Multimodality Cardiac Diagnosis: Cardiac Fusion Imaging Comes to the Desktop

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GE LightSpeed VCT and workstationSponsored by an educational grant from GE Healthcare

Sixty-four slice CT scanners, like GE Healthcare’s LightSpeed VCT, have re-invented cardiac imaging. At the same time, anatomical imaging alone does not provide physicians all of the data needed to make an accurate diagnosis. Many cases require an analysis of physiologic data such as perfusion or viability data generated by PET or SPECT scans as well as review of the 64-slice CT dataset. Conventional means of reviewing images generated by separate imaging modalities are far from ideal. A remedy for the situation, however, has moved from the drawing board into clinical practice.

Last year, GE Healthcare introduced VolumeShare2, a new advanced visualization and analysis toolkit for its Advantage Workstation (AW). This platform incorporates CardIQ Fusion, a new application that allows physicians to fuse CT and PET or SPECT imaging data on the AW workstation. The application was awarded the Society of Nuclear Medicine (SNM) annual 2006 Image of the Year.

Philipp Kaufmann, MD, director of nuclear cardiology at University Hospital Zurich in Switzerland, explains the clinical significance of CardIQ Fusion. “It can be difficult to determine if a cardiac lesion is likely to produce ischemia with anatomic data alone. The problem is exacerbated in patients with multiple lesions. The physician interpreting the CT angiogram may not be able to associate each lesion with its territory and ischemia. Intermediate grade lesions present another diagnostic challenge as the severity of the patient’s disease can be unclear based on anatomical data.”

Accurate diagnosis for such cases hinges on analyzing perfusion data and anatomical images. Until recently, physicians were hampered by archaic manual processes. Functional images generated by nuclear medicine scans and anatomical data garnered during the CT angiogram resided on separate workstations or applications. Physicians needed to switch back and forth between applications to review both types of data; then, they might mentally overlay typical coronary vessel anatomy on the physiologic data or theoretically fuse physiologic and anatomic datasets. In both cases, the process presented clinical and workflow challenges.

“GE has solved this challenge of fusing anatomical and functional data,” says Kaufmann. The company’s VolumeShare2 advanced image visualization and analysis tool with CardIQFusion transforms the AW into a cross-modality viewing platform. It provides a one-stop shop process for fusing CT, PET and nuclear medicine imaging datasets.

CardIQ Fusion fuses perfusion images produced from nuclear medicine or PET studies with the anatomical data generated during a CT study on the AW. The application provides clinicians with the tools to review and analyze angiographic data from CT for standard anatomic assessments such as vessel analysis, stenosis detection and quantification. The plus with CardIQ Fusion is that the software also allows physicians to assess physiological data such as perfusion and viability from PET or SPECT studies on the same workstation. Kaufmann and his colleagues helped refine the application and have used it in conjunction with the LightSpeed VCT scanner and AW on a daily basis for nearly two years.

“The fusion of perfusion and anatomical images helps us determine whether or not a specific lesion is associated with a perfusion defect and ischemia,” explains Kaufmann. The clinical impact is significant. “Associating the lesion with its territory allows us to make a more appropriate diagnosis, which results in a better treatment,” Kaufmann notes. In the end, CardIQ Fusion could help physicians meet the ultimate goal of improved prognosis for patients with cardiac ischemia.


CardIQ Fusion: The clinical process

University Hospital relies on a team approach to cardiac imaging. The team consists of nuclear cardiologists and CT radiologists. The group uses the LightSpeed VCT and the Discovery PET/CT in conjunction with AW and CardIQ Fusion on an array of patients including those with coronary artery disease, ischemia and arrhythmia. CardIQ Fusion can be deployed if a previous PET or SPECT study exists. CardIQ Fusion also may be used if the patient undergoes a hybrid PET/CT or SPECT/CT scan.

Two groups of physicians refer patients for CT angiography. Cardiologists form the first group. “They appreciate CardIQ Fusion because its enables a comprehensive assessment of the patient. The cardiologists send the patients to our department for a CT angiogram. After we perform the study and complete the reconstructions and fusion we send the patient [and results] back to the cardiologist. He has the images and information he needs to decide on an appropriate treatment,” sums Kaufmann.

Cardiac surgeons comprise the second group of referring physicians. Cardiac surgery candidates require a diagnostic procedure, like CT angiography, prior to surgery. The surgeons refer patients to the cardiac imaging department; the combination of a 64-slice LightSpeed VCT, PET or SPECT scans and CardIQ Fusion produces the anatomical and functional information necessary for the patient to proceed to surgery. “The CardIQ Fusion-enabled reconstruction yields images and information required for bypass surgery,” says Kaufmann.


Cardiac fusion: Overcoming challenges

CardIQ Fusion overcomes the primary challenge related to multi-modality cardiac image viewing. That means that the application registers both anatomical and physiological information semi-automatically. Physicians use AW to view 3D and 2D data for optimal assessment of the patient’s cardiac status. The fused dataset enables clinicians to correlate anatomic and physiologic information and determine the appropriate treatment protocol.

A secondary challenge, says Kaufmann, is demonstrating that CardIQ Fusion produces a true image. Over the last two years, Kaufmann and his colleagues have proven that the technology does render a true fusion image set and will publish the results later in 2007 in the European Journal of Nuclear Medicine.

Other challenges relate to the clinical use of the software. Until CardIQ Fusion, the marriage between physiologic and anatomic data was imprecise and fuzzy. “We needed to find a way to convince referring physicians of the value and viability of this approach,” recalls Kaufmann. Referring clinicians desire a clear diagnostic roadmap. Images yielded by CardIQ Fusion sell themselves, says Kaufmann, and persuade physicians of the clinical utility of fusion imaging.

As with any technology, there is a learning curve. “VolumeShare2 with CardIQ Fusion helps accelerate the learning curve for physicians. It meets their need for reliable, robust software with a user-friendly interface,” explains Kaufmann. Training is still required, he says, but the application’s interface moves users along the learning curve.  


Conclusion

Cardiac imaging is evolving. Sixty-four slice volumetric scanning has opened the door to non-invasive imaging of the coronary arteries. At the same time, 64-slice images do not provide a complete picture of the patient’s cardiac status. Physiologic data are equally important.

The challenge has been finding an efficient means to review and fuse anatomic and physiologic datasets to create a more accurate image of the cardiac anatomy and function. GE’s VolumeShare2 with CardIQ Fusion offers a solution. It allows users to wed CT anatomical data with physiologic data such as perfusion or viability data generated by PET or SPECT studies. With CardIQ Fusion, the utility of AW grows. Physicians can use the workstation to review CT angiography data for stenosis detection, vessel analysis and quantification. In addition, the CardIQ Fusion software provides a means of evaluating physiologic data such as perfusion and viability on the same AW platform. Finally, anatomic and physiologic datasets can be registered and fused, enabling physicians to correlate both types of data to link specific lesions with ischemia and devise an appropriate treatment regimen for the patient. “CardIQ Fusion improves patient care by allowing us to better target treatment and interventions.

The software also helps our department enhance service to referring cardiologists and cardiac surgeons,” sums Kaufmann.