on the handheld device. The second component consisted of the complete image viewing and image manipulation program residing on the computer driving the flat panel display. The image viewing software also included all the necessary functions for retrieval and reception of images from any DICOM source or PACS archive. A special extension was added to the software to allow the handheld device to initiate communication with the viewing software. The communication between the two systems takes place through an infrared communication port. After the initial "handshaking" protocol, the software downloads an updated list of patients and studies available to that particular user. The list then appears on the handheld device, and the user can select the study to be displayed. Once the relevant images are displayed, their setting and display layout can be manipulated with a touch pad attached to the flat panel display (Fig 2). This touch pad is a commercially available pointing device that works just like the touch-sensitive pads on most laptop computers. It is connected to the computer by means of a standard Universal Serial Bus (USB) interface and does not require any additional software or hardware development.
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Figure 2. Photograph illustrates a typical setting in which a handheld pocket PC (1) communicates with a flat panel display (2) through an infrared communication channel (3). An additional touch pad pointing device (4) is mounted next to the monitor for manual image adjustment and display functions.
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The images were retrieved from our PACS archive server with a DICOM query-retrieve protocol embedded in the CEDARA software for diagnostic workstations. The images can also be preloaded on the local storage disk of the workstation with use of prefetching and routing algorithms or simply by means of manual selection and transfer. Retrieved images will remain in the local storage cache of the workstation for a period of time that varies depending on disk capacity and the volume of images retrieved. The system automatically manages the number of images that will be maintained on the cache disk, which depends on how long the image files resided on the workstation and how recently they were accessed. When the volume of images reaches a certain capacity, older images are automatically deleted from the local cache to provide additional space for incoming new studies.
The system relies on the handheld device to initiate a session, and user identification is obtained from the handheld device itself. Once a session is established through a first message exchange between the two systems, a list of available studies is automatically downloaded to the handheld device. This list can represent all the images that are currently available on the local storage disk of the computer driving the flat panel display, or it can be "filtered" to include only the patient records and studies that are relevant for that particular user. This work list will appear on the screen of the handheld device and is used to select the images to be displayed on the flat panel display. At any time, the user can also request that the corresponding diagnostic radiology report be downloaded to the handheld device for review (Fig 3).
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Results
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We developed this system as a pilot project to explore different alternatives for the distribution of medical images in clinical wards as part of the planning phase of a new filmless hospital being constructed at the University of California at Los Angeles. The project allowed us to explore and evaluate the advantages and limitations of this alternative method of image distribution. The results indicate that the technology of high-resolution flat panel display is adequate for displaying images in clinical wards under noncontrollable lighting conditions. Flat panel displays offer the convenience of easy wall mounting without the need for the extra counter or desk space that conventional monitors require. The use of a handheld PDA eliminates the need for a keyboard and pointing device. However, in our implementation, which made use of an infrared communication interface between the PDA and the computer driving the flat panel display, we were unable to achieve adequate interactive communication with use of the PDA as a pointing device for moving a cursor or adjusting image settings. The responsiveness of the system was too slow to provide adequate interaction in functions that require continuous motion tracking such as zoom and panning or adjustment of image contrast. This shortcoming required that an additional pointing device be added to our system: a small, touch-sensitive pad mounted next to the display monitor (Fig 2). The touch pad was incorporated only as a temporary solution to the problem of suboptimal communication between the PDA and the computer. Another alternative solution was to modify the flat panel display by adding a touch-sensitive layer, allowing the user to directly select specific graphic icons on the screen to perform specific functions. This alternative is significantly more expensive and was not recommended by the display manufacturer. A touch-sensitive screen would degrade the quality of the display and add significant glare as well as potential interference caused by fingerprints left on the screen by users. Furthermore, it would require modifications of the graphical user interface to allow the use of larger icons and control buttons that could be manipulated with finger pointing and dragging. Our solution—a touch pad acting as a conventional mouse—is compatible with most image display software used on conventional workstations and requires no modification. The availability of this additional pointing device also facilitates the use of other software programs that were not modified so as to be driven by the handheld device. Thus, it was easy to use the same wall-mounted display to navigate through existing World Wide Web–based patient records available at our institution. Ultimately, for the final design of such a hybrid system, we plan to incorporate a more efficient wireless communication network between the PDA and flat panel display software, allowing a PDA with a touch-sensitive screen to act as a pointing device. An attractive alternative that we are currently evaluating is based on the new short-range wireless communication standard—"blue tooth" technology—that is becoming more widely available in the electronics industry. Newer PDAs are already equipped with this technology.
Our prototype implementation was developed for a PDA based on the Microsoft Pocket PC operating system. However, most physicians tend to use Palm OS–based PDAs, and a large portion of the PDA market is held by Palm OS–based devices. The components developed for retrieval of study lists and data were carefully partitioned into small software components that can easily be migrated to the Palm OS platform. A prototype of a Palm OS–based implementation was tested to trigger the communication of data between the flat panel display software and the PDA, but a full implementation was not completed as part of the project. It is anticipated that for full clinical implementation, compatibility with different PDA systems will be required.
Our system relied on an infrared communication port that is readily available on handheld devices and is supported by most computer systems as a standard serial communication port. However, infrared communication suffers from limited range and the absolute necessity of having the two communicating devices aligned. Communication can easily be interrupted if the user moves the handheld device away from the direct line of communication between the receiving and emitting ports. Radio-frequency wireless communication networks could provide a more convenient alternative but are more complex and usually require additional security and encryption features that infrared communication does not require due to the very short range of data communication. Wireless local area networks carrying sensitive data require encryption and the use of a virtual private network to ensure the security and confidentiality of medical data. These requirements add a layer of complexity to the communication between handheld devices and the local area network but can easily be added to existing devices (17). We have already tested a virtual private network–based secure wireless communication network that is compatible with most handheld devices. We anticipate that the short-distance, low-power wireless communication protocols (eg, blue tooth technology) that are rapidly being developed will be superior to the infrared technology and will provide faster, more consistent communication between the handheld device and the computer driving the flat panel display, thereby allowing a PDA with a touch screen to act as a pointing device. Our prototype demonstrates only the feasibility of the system and could probably be improved for a final implementation.
Our prototype makes use of a standard PACS configuration in which images can be retrieved from a central archive server and stored locally for display. Thus, performance of this system in retrieving images is identical to that of any diagnostic workstation in our department. Images already stored locally can be displayed instantaneously, whereas retrieval of images from the central archive server will entail a delay as image files are transmitted to the local workstation. This delay can vary from a few seconds to about 1 minute depending on the size of the image file being retrieved and emphasizes the importance of prefetching algorithms and routing rules in a traditional PACS environment, in which images must be retrieved locally before they can be displayed. In a clinical setting, the computer driving the flat panel display must be preloaded with images from all patients in the area where the display system is located. An alternative, based on more recent PACS architectures that allow faster and more efficient data streaming from central servers, would make it possible to view images very rapidly with intelligent progressive transmission and display algorithms that do not require the full image data set to be transmitted to the local workstation before the images can be displayed.
Our system was presented to hospital physicians and attending clinicians and was exhibited at international conferences to gather user input and to evaluate its applicability in clinical settings. Users were generally enthusiastic, and all affirmed that the system would have great value in busy clinical environments in which traditional workstations are usually not practical. The general consensus was that display devices should be installed by patients’ beds. The most commonly heard suggestions were as follows:
- More of the image manipulation and navigation functions should be imbedded in the handheld device, so that user interaction with a separate touch pad attached to the flat panel display would be needed only for the basic image adjustment and display functions.
- Users should be able to select a subset of key images from those shown on the flat panel display to be downloaded to the handheld device.
- Greater integration of the other components of the electronic patient record is needed (the prototype system allowed access to only the images and corresponding diagnostic report).
In addition, we evaluated the ability of the same display system to display patient medical records retrieved from our enterprise Web-based electronic patient records. We used a touch pad attached to the flat panel display rather than a handheld device for all navigation and browsing functions. Therefore, we did not present that feature to users at this early stage.
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Discussion
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Our system was inspired by similar digital devices (often referred to as "network appliances" or "Internet appliances") that are emerging in the consumer market. A variety of systems are available that allow users to connect a digital display device to an Internet service to download images sent by relatives or friends. Unlike PCs, these devices have limited functionality and allow only specific display functions to be performed. Our project was also driven by the need to replace traditional workstations with a more practical way of retrieving and displaying images and associated data in busy clinical environments. One of today’s biggest challenges is providing information and data to healthcare providers in an efficient, convenient manner that leads to higher productivity and better patient care (7,13,16).
Our prototype enabled us to demonstrate the feasibility and evaluate the usefulness of combining handheld technology with a high-definition flat panel display system for retrieving and displaying medical images. We anticipate—and our survey results seem to confirm—that such a protocol would have significant additional value if it could display all the relevant components of the electronic patient record along with the medical images. Although it could be argued that a PDA would be unnecessary if wall-mounted flat panel displays were driven by conventional keyboards and a touch pad or a mouse, the greater convenience and lower space requirements of a PDA-driven system are attractive. The optimal hybrid solution could take advantage of two key features of a PDA-driven system: the mobility and convenience of a handheld device and the high definition and performance of a flat panel display system. Ideally, all the basic components of a patient’s medical record should be accessible through the handheld device, whereas the flat panel display could be used to display images and data at higher resolution. This hybrid solution would overcome the limitations imposed by handheld devices and would provide an attractive alternative to larger digital tablets, which offer higher-resolution display but are less portable. Because physicians and medical professionals seem to value the portability of a device more than its display resolution, it is foreseeable that a handheld device that can access and store large quantities of data will be preferred to larger devices with higher-resolution display. The market trend is toward smaller, lighter devices with higher storage capacity and better display definition. We anticipate that with the increased use of small but powerful pocket devices, the need for traditional computer devices with higher-resolution display will decrease (14–16). Wall-mounted display devices that are available in multiple locations in clinical wards and in patients’ rooms are ideal for users who do not require long interactions with such devices, but instead rely on their pocket devices in most of their work. These flat panel displays could become multipurpose shareable devices that different categories of users, including nurses or even patients, could use for different purposes.
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Footnotes
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Abbreviations: DICOM = Digital Imaging and Communications in Medicine,
PACS = picture archiving and communication system,
PC = personal computer,
PDA = personal digital assistant
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Abstract
Introduction
