Interpretation of CT studies: single-screen workstation versus film alternator

Comparison of navigation techniques for large digital images

Medical images are examined on computer screens in a variety of contexts. Frequently, these images are larger than computer screens, and computer applications support different paradigms for user navigation of large images. The paper reports on a systematic investigation of what interaction techniques are the most effective for navigating images larger than the screen size for the purpose of detecting small image features. An experiment compares five different types of geometrically zoomable interaction techniques, each at two speeds (fast and slow update rates) for the task of finding a known feature in the image. There were statistically significant performance differences between several groupings of the techniques. The fast versions of the ArrowKey, Pointer, and ScrollBar performed the best. In general, techniques that enable both intuitive and systematic searching performed the best at the fast speed, while techniques that minimize the number of interactions with the image were more effective at the slow speed. Additionally, based on a postexperiment questionnaire and qualitative comparison, users expressed a clear preference for the Pointer technique, which allowed them to more freely and naturally interact with the image.

Thin-section CT of the lungs: Eye-tracking analysis of the visual approach to reading tiled and stacked display formats

OBJECTIVE

To use eye-tracking analysis to identify the differences in approach to and efficiency of reading thin-section CT of the lungs presented tiled and stacked soft-copy displays.

MATERIALS AND METHODS

Four chest radiologists read 16 thin-section CT examinations displayed in either a tiled (four images at once) or stacked (full screen cine) format. Eye-movements were recorded and analysed in terms of movement type; saccade distance (classified by the calculated range of useful peripheral vision), number of fixations, duration and direction of gaze-comparison of the areas of the images viewed.

RESULTS

Cases presented in stacked format were read quicker than when presented in tiled format with a greater fixation frequency (5 fixations versus 4.5 fixations points per 100 data points; p<0.001) and a greater proportion of short saccades (97% versus 94%; p<0.005). The consistency with which the observers viewed equivalent areas of the scan images in different cases was greater when viewing in stacked format (mean kappa 0.45 versus 0.36; p<0.05) suggesting a more systematic approach to reading.

CONCLUSION

Eye-tracking data demonstrates why thin-section CT examinations of the lungs are read more efficiently when displayed in a stack as opposed to a tiled format.

Multi-detector computed tomography and 3-dimensional imaging in a multi-vendor picture archiving and communications systems (PACS) environment

RATIONALE AND OBJECTIVES

To show the impact of the introduction of multi-detector computed tomography (CT) on radiologic workflow and to demonstrate how this reflects on picture archiving and communications systems (PACS) requirements.

MATERIALS AND METHODS

Production measurements were obtained from different CT scanners (first two single-slice CT scanners; from December 2001 single and 4-slice CT; from April 2002 single and 16-slice CT) in number of patients from the radiologic information system. Implications on our PACS were recorded in terms of images and studies stored. Furthermore, our PACS design was made so that optimal use of 3-dimensional imaging within the radiologic workflow was possible. Finally, the number of non-diagnosed studies were recorded every day since the start of the transition to a filmless radiology department.

RESULTS

This PACS design achieved a high level of integration between simple viewing and advanced 3-dimensional imaging and is optimized for handling large amounts of data. Overall increase of patients scanned with CT from January 2002-December 2003 was 54%. The number of series increased by 286% from December 2001-April 2003 and by 130% from April 2002-December 2003. From January 2002-February 2003, the number of images per patient increased from 175 to 450 (157%). Non-diagnosed studies decreased from about 100-120 before to practically zero after PACS implementation.

CONCLUSION

PACS significantly increases productivity because of availability of the images and elimination of certain manual tasks. These results show that although the amount of examinations increases significantly with the introduction of MDCT, simultaneous introduction of PACS and filmless operation allows radiologists to handle the growth in workload.

Soft copy display requirements for digital mammography

One of the advantages of digital mammography is to display mammograms on softcopy (electronic displays). Softcopy display of mammography is challenging because of the spatial and contrast resolution demands present in mammograms. We have designed and developed a softcopy mammography display application, Mammoview, which is capable of allowing radiologists to read mammograms as quickly and as accurately as they can on film alternators. We review the studies using Mammoview to elucidate the requirements of a successful softcopy display station. The design and development of the Mammoview softcopy display station are described in this article, and results of several studies using Mammoview are reported, including subjective feedback from Radiological Society of North America (RSNA) conference demonstrations, and clinical studies measuring performance in terms of speed and accuracy. Additional analysis of user interactions and user feedback is used to study the successes and shortcomings of mammography display stations like Mammoview. Overall, radiologist readings using Mammoview have been shown to be as fast and as accurate as readings using mammography film alternators. However, certain parts of the softcopy interface were more successful than their film counterparts, whereas others were less successful. Data analysis of the recorded human-computer interactions for the softcopy component of the clinical trial indicate statistically significant correlations between the difference in review time of softcopy versus alternator readings and three factors: the number of interactions, the reader, and the size of the image being reviewed. The first factor (number of interactions) suggests that simpler interfaces require less time to use; the second factor, the reader, supports previous findings that radiologists vary in how fast they read screening mammography studies; the third, size of image, suggests that the speed of softcopy review is increased relative to film readings when images are significantly larger than the display size. Feedback from radiologists using the system in clinical trials and at demonstration exhibits at RSNA indicated good acceptance of the interface and easy adaptation. Radiologists indicated that they felt comfortable using the interface, and that they would use such a softcopy interface in clinical practice. Finally, preliminary work suggests that the addition of a simple interaction to incorporate computer-aided detection (CAD) results would improve reading accuracy without significantly increasing reader times.

Accuracy of interpretation of CT scans: comparing PACS monitor displays and hard-copy images

OBJECTIVE

The purpose of this study was to determine the relative diagnostic accuracy of radiologists in the interpretation of CT scans using a computer workstation in comparison with using film.

MATERIALS AND METHODS

Four board-certified radiologists with extensive soft-copy experience interpreted 117 CT scans in four anatomic regions using films displayed on an alternator and images displayed on a four-monitor workstation. The radiologists were asked to interpret the scans in their usual fashion and were aware that both the time required to review the study and the accuracy of the reports were being assessed. The radiologists' diagnostic impressions were compared with those of a consensus panel and scored for accuracy.

RESULTS

Soft-copy interpretation using computer workstations was found to produce statistically significant improvement in combined measurements of sensitivity, specificity, and overall accuracy for chest, brain, and chest-abdominal CT scans compared with film interpretation.

CONCLUSION

PACS (picture archiving and communication system) offers radiologists the potential for improved accuracy in CT interpretation compared with traditional film-based interpretation.

Display method can affect interobserver agreement: comparison of ‘zoom-and-pan’ and ‘browse-and-paste’ for primary CT interpretation

Eight radiologists interpreted body CT images of 30 cases using a viewing station (six 17-in. monitors, 1024x1280). Using two different display methods, 'zoom-and-pan' and 'browse-and-paste', the readers described the presence or absence of liver tumors using a five-point rating scale and temporal changes between the current and previous studies using a seven-point rating scale. There was no significant difference in kappa values for tumor detection between the two display modes. However, in describing temporal changes, the kappa value of the browse-and-paste was significantly lower than that of zoom-and-pan (p<0.01). Browse-and-paste may have the disadvantage of greater interobserver variation.

Radiologists' productivity in the interpretation of CT scans: a comparison of PACS with conventional film

OBJECTIVE

We compared radiologists' times in the interpretation of CT using hardcopy films with the interpretation using a soft-copy picture archiving and communication system (PACS) computer workstation.

MATERIALS AND METHODS

One hundred CT examinations were selected at random and reviewed by four board-certified radiologists experienced in soft-copy interpretation. We performed time-motion analysis to determine the total time required to display, interpret, and dictate the individual findings of CT using conventional hard-copy interpretation on a viewbox and soft-copy interpretation, using a four-monitor high-resolution (2048 x 1536 pixel) workstation.

RESULTS

Time-motion analysis showed a reduction of 16.2% in the overall time required for soft-copy interpretation of CT compared with that of film. Time savings with soft-copy interpretation were observed for all four participating radiologists. The benefit of soft-copy interpretation was increased for examinations in which there were comparison studies.

CONCLUSION

We found that soft-copy interpretation of CT using a PACS workstation requires less time than interpretation using conventional film hung on a viewbox. The transition to filmless imaging has the potential to improve radiologists' productivity and report-turnaround time.

A picture archiving and communications system featuring multiple monitors using Windows98

We present an effective approach to manage, review, and distribute Digital Imaging and Communications in Medicine (DICOM) images with multiple monitors using Windows98 (Microsoft Corp, Redmond, WA) that can be implemented in an office-based setting. Computed tomography (CT), magnetic resonance imaging (MRI), and angiographic DICOM images were collected, compressed, and stored using Medweb (Medweb, Inc, San Francisco, CA) software. The Medweb server used the Linux/UNIX operating system on a Pentium 333-MHz processor with 128 MB of RAM. Short-term storage capacity was about 2 weeks with routine usage of an 11-GB hard drive. Images were presented for reading on a dual-monitor Windows98 Pentium display station with 160 MB of RAM using a Medweb/Netscape (Netscape Communications Corp, Mountain View, CA) viewer. There was no significant discrepancy in diagnosis between electronic and conventional film images. Mean reading time for 32 cases was 118 seconds. The Medweb JAVA plug-in viewer loaded the first image within 30 seconds of selecting the case for review. Full uncompressed 16-bit images allowed different window settings to better assess for pathology. Multiple monitors allowed viewing various hanging protocols. Cine viewing was also possible. Key diagnostic images were electronically transmitted to referring physicians. On-call radiologists were able to access images through the Internet. By combining Medweb, DICOM, and web-browser software using desktop personal computers (PCs), an easily accessible picture archiving and communications system (PACS) is available to radiologists and referring physicians. Multiple monitors are easily configured and managed using Windows98. This system can sustain changes and can be extended to provide variable functions using inexpensive PCs.

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.

Teleradiology: state of the art in clinical environment

Teleradiology may even be a tautology since communication is an essential part of radiology. The value of a radiological report is strictly dependent on how fast and clearly it is transmitted to the referring physician. The radiologist has therefore learnt to combine imaging expertise with communicator's skills. However, the term teleradiology is usually reserved to define the instances in which computers and digital networks help to reduce the limitations imposed by the physical distance between radiologists and between radiologist and referring physician. In this paper the main clinical applications of teleradiology will be presented, distinguishing between intra-institutional teleradiology (that involves more units belonging to the same department or to the same hospital) and inter-institutional teleradiology (more classically aimed at primary interpretation and subspecialty consultation). Finally a brief mention will be made concerning the potential for Internet to provide radiologists with new professional and educational opportunities.

Clinical evaluation of newly developed CRT viewing station: CT reading and observer's performance

The clinical performance of the new viewing station with six CRT monitors (17-inch, 1,024 x 1,280) was evaluated. In the primary interpretation of CT images, time measurements were carried out for eight radiologists. No significant differences in reading time existed between CRT and film in 3 of 4 readers in head CT series, and in 2 of 6 readers in body CT series. Compared with the previous system, the new prototype system achieved an approximately 30% decrease in reading time in both head and body CT studies and could reduce mental and eye fatigue.

Preliminary time-flow study: comparison of interpretation times between PACS workstations and films

Toshiba Hospital installed a PACS and RIS in the diagnostic imaging department along with a hospital-wide HIS in May 1993. Our PACS includes three diagnostic workstations each of which is provided with six monochrome CRT monitors. The diagnostic workstations have been used as the primary tools for interpretation of almost all radiographic images. The actual image interpretation time was measured for diagnostic workstations (237 examinations) and for conventional hard-copy films (219 examinations) for CR, CT, and MRI. The difference in interpretation times between diagnostic workstations and films was not significant. With regard to image interpretation time, diagnostic workstations are thought to be acceptable for practical image reading.

Digital chest radiography: clinical aspects

Technical development puts the completely digital radiology department within reach. Presently available systems have slightly inferior spatial resolution than film/screen systems. This is well compensated for by image processing. In the future, the digital radiology department working environment will be different. Systems should be designed that conform as much as possible to radiologists' present way of working to facilitate transition to the new system and avoid unnecessary stress.

Computed tomography interpretations with a low-cost workstation: a timing study

An ergonomically simple prototype workstation with two 900 x 1,100-pixel monitors capable of displaying eight full-resolution computed tomography (CT) images in 0.2 seconds, was compared with film for interpretation of computed tomographic images of the chest and abdomen. The hardware platform for this workstation cost less than $11,500 in 1993. A repeated-measures experiment was used to generate average interpretation times of 6.17 minutes for the workstation and 6.03 minutes for the film, including loading and unloading films, with three of the four subjects averaging about a minute longer for each workstation interpretation. All dictated reports were of clinically acceptable accuracy. All radiologists stated that workstations based on this design would be an acceptable clinical tool. However, observation suggested human working-memory strain among infrequent CT readers that could indicate the need for additional training. These data suggest that low-cost workstations can have practical application in interpretation of digital medical images such as CT, with the possibility of small increases in interpretation time.

How many screens does a CT workstation need?

A considerable number of prototype and commercial workstations have been developed during the last 10 years for electronic display of computed tomographic (CT) images during clinical interpretation. These CT workstations have varied widely in the number and size of monitors available for the display of the medical images ranging from a single 1,024 x 1,204-pixel monitor, to eight 2,500 x 2,000-pixel monitors. Image display times also have varied considerably, ranging from as fast as .11 seconds, to as slow as 26 seconds to fill a single monitor. No consensus has formed in the workstation community with regard to display area and response time requirements. To address this issue, we have constructed a time-motion model of CT interpretation. Model accuracy is experimentally verified with three workstations as well as with the film alternator. In general, CT interpretations with an electronic workstation become faster as display area increases and display time decreases. Results can be used by workstation designers and purchasers to roughly estimate differences in interpretation speeds among contending CT workstation designs.