Integration of CAD with PACS breaks down barrier to its use

July 1, 2009

Computer-aided detection, now commonly used for nodule detection, is becoming more integrated with PACS, a trend that streamlines workflow.

Computer-aided detection, now commonly used for nodule detection, is becoming more integrated with PACS, a trend that streamlines workflow. The idea of integrating the two systems is gaining more widespread use as facilities try to maximize the potential that coordinating the processes can achieve, giving radiologists the ability to refer to CAD images during interpretation.

The lack of integration between PACS and CAD has been the biggest barrier to the use of CAD technology, according to Dr. Heber M. MacMahon, director of thoracic imaging at the University of Chicago Medical Center, a hub of CAD development.

"[CAD technologies] have not been tightly integrated into PACs, so it takes a lot of time to evaluate," MacMahon said. "If it takes more than a few minutes to bring up the interface and extract results, people won't use it in their practice because of the pressure to read large amounts of scans."

CAD and PACS developers have worked together to improve the software so that nodule detection can be done more quickly and reliably, he said.

Japanese researchers at Kyushu University hospital have integrated a server used for moving temporal-subtraction and nodule-detection images into PACS, allowing current and prior CAD images to be automatically loaded on display terminals, according to a report outlining their four-year experiment (J Digit Imaging 2008;21[1]:91-98).

The image-loading technique can easily be applied to other CAD systems, such as those for mammography, gastrointestinal exams, and CT, said Dr. Shuji Sakai, an associate professor of radiology at the university's school of medicine.

The report, however, did mention several problems associated with the integration process, including excessive false positives, difficulties with image orientation, and low image quality when temporal subtraction was performed on images obtained on different devices.

CAD software can be included in a stand-alone CAD workstation or be integrated in the PACS as PACS-based CAD.

In a report given at EuroPACS 2006, H.K. Huang, D.Sc., a professor of radiology and biomedical engineering at the University of Southern California, discussed a CAD-PACS software toolkit, developed at the school's Image Processing and Informatics Laboratory, that uses DICOM, HL7, and Integrating the Healthcare Enterprise profiles for integrating CAD results with PACS workflow.

The CAD software toolkit is modular and can be installed in a stand-alone CAD workstation, a CAD server, a PACS workstation, a PACS server, or a combination of the systems.

In general, CAD companies favor approaches that don't require them to get into PACS software, which is extremely complex, whereas PACS companies would prefer acquiring CAD and integrating it with their own PACS, Huang said.

His report discusses several versions but recommends two.

One version uses the DICOM screen capture service to store CAD results for viewing purposes only. It is simple to design and implement but is seldom used in clinical research.

A second version uses the DICOM structure report (SR) service and several IHE workflow profiles. Huang calls the methodology elegant but notes that it requires several modules of the toolkit to be installed in the PACS server, which would necessitate intensive collaboration with the PACS vendor. He says the integration would require patience and perseverance from the integrator because of the protective culture of PACS businesses.

A third version uses DICOM SR and the Key Image Note IHE Profile. The method reduces the need to alter the current PACS server and leaves CAD results in the CAD server, not in the PACS. This version is favored by CAD manufacturers because they are able to install the toolkit in their CAD server and integrate CAD results with the clinical workflow.

Huang recommends the last two versions, which he considers the "correct" methods of integrating CAD with PACS, because direct CAD results in clinical workflow would enhance future PACS research capabilities and improve the utility of medical imaging informatics infrastructure. (Int J Comput Assist Radiol Surg 2008;3[1-2]:27-39).

Close CAD-PACS integration does yield workflow gains, according to Dr. Peter Herzog, a chest radiology fellow at the University of Munich in Germany. He uses two Siemens CAD systems, for chest x-ray and lung imaging, that are integrated with three Siemens PACS, including a Sienet MagicView software package.

The integrated systems, which have been used at the university's large teaching hospital for about two years, allow all data to be transferred from one PACS to another, all of which are connected to a CAD manager.

The advantage of the integrated systems is that no interface is required between the systems, allowing data from CT chest images to be sent automatically to the CAD manager, which starts the necessary utility process. The CAD manager then determines where the data are coming from and sends the results to the correct PACS.

"It works in the background. It's just a box somewhere in the closet," Herzog said. "Nobody has to work with it."

When Herzog opens a lung study in PACS to see the original images, the integrated system displays a second image with CAD markers on it, showing every potential pulmonary nodule with a circle around it.

While Herzog considers his CAD systems to be very robust, he would like to see future systems do more than just detect nodules.

"Perhaps they can do measurements on nodules, especially based on CT data," he said. "We need diameters, we need volume."

The current integrated process still requires a dedicated workstation, which adds a step to the workflow. Herzog and his colleagues read all studies from PACS, then dictate a report into a speech recognition system.

"I would prefer if it could detect and evaluate data automatically without user interaction," Herzog said.

Toronto-based Medipattern recently announced an agreement allowing iPACS to integrate the company's B-CAD into its product line for reading breast ultrasound exams. The integrated system provides an interactive workstation in B-CAD, providing the ability to read the image, make changes, and create a report, said Janet Sterritt, Medipattern's vice president for business strategy and marketing. The B-CAD system can be adapted to integrate with other PACS as well.

The company's ultrasound CAD not only detects and locates lesions but also uses 42 different descriptors to help classify what has been found to determine if it is probably malignant or benign.

Carestream sells adaptable CAD systems for mammography and pulmonary applications. The company's pulmonary CAD is sold only in China, where annual screenings are required because of the high incidence of lung cancer, a result of widespread smoking among the population.

A structured report from the CAD server is transferred to a PACS workstation, which allows the user to see the image and the report together, said Ron Muscosky, worldwide product line manager for Healthcare Information Solutions, Carestream Health.

Carestream's CAD products are designed to be integrated with most PACS. The company's PACS mammography system allows a single log in, providing a tight integration that launches a third-party application on the same desktop, Muscosky said. It then transfers the user name and password and patient context so the third-party application will display the information of interest. This is all done automatically.

More and more clients, especially those using computed radiography and full-field digital mammography, want integrated CAD-PACS systems, Muscosky said.

Fujifilm markets Synapse PACS, which displays and archives images and patient information that are DICOM-compliant. Synapse is web-based, giving users the capability to go to any workstation on the network and, via sign-in, obtain information they have been authorized to access.

Fuji's Synapse can be adapted to display different CAD applications, such as those from iCAD or R2, whereas many PACS can display the marks of one company or the other but not both, said Andrew Vandergrift, national marketing manager for women's healthcare.

As the availability of digital mammography increases, so will the demand for integrated systems, Vandergrift said.

"We foresee the integration of PACS and CAD becoming a requirement over the next couple of years," he said.

Cristine Kao, senior marketing manager at GE Healthcare, which markets a PACS among its offerings, said the trend is that customers want to do everything from a single desktop.

"They want to be able to read multimodalities, not just CAD from breast imaging," Kao said. "They want clinical information for a patient in CT or ultrasound. They want to be able to report and sign off on an exam in one single workflow. Every healthcare center or customer that has breast imaging has asked for this."