Taming the Torrent of Multislice Images

Multislice CT scanners have become the core of the 21st century radiology department. Sixteen-slice scanners took the market by storm just a few years ago, proving their utility in a wide range of applications and becoming the new bread and butter of many radiology departments and imaging centers. The market has been equally welcoming to their 64-slice siblings, which offer improved speed and image resolution to make cardiac CT a reality. But no matter how the situation is sliced, these powerhorses present a major workflow challenge. That's because 64-slice scans can entail several thousand images; per image image size may be a hefty 0.5 megabyte. This mega-data is produced faster than ever before. Scan times have fallen to just a few seconds, but CIOs and department heads need to think long and hard to guarantee instant image access.

Healthcare facilities have employed a variety of mechanisms to master the multislice beast. First on the list may be changing reading protocols. "It's not feasible to trudge through 1,500 images axially," points out W. Daryle Heath, CT supervisor at St. Dominic Jackson Memorial Hospital in Jackson, Miss. Radiologists need to embrace a paradigm shift. "We aren't dealing with slices anymore. Sub-millimeter thick slices [are not meant to be examined individually]. They are sections of data that lead to clinically relevant images via post-processing. We need to move away from the term 'slice' and think about computerized volumetric imaging. CT has become more analogous to MR angiography with a volumetric acquisition and interrogation," explains Jay Cinnamon, MD, neuroradiologist and director of 3D imaging at Quantum Radiology Northwest in Marietta, Ga.

Many sites rely on highly trained techs for 3D scanning and post-processing. Quantum Radiology has employed a 3D lab model; specialized techs complete the lion's share of post-processing in a central area. Results are promising. CT angiogram post-processing that required an arduous 45 minutes to an hour two years ago has now been cut to a very reasonable 10 minutes.

And technology, in the form of dedicated 3D workstations and software or dedicated servers, can save the day as well. The ultimate technical solution will be a truly integrated 3D PACS model, predicts Matthew Barish, MD, director of 3D imaging processing center at Brigham and Women's Hospital in Boston. In this model, the PACS permanently stores thin-slice data for 3D reconstruction at any time in the future. This model requires easily accessible 3D hanging protocols and tools.

Ultimately, streamlined multislice workflow depends on a delicate balance between technology and organizational management. "Staff can learn the 'buttonology' to master new scanners and workstations, but organizational management is a big gap," says Cinnamon. In other words, facilities must determine processes and protocols that tame the multislice beast, allowing them to reap the full clinical gains without sacrificing workflow.

Moving into the future, CAD will play a larger role in CT workflow as new CAD software and reading paradigms help reduce the multislice workflow burden for screening studies.

Inside the 3D lab

Quantum Radiology Northwest typifies the busy outpatient imaging practice. It is equipped with more than a dozen CT scanners and serves three area hospitals. The CT portfolio includes a newly installed Philips Medical Systems Brilliance CT 40-slice scanner, three 16-slice scanners and Philips and Vital Images multimodality workstations. The practice plans to add a 64-slice scanner in 2006.

"Radiologists are viewing forty 4,000-slice studies each day," offers Cinnamon. "[Many] require post-processing. Practices have to deal with workflow. A centralized 3D post-processing lab is the way to go." Many advanced studies made possible by higher-slice scanners such as CT angiograms and lung nodule assessments require a post-processing step.

Quantum Radiology keeps post-processing time to a minimum by relying on specially trained techs to complete the bulk of the post-processing. The radiologist completes the post-processing, reviews and dictates the case. "It's like a relay race with the tech handing a baton to the radiologist. The challenge is that the baton hand-off occurs at different points for different applications," explains Cinnamon.

Take for example a neurovascular CT angiogram. The tech completes 90 percent of the work including processing, measuring, filming and uploading to PACS. The radiologist usually focuses on review and dictation with no post-processing duties.

Virtual colonography follows a different paradigm. The tech acts as a screener, looking for and flagging polyps, which translates into about 50 percent of the post-processing tasks. The radiologist continues post-processing and reviews the study including flags.

Quantum Radiology has developed application-specific worksheets to serve as a bridge between the tech and radiologist. Each worksheet shows how much post-processing was complete and where the tech left off. Currently, paper worksheets are hand-delivered or faxed to radiologists; however, Cinnamon expects to see similar worksheets integrated into CT software packages in the near future, a step that could aid workflow.

Elkhart General Hospital, a community hospital in Elkhart, Ill. that recently upgraded from a 16-slice CT to a Siemens Medical Solutions SOMATOM Sensation 64, uses a similar approach. The radiology department has established protocols to standardize CT images sent to PACS. The standard protocols not only aid workflow but also limit the impact on PACS, says Samir E. Patel, MD, vice chairman of radiology.


PACS impacts

A new PACS can make a difference in CT workflow, too. Elkhart General Hospital upgraded to a new McKesson Horizon Medical Imaging PACS after it deployed its 64-slice scanner. "This has significantly improved workflow for the radiologists and techs," confirms Patel. While the hospital's older PACS was taxed by multislice CT, the new system stores larger data volumes and readily generates thin-slice images. The CT scanner semi-automates coronal reformats (a.k.a. the ever-popular "surgeon's views") and sends all the reformats to PACS. The PACS stores thin image datasets, and radiologists or techs can launch the 3D application with one click at any PACS workstation, which eliminates the need for a separate workstation for studies like coronary CTs or CT angiograms.

The new system also features a live feed from the 64-slice CT scanner to a fifth PACS monitor. This Vitrea monitor lets the radiologist read while the study is in progress. The five-monitor configuration promotes rapid review and eliminates the need for techs to interrupt radiologists with questions about details like patient positioning.

Patel believes the hospital has effectively developed a multislice workflow solution. "We're able to accommodate a greater volume of patients in the same amount of time, and productivity and workflow have improved. The radiologist is now the rate limiting factor."

Manhattan Diagnostic Radiology in New York City found it needed to add a dedicated PACS when it deployed a Toshiba America Medical Systems Aquilion 64-slice CT scanner because archive space was depleted. The new Heart Imaging Technologies WebPAX helps, but may not offer a complete solution. "We don't save all of the images. We save the best series," explains Jeffrey Goldman, MD, director of cardiac CT and MR. "If we need to return to the original data for a future reconstruction, we can't because we don't have the raw data."

PACS isn't the only high-tech workflow facilitator at Manhattan Diagnostic Radiology. The practice beefed up its network and added new, faster switches, a T1 internet line and a fiber optic line between its two offices - all in a move to streamline multislice workflow.


The 3D workstation

The other factor in the equation is the 3D workstation, so say those in the know.

"We needed at least three workstations when we deployed 64-slice CT: one for me, one at the scanner and one for the post-processing tech," states Goldman. These third-party advanced visualization workstations offer some workflow relief.

Manhattan Diagnostic Radiology uses Vital Images Vitrea workstations for its 3D reconstruction. The three workstations are connected via an intranet, enabling users to push images and folders from one workstation to the next without physically moving to (and logging on to) a second computer.

Brigham and Women's Hospital's 3D Image Processing Center uses multiple 3D workstation solutions to post-process multislice CT data including Barco's Voxar 3D software as well Vital Images Vitrea 2, GE Advantage Workstation and Siemens Leonardo.

Barish outlines three options for managing multislice workflow. The first option is a thick-slice approach. It's possible to reduce the amount of data coming from the scanner, by acquiring slices at 0.5 millimeter resolution and sending 5 millimeter slices to PACS. The thick-slice approach; however, eliminates all of the benefits of multislice scanners and limits post-processing options, so most facilities have bypassed this option. A more common approach uses the hard drive of the 3D workstation as a temporary archive for thin-slice data. Post-processed images are sent to PACS, and the hard drive of the 3D workstation is deleted as it fills.

A true 3D PACS model improves on other solutions by completely integrating post-processing into the PACS workstation. Thin-slice data are stored on PACS for future post-processing. This option hinges on robust 3D tool kits completely integrated into PACS. "Most PACS have some form of 3D tools, but they aren't easily available," notes Barish. For example, one radiologist might prefer a 3D abdominal CT hanging protocol with five millimeter slices and 20 percent overlap. Another might opt for three millimeter slices.

Facilities can post-process multislice images on PACS workstations equipped with 3D image-processing tools and stand-alone CT workstations. The PACS workstation approach provides some 3D capabilities but the tools may not be easily or instantly accessible. On the upside, this approach does provide faster demonstration and communication to the referring physician. The modality workstation model requires radiologists to move back and forth between a CT workstation that lacks PACS tools like dictation to the PACS workstation.

"The Barco model integrates the 3D package into PACS and allows the radiologist to use the PACS workflow to generate 3D images. There is no need to separate from the PACS workstation or workflow to access the complete 3D toolkit," sums Barish. The current upsurge of partnerships between 3D and PACS vendors indicates the appeal of this approach. Barish predicts most vendors will employ this model in the future.

Manhattan Diagnostic Radiology has its eyes set on a slightly different future. The practice plans to phase-in a central server approach. Images will be pushed to a Vitrea server instead of the three workstations to eliminate redundancy and the workstation-to-workstation pushing that taxes the network. Vital Connect adds another workflow-boosting element; the technology allows users to view 3D images over the web from anywhere in the world.

In the meantime, advances in modality workstations are aiding workflow. St. Dominic Jackson Memorial Hospital uses GE's Xtream software in conjunction with GE's LightSpeed VCT 64. The software completes direct multi-planar reconstructions (MPR) on the fly. "Direct MPRs greatly increase throughput. The MPR is built automatically and sent to PACS by the time the patient is off the table," says Heath.


Staffing challenges

Sixty-four slice scanners nearly double the throughput potential of 16-slice imagers, which could present a significant drain on techs and radiologists. Calculating staff needs is a key component of the workflow equation.

Take for example Elkhart General Hospital. The community hospital completes about 2,300 CT studies monthly with its 64-slice scanner and a second 16-slice scanner. The workload includes routine studies of the head, chest and abdomen and CT angiograms. Upgrading to 64 slice has changed the business model at the community hospital. Overall, CT volume is increasing 10 percent annually, and the community hospital is performing new exams like coronary CTs. The revamped operations required staffing changes. The hospital rounded out the CT schedule to ensure 24/7 operations; the new schedule called for hiring two additional techs and a part-time technical assistant to staff the department. The 24/7 model frees up the 64-slice scanner during the day for complex procedures like CTAs.

Heath tackles the complex calculus of CT staffing, citing research equating one tech and a 16-slice scanner with 2.3 studies an hour. An additional tech increases throughput to 4.3 scans, and three techs can complete 5.5 scans. "Every time you add a tech to a scanner, you increase productivity," sums Heath.


Worlds collide: CAD and CT

CAD, which has been used most as a mammography solution, may soon pop up on the multislice radar. New CAD tools may aid in CT screening of the lung and colon - which is critical as current radiology manpower may not suffice for screening needs.

Some colon and lung CT CAD solutions provide the conventional CAD second-read and incorporate other workflow-enhancers such as automatic measuring and registration tools. "The ultimate aims of computer assisted diagnosis are to increase reader performance [sensitivity and specificity] while reducing interpretation time and thus improving workflow," notes David Burling, MD, radiologist with St. Mark's and Northwick Park Hospitals in London. Burling says significant workflow improvements require the use of CAD as a first reader with subsequent case review by the radiologist limited to the few candidate lesions highlighted by CAD.

Although the primary reader paradigm is not ready for prime time, vendors are making progress toward improved reader paradigms. Medicsight's ColonCAD software can be used as a concurrent reader, with CAD highlighting likely polyp or cancer candidates to the radiologist as he or she navigates through the colon. This model overcomes the workflow challenges presented by the second-read model. The second-read model requires the radiologist to read the study before CAD is applied, which can lengthen interpretation time and impede workflow.

CAD also holds potential outside of new reading paradigms as upcoming solutions target additional clinical applications like detection, characterization and mapping of liver metastases.


Conclusion

Multislice CT - particularly 64-slice CT - offers the potential for incredible clinical gains. The scanners also bring workflow challenges. Scans are ultra-fast and generate tremendous amounts of data. Facilities need to find the appropriate combination of technical solutions and workflow processes to maximize the potential of the new scanners. This entails assessing PACS infrastructure and 3D workflow models and solutions. In the future, CAD may play a greater role in CT workflow as next-generation CAD solutions could go beyond incorporation of workflow tools. The computer could become a primary reader in certain CT screening studies, which would truly revolutionize radiology and workflow.