Sridhar B. Seshadri

Magnetic Resonance Imaging Simulator: A Teaching Tool for Radiology

The increasing use of magnetic resonance imaging (MRI) as a clinical modality has put an enormous burden on medical institutions to cost effectively teach MRI scanning techniques to technologists and physicians. Since MRI scanner time is a scarce resource, it would be ideal if the teaching could be effectively performed off-line. In order to meet this goal, the radiology Department at the University of Pennsylvania has designed and developed a Magnetic Resonance Imaging Simulator. The simulator in its current implementation mimics the General Electric Signa (General Electric Magnetic Resonance Imaging System, Milwaukee, WI) scanner’s user interface for image acquisition. The design is general enough to be applied to other MRI scanners. One unique feature of the simulator is its incorporation of an image-synthesis module that permits the user to derive images for any arbitrary combination of pulsing parameters for spin-echo, gradient-echo, and inversion recovery pulse sequences. These images are computed in 5 seconds. The development platform chosen is a standard Apple Macintosh II (Apple Computer, Inc, Cupertino, CA) computer with no specialized hardware peripherals. The user interface is implemented in HyperCard (Apple Computer Inc, Cupertino, CA). All other software development including synthesis and display functions are implemented under the Macintosh Programmer’s Workshop ‘C’ environment. The scan parameters, demographics, and images are tracked using an Oracle (Oracle Corp. Redwood Shores, CA) data base. Images are currently stored on magnetic disk but could be stored on optical media with minimal effort.

The Digital Imaging Workstation

Picture archiving and communication systems (PACS) are expected to convert film-based radiology into a computer-based digital environment, with associated cost savings and improved physician communication. The digital workstation will be used by physicians to display these “soft-copy” images; however, difficult technical challenges must be met for the workstation to compete successfully with the familiar viewbox. Issues relating to image perception and the impact on physicians’ practice must be carefully considered. The spatial and contrast resolutions required vary according to imaging modality, type of procedure, and class of user. Rule-based software allows simple physician interaction and speeds image display. A consensus appears to be emerging concerning the requirements for the PACS workstation. Standards such as the American College of Radiology/National Electrical Manufacturers’ Association Digital Imaging and Communication Standard are facilitating commercial applications. Yet much careful study is needed before PACS workstations will be fully integrated into radiology departments.

Development Of A Physician-Friendly Digital Image Display Console

A high speed fiber optic network for the transmission of digital images has been under development for the last three years at our Hospital. This network utilizes a ring architecture with token passing contention handling. Radiographs are digitized with a high resolution camera. Images can be viewed at either high or low resolution. The software for this four node Medical Image Management System (MIMS) is now complete and is undergoing trial runs. Clinical tests begin on March 1, 1986. This paper will focus on the philosophy, evolution and the present state of the interfaces that exist between the system and the physician. Care has been taken to develop an interface that is fast, powerful and error-free. Though simple to use, it presents the physician with a number of powerful options to manipulate the image to facilitate effective interpretation. An effort has been made to incorporate those functions that are useful to the physician. We tried to avoid cluttering the user menu with an array of less-used options.

Clinical experience with PACS at the University of Pennsylvania

A Picture Archiving and Communication System (PACS) was installed in the Medical Intensive Care Unit of the Hospital of the University of Pennsylvania. For one year, 8 week periods of FILM ONLY usage were alternated with 8 week periods of PACS OR FILM usage. The time interval between obtaining portable chest images and taking image dependent actions decreased when the PACS was used, however, about 40% of the action decisions were made without a radiologists consultation. Only 5% of action decisions were made without consultation during the FILM ONLY periods. A new clinical study for measuring diagnostic accuracy and efficiency as well as communication patterns is described.

PACS at Penn

History: Our experience with Medical Image Management Systems (MIMS, also called PACS) began in 1982 with the creation of a digital subtraction angiography (DSA) unit. This DSA system was built utilizing a DeAnza image array processor with boards fabricated by our staff to interface with a Siemens angiography room. Because of the need to transmit and eventually store very large image files on a remote computer, we designed and fabricated a point-to-point fiber-optic link [82-ARENA. This device was later marketed by Canoga Systems and was an important contribution to the design of commercial fiber-optic networks. Recognizing the importance of a versatile Radiology Information System (RIS) and its critical inter-relationship to a MIMS, some very early work on RIS design was carried out [79-ARENA, [79.B-AREN ], [84-AREN ].

Design of a medical image management system: a practical cost-effective approach.

The impact of technology and economics is driving radiology departments into a digital era. There have been significant developments in the design of Medical Image Management System components. However, many important design criteria have been neglected, leading to an ineffective end product. This paper will discuss the more important design criteria. The design will be considered from the users point of view. The implementation of a prototype Medical Image Management System (MIMS) serving a Medical Intensive Care Unit in our Institution will be presented. The structure and very preliminary results of a clinical evaluation will be discussed. Plans to expand the MIMS beyond the Department and the Hospital will also be briefly discussed. The role of the personal computer in the design of a MIMS will be reviewed.

Folder management on a multimodality PACS display station

The Radiology Department at the University of Pennsylvania is installing a clinical picture archiving and communication system (PACS). The first phase of the PACS will support two MRI scanners, one film digitizer, and will provide display stations for four intensive care units and the MRI section. The software design for the image display stations has taken the form of two software modules: a display process (DP) and a worstation folder manager (WFM). This layered approach will ease the addition of new display stations into the PACS. The two processes communicate directly and through a folder database (FDB) that resides on the display node. The DP will allow the user to view and perform spatial and grayscale manipulation on multimodality images displayed on two high-resolution (2560 H X 2048 V) grayscale monitors. The WFM is responsible for processing folder requests from the DP, receiving folders from the main archive folder manager (MAIN_FM), fetching images from the image archive and retrieval system (IARS), and maintaining the FDB. All communication between the WFM and both the MAIN_FM and IARS is performed using ACR-NEMA style messages. The WFM has the ability to receive unsolicited folders in addition to folders on request. The WFM can also generate return folders for the MAIN_FM that contain physician reports of viewed images.

Assessing the impact of PACS on patient care in a medical intensive care unit

In this paper we have present data from pilot studies to estimate the impact on patient care of an intensive care unit display station. The data were collected during two separate one-month periods in 1992. We compared these two different periods in terms of the relative speeds with which images were first viewed by MICU physicians. First, we found that images for routine chest radiographs (CXRs) are viewed by a greater number of physicians and slightly sooner with the PACS display station operating in the MICU than when it is not. Thus, for routine exams, PACS provide the potential for shortening of time intervals between exam completions and image-based clinical actions. A second finding is that the use of the display station for viewing non-routine CXRs is strongly influenced by the speed with which films are digitized. Hence, if film digitization is not rapid, the presence of a MICU display station is unlikely to contribute to a shortening of time intervals between exam completions and image-based clinical actions. This finding supports the use of computed radiography for CXRs in an intensive care unit.

Prototype Medical Image Management System (MIMS) at the University of Pennsylvania: Software Design Considerations

A 10 Mbits/second fiber-optic network for the transmission of chest x-ray images has been designed and implemented at our Hospital. Images are acquired with a high-resolution laser scanner. The viewing consoles display images at spatial resolutions of either 512 square or 1024 square. User interfaces have been designed to simplify the digitization and display processes. The applications level networking software and all the image processing software has been developed in-house. The system is now serving a 11-bed critical care facility on a day-to-day basis. This paper will focus on the software design issues. The software will be presented from a systems perspective. The importance of the user in the design process will be stressed and exemplified. The role of intelligent, rule-based software will be demonstrated. Selected clinical results will be discussed.

On-demand retrieval paradigm

The University of Pennsylvania Medical Center has been operating a prototype clinical PACS for a number of years. The details of this implementation have been described elsewhere. Early on in the design phase we realized the need to pre-fetch images on a PACS network and incorporated rule-based pre-fetch mechanisms into our Folder Manager software suite. As our PACS expanded and as the pool of users increased to include MR technologies and researchers in addition to radiologists, the case for an on-demand retrieval mechanism became compelling. The design of such a paradigm posed special problems in that the system had to be robust and user-friendly. This paper discusses the design and implementation of such a system. Usage statistics collected over a one-year period are also presented. The retrieval profile shows certain patterns that can be exploited to improve the design of the PACS.