Diagnostic efficacy of compressed digitized real-time sonography of uterine fibroids.

RATIONALE AND OBJECTIVES: The authors investigated the diagnostic efficacy of compression of real-time ultrasound (US) examinations. METHODS: Low- and high-compression recordings (9:1 and 15:1, respectively) of examinations were generated by using Joint Photographic Experts Group algorithms. Seven radiologists used a five-level response scale to answer questions about the presence, number, and location of focal fibroid tumors in 67 randomly sorted uterine examinations. The images were viewed after no, low, and high compression. Results were evaluated by using multipatient, multireader receiver operating characteristic jack-knife analysis. RESULTS: Given the reduction in the US digital video rates from 74 Mbit/sec for uncompressed images to 8 Mbit/sec for low compression and 4.7 Mbit/sec for high compression, there were no statistically significant differences in accuracy between the compression schemes. Confidence intervals suggested that the sample size was adequate. CONCLUSION: Compressed images with compression ratios of 9:1 and 15:1 were diagnostically equivalent to uncompressed images of uterine fibroid tumors.

Processes involved in reading imaging studies: workflow analysis and implications for workstation development.

Software development for imaging workstations has lagged behind hardware availability. To guide development and to analyze work flow involved in interpretation of cross-sectional imaging studies, we assessed the cognitive and physical processes. We observed the performance and interpretation of body computed tomography (CT) scans and recorded the events that occurred during this process. We studied work flow using a bottleneck analysis. Twenty-four of a total of 54 cases (44%) involved comparing the images with those of prior scans. Forty-seven of 54 scans (87%) were viewed using windows other than soft tissue, or compared with precontrast scans. In 46 cases (85%), the interpretation stopped to return to a previous level for review. Measurement of lesions was performed in 24 of 54 (44%) cases, and in 15 (63%) of these cases, measurements were taken of lesions on old studies for comparison. Interpretation was interrupted in 14 of 54 cases (26%) by referring clinicians desiring consultation. The work flow analysis showed film folder retrieval by the film room to be the bottleneck for interpretation by film. For picture archiving and communication system (PACS) reading, the CT examination itself proved to be the bottleneck. We conclude that workstations for CT interpretation should facilitate movement within scans, comparison with prior examinations, and measuring lesions on these scans. Workstation design should consider means of optimizing time currently not used between interpretation sessions, minimizing interruptions and providing more automated functions currently requiring physician interaction.

Large picture archiving and communication systems of the world--Part 2.

A survey of 82 institutions worldwide was done in 1995 to identify large picture archiving and communication systems (PACS) in clinical operation. A continuing strong trend toward the creation and operation of large PACS was identified. In the 15 months since the first such survey the number of clinical large PACS went from 13 to 23, almost a doubling in that short interval. New systems were added in Asia, Europe, and North America. A strong move to primary interpretation from soft copy was identified, and filmless radiology has become a reality. Workstations for interpretation reside mainly within radiology, but one-third of reporting PACS have more than 20 workstations outside of radiology. Fiber distributed data interface networks were the most numerous, but a variety of networks was reported to be in use. Replies on various display times showed surprisingly good, albeit diverse, speeds. The planned archive length of many systems was 60 months, with usually more than 1 year of data on-line. The main large archive and off-line storage media for these systems were optical disks and magneto-optical disks. Compression was not used before interpretation in most cases, but many systems used 2.5:1 compression for on-line, interpreted cases and 10:1 compression for longer-term archiving. A move to digital imaging and communication in medicine interface usage was identified.

Prevalence of deep venous thrombosis in the lower extremities of children in the intensive care unit.

PURPOSE: To determine the prevalence of lower extremity deep venous thrombosis (LE-DVT) in children who spent at least 72 h in the pediatric intensive care unit (ICU). MATERIALS AND METHODS: Children up to the age of 17 years who spent at least 72 h in the ICU underwent lower extremity venous ultrasound at the end of their stay. Prevalence range for the sample size was calculated with a confidence interval of 95%. RESULTS: Among 76 children who spent 3-141 days in the ICU, the prevalence of acute (and silent) DVT was 4% (confidence interval 0-9%). All three affected children had femoral venous catheters in that leg during their ICU stay (17 unaffected children also had catheters). CONCLUSION: Children in an ICU setting are at significantly lower risk for thrombosis than adults in the same setting.

Large picture archiving and communication systems of the world--Part 1.

This is the report of a worldwide survey of 82 institutions done to identify large scale picture archiving and communication systems (PACS) in clinical operation in 1995. This survey found a continuing strong trend toward the creation and operation of large PACS. In the 15 months since the first such survey, the number of clinical large PACS went from 13 to 23, almost a doubling in that short interval. New systems were added in Asia, Europe, and North America. A strong move to primary interpretation from soft copy was identified, and filmless radiology has become a reality.

Imaging system architectures for picture archiving and communication systems.

Picture archiving and communications systems (PACS) provide for the intraelectronic management of acquired digital image examination. Mini-PACS are image-management systems focused on specific applications. Computer architecture to be applied to radiology applications includes pipelining to improve the speed of the central processing unit, client and server architecture for distributed radiology applications, and image file servers. Image-compression algorithms provide increased digital storage and increased image transmission speeds. Throughput rates can be improved by identifying the bottlenecks.

Unobtrusive evaluation of mammographer's eye movements during diagnosis of mammograms.

The authors sought to evaluate the visual search patterns of mammographers to better understand the process by which a diagnosis is reached when mammographic images are viewed. An unobtrusive gaze tracking system was applied to track gaze direction and pupil size. Data were collected at 60 Hz and analyzed to evaluate how visual search patterns (location and duration of gaze dwells and pupil size changes) altered when mammograms were repeatedly displayed. Two tests were performed. In the first test, a mammographer was shown the same mammogram on two occasions, separated by a 1-year interval. The second test evaluated the visual search patterns of four mammographers during a 30-minute display period, in which four mammograms were shown a variable number of times. Analysis of the gaze dwell data demonstrated that, although general recognition of a mammogram can occur within 1 second, even though 1 year separated the two occasions when the image was shown, repeated display of a mammogram may result in changes in (a) the time taken to reach a diagnosis, (b) the length of gaze dwell, (c) the total number of correct and incorrect diagnoses, and (d) pupillary constriction. Results from these tests may yield important information about how mammographers view images and how this process can affect diagnostic accuracy.

Telemammography: implementation issues.

Telemammography has the potential to improve access to centralized expertise for the interpretation of breast imaging studies. Digital mammography has more demanding spatial resolution requirements than other forms of medical imaging because of the need to detect microcalcifications, the fine details of lesion margins, and subtle architectural distortion. The resolution requirements for mammography have important implications for image acquisition and display technologies. The large size of the resulting image data sets places significant demands on local and wide area networks as well as storage media. Image data compression will be particularly important for telemammography to help make systems practical and affordable. This article describes how existing technologies can be adapted to implement telemammography systems in the near future.

Unobtrusively tracking eye gaze direction and pupil diameter of mammographers.

RATIONALE AND OBJECTIVES: The visual process that radiologists use for diagnosis is incompletely understood. This study developed techniques to unobtrusively track direction and pupil diameter of radiologists reading a wide variety of films. We evaluated the eye gaze patterns of mammographic experts to gain knowledge that might improve the rate of early detection of breast cancer. METHODS: A video camera with a near-infrared light filter is pointed at the mammographic expert who is reading mammograms. The video images are analyzed in real time on a personal computer to detect eye gaze direction and pupil diameter. Two separate trials were used: 1) to demonstrate the system's speed and ability to work with mammograms (a brief test with one mammographer was used) and 2) four mammographic experts evaluated 14 mammograms. RESULTS: In the first trial, the system successfully tracked the eye gaze of a mammographer who quickly recognized the patient case, with the pupil diameter briefly increasing 40%, and then the gaze direction dwelling in an area of microcalcifications. In the second trial, 66% of the false-positive results for films with masses were associated with long eye gaze dwells, whereas 33% of the prolonged dwells for films with microcalcifications were associated with true-positive diagnoses. CONCLUSIONS: This near-infrared light system successfully tracked the eye gaze direction and pupil diameter of mammographic experts evaluating films. The association of long eye gaze dwells with diagnostic accuracy varied with the type of object being viewed. In films with masses, false-positive diagnoses were associated with long dwells. In films with microcalcifications, true-positive diagnoses were associated with long dwells.

Functionality of gray-scale display workstation hardware and software in clinical radiology.

This article examines the functional factors crucial for the successful conversion from film-based radiography to radiologic gray-scale display systems, including hardware architecture and software requirements, radiologic workstation operations, and a multilayered intelligent user interface. Radiologic workstation operations are logically decomposed into case preparation, case selection, case presentation, case interpretation, and documentation and presentation of the diagnosis. A multilayered software architecture for an adaptive, intelligent user interface is proposed: a hardware interface layer, an object-oriented layer, and a knowledge-based layer. The knowledge-based layer is composed of three elements: image presentation based on context-dependent models of diagnostic requirements, knowledge-based expert systems for assistance in diagnostic decision making, and computer-assisted diagnosis to alert the radiologist to potential lesions or abnormalities.

Modeling of analog film-file radiographic retrievals. A Markov chain.

RATIONALE AND OBJECTIVES: Existing retrieval models for radiology film libraries have not incorporated the influence of previous retrievals. A Markov chain model for the retrieval rates from an analog film library is proposed as a means of considering this effect. METHODS: A Markov chain model was developed for the retrieval rates of an analog film library. The Markov chain model required identification of the states of the Markov chain, the required one-step transition probabilities between states, and the initial state probabilities. RESULTS AND CONCLUSIONS: The results from the Markov chain model compared favorably with the 30-day measurements (25,775 retrievals), but a large enough sample to determine a statistical confidence level was not considered.

Teleconferencing for cost-effective sharing of radiology educational resources: potential and technical development.

To develop a cost-effective method of sharing educational resources, a dial-up teleconferencing network was implemented between three radiologic sites for a 30-day period of evaluation. By means of standard dial-up telephone channels, compressed video and audio signals displayed radiologic images, slides, and text, allowing residents and faculty from the three sites to participate in sight and sound interactions. Each of the three sites used compressed video/audio coder-decoders (codecs) conforming to the Consultative Committee on International Telegraphy and Telephony H.261 standard. Four video cameras were used at each site, and the audio was run in full duplex mode. A multipoint video bridge was used to broadcast codec output signals to the input lines of the other codecs. Our evaluation found audio quality to be suboptimal, but capable of being improved; diagnostic image quality was adequate when a video zoom mode was used; the digital-archive mode of the codec proved advantageous; the H.261 codec permitted participation from all sites; and all conference lecturers were able to conduct their conferences as they were accustomed. Although audio quality and spatial resolution need to be improved, the results of this pilot study imply that dial-up compressed video conferencing has the potential to become a practical, cost-effective method of sharing educational resources by means of interactive radiologic multisite educational programs.

Historical perspective on computer development and glossary of terms.

This article contains a concise history of the development of mechanical and electronic computers, descriptions of the milestones in software development, discussion of the introduction and adoption of computers in radiology, and a glossary of computer terms used frequently in radiology. One of the earliest devices designed to mechanize calculations was the calculating clock, built in 1623. The first programmable electronic computer, the ENIAC (electronic numerical integration and computer), was completed in 1945 at the University of Pennsylvania. Software has developed from early machine language through fourth-generation languages and graphic user interfaces used today. The computer was introduced to radiology initially in the 1960s in nuclear medicine and is now incorporated in many digital imaging modalities throughout radiology. The development of picture archiving and communication systems has resulted in the implementation of several totally digital departments of radiology.

Design of a high-speed, high-resolution teleradiology network.

A teleradiology system acquires radiographic images from one location and transmits them to one or more distant sites where they are displayed and/or converted to hard-copy film recordings. The long-term goal of teleradiology research is to show that teleradiology systems can provide diagnostically equivalent results when compared with conventional radiographic film interpretation. If this hypothesis is proven, provision of the following radiology services will be improved: (1) providing for primary interpretation of radiological images for patients in underserved areas as well as in other medical facilities; (2) integration of radiological services for multihospital/clinic health care provider consortiums; (3) improving emergency service and intensive care unit coverage; (4) offering consulting-at-a-distance with subspecialty radiologists; and (5) providing radiologists in the community or in rural areas with immediate access to large academic centers for help in the interpretation of difficult and problematic cases. We are designing a high-speed, high-resolution teleradiology network that will communicate between our level 3 medical center and several outlying medical centers within the metropolitan area. Computed tomography (CT), magnetic resonance (MR), and screen-film examinations will be digitized to 2,000 x 2,000 or 4,000 x 4,000 pixels at the remote sites, transmitted to the central referral facility, and sent to a laser film printer, replicating the original film. This film may then be used for primary diagnosis, overreading/consultative purposes, or for emergency department preparation. Inherently digital modality data (eg, MR and CT) can be sent without digitization of the multiformat film if desired.

Performance characteristics and image fidelity of gray-scale monitors.

Gray-scale monitors are an essential element of electronic radiology, and their ability to provide images that are perceived to be identical to those available on conventional or laser-printed film is crucial to success of electronic radiology. Image fidelity is measured in physical characteristics (luminance, dynamic range, distortion, resolution, and noise) and with psychophysical techniques, including receiver operator characteristics analysis with clinical images and testing with contrast-detail patterns to determine threshold contrast. Currently, laser-printed images facilitate greater information transfer than does a gray-scale monitor because of their higher absolute luminance (500 ft-L vs 60 ft-L), greater perceived dynamic range, and better spatial resolution. In the near future, the developments of gray-scale monitors with 150-200 ft-L luminance, a display standard based on just noticeable differences, and algorithms to improve similarities between gray-scale display images and laser-printed images will help increase the acceptability of monitors as a means to make primary diagnoses.

PACS mini refresher course. Wide area network strategies for teleradiology systems.

Teleradiology systems require the use of wide area networks (WANs). Design and implementation of a WAN depend on the number of images to be transmitted, desired digital image throughput (based on signaling rate), and cost of the communications link. Image transmission load must be estimated before the communications link can be selected. Communications links used in WANs include T-1 carrier point-to-point service, digital service (DS)-1 dial-up service, DS-3 point-to-point service, DS-0 dial-up service, digital microwave, fiberoptic local loop carriers, and metropolitan area networks (MANs). Depending on the distance between sites, T-1 service may be less costly than DS-1 service; however, for distances more than 200 miles, DS-1 service can be less expensive and more flexible. Both of these services and DS-0 service have lower signaling rates than DS-3 service, which is the fastest and most expensive link. Microwave and fiberoptic links are less expensive but have distance limitations of 14 and 30 miles, respectively. MANs are still being developed but hold the promise of higher signaling rates at lower costs.