Molecular Imaging's Next Generation: How Molecular Contrast is Changing Radiology
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| Siemens Biograph mCT |
“Siemens Biograph mCT will more explicitly merge the molecular imaging capabilities of PET with the morphological diagnostic capabilities of CT due to the high performance of each component,” explains Paul Shreve, MD, medical director, PET Medical Imaging Center and medical director, adult radiology at Spectrum Health in Grand Rapids, Mich. The center is slated to become one of the first U.S. adopters of the Biograph mCT.
On the clinical side, molecular CT technology offers a very neat package for a wide range of applications including cardiac PET/CT, perfusion imaging, virtual colonoscopy and radiation therapy planning, says David Townsend, PhD, director molecular imaging and translational research program at University of Tennessee Graduate School of Medicine in Knoxville. It’s also very quick. The throughput potential of mCT is promising as the new system completes routine, whole-body PET scanning in five minutes.
This issue, Molecular Imaging Insight visits several clinical leaders to explore the vision for molecular imaging’s next generation.
Clinical possibilities
The marriage of HD•PET and advanced CT makes for a clinical powerhouse that is expected to expand and improve PET/CT applications. A growing body of research indicates that reconstruction techniques like HD•PET and HD•PET plus time-of-flight technology offer the potential to improve physicians’ abilities to diagnose and treat cancer. “With the new ultraHD•PET technology, images are sharper and better, allowing much more precise depiction of the disease and increasing sensitivity,” explains Tiago Mundim, MD, radiologist at Clinica Villas Boas in Brazil. The best of both worlds, hybrid imaging offers a range of improvements in existing protocols.
The University Hospital of Essen in Germany, for example, currently taps into PET/CT for colon cancer patients. The hospital’s radiology staff looks forward to evaluating the potential of Siemens mCT in its colon cancer imaging program. The new system could improve diagnostic accuracy. “Fast CT and high-definition PET imaging could produce high-resolution slices that offer more accurate interpretation of tumor infiltration into the colon wall,” poses Gerald Antoch, MD, a radiologist.
Another intriguing possibility arises from the scanner’s perfusion imaging capabilities. Current protocols utilize CT functionality to measure tumor perfusion. Radiologists could measure therapeutic response with molecular CT, gaining critical information about tumor perfusion and FDG uptake to assess whether or not perfusion decreases during the therapeutic course. The data could be used to enhance clinical decision-making, providing physicians with more comprehensive data about a tumor’s response to a given therapeutic modality. The combination of advanced PET technology and whole organ perfusion capabilities could prove particularly helpful by enhancing characterization of lung, liver, brain and retroperitoneal lesions in a single scan.
Over the past two years, more sites have integrated PET/CT into radiation therapy treatment planning; however, the application remains in its formative stage. Although current PET/CT systems handle radiation therapy treatment planning, they leave room for improvement. “Molecular CT will more explicitly meet the needs of radiation therapy treatment planning,” says Shreve. That’s because the system combines state-of-the-art PET and CT technologies in one platform for the first time to provide the radiation therapy team ultra-precise information about the anatomy and physiology of the tumor. In addition, the system incorporates a large 78 cm bore to better accommodate radiation therapy planning and positioning devices.
Molecular CT also better enables cardiac PET/CT, solving some challenges that confound cardiac imagers. For example, the scans of patients with higher heart rates tend to be obscured with artifacts. “The inclusion of a CT scanner capable of up to 128 slices offers an opportunity to scan patients with higher heart rates,” shares Antoch. What’s more, HD•PET may allow physicians to visualize inflammatory changes in the coronary arteries.
Wedding workflow and economics
Molecular CT could reinvent PET/CT economics. But PET and CT in one room is not a new idea. The difference is that unlike first-generation hybrid PET/CT that was used for anatomical mapping, molecular CT components are state-of-the-art, and PET exams have evolved from taking 20 minutes, to a routine 5 minute PET/CT exam. In addition, the widespread availability and prompt delivery of FDG have made traditional nuclear medicine technologies standard diagnostic tools. Nuclear medicine and radiology are collaborating and working more closely together with the advent of hybrid imaging. With the advanced PET and CT technologies in molecular CT, the clinical value of the studies are enhanced, and it makes sense to employ the system in a shared service capacity.
The new economics of imaging require sites to maximize scanner utilization. Sites employing molecular CT technology can emphasize the independent use of the scanner’s CT capabilities during the work day to increase the number of daily scans, says Shreve, who envisions some centers easily completing 20 to 30 PET/CT and independent CT scans daily on the new system. Antoch predicts University Hospital will increase its daily PET/CT patient volume from 15 to 25 patients.
At the same time, molecular CT facilitates the cost-effective, one-stop shop approach to integrated PET/CT imaging. The superior capabilities of both components allow advanced CT techniques like organ perfusion and CT enterography to be incorporated into a combined PET/CT study in a single patient visit, which conserves human resources, increases patient convenience and accelerates decision-making and the clinical care cycle.
The patient factor
Diagnostic radiology can not overlook patient safety, comfort and convenience. Molecular CT will deliver. The ultra-short scan time, for example, would allow physicians to complete PET/CT virtual colonoscopy studies in five minutes compared to 30 minutes on standard PET/CT systems, a major plus for patients with insufflated colons. “The patient comfort factor could make virtual colonoscopy more acceptable,” opines Townsend. The system also maximizes opportunities for minimum radiation dose; it incorporates Adaptive Dose Shield technology to limit radiation dose, and advanced PET technology allows reduced dose or shortened scan times.
Interesting, too, is the spike in virtual colonoscopy use in recent months following a multi-site American College of Radiology Imaging Network (ACRIN) study published in the New England Journal of Medicine that proved its effectiveness, deeming it equal in performance to traditional colonoscopy. It also was endorsed in new screening guidelines from the American Cancer Society. Among the pluses: virtual CT scan is less expensive, requires no sedation, does not require a day out of work, is generally more accepted by patients and could gain CMS coverage soon (the agency is expected to complete its coverage review in February). Five-minute scan time could be all the more enticing to patients and could even potentially increase screening rates that remain low, largely because traditional colonoscopy is perceived as unpleasant and invasive.
Looking ahead
As pioneers prep to deploy Siemens Biograph mCT, many anticipate the next stage of molecular imaging. “Looking ahead to the next two to three years, molecular imaging will become the standard procedure to evaluate patients with cancer, cardiac or neurologic diseases. New tracers will become available, improving patient care. We will be able to detect illness before it becomes clinically apparent, and we will probably predict illness, too,” predicts Mundim.
Delivering on molecular imaging
Molecular CT delivers on the promise of molecular imaging by pairing advanced PET capabilities with state-of-the-art CT in a single package. The high performance package provides radiologists a platform for improved visualization and delineation of lesions, accelerated, more comfortable PET/CT radiation therapy planning and enhanced cardiac PET/CT. In other words, Biograph mCT bridges the gap between the promise and practice of molecular imaging.