Technology Update: PET — Equipment Manufacturers Pursue More Quantitative Data From Exams
By Keith Loria
Vol. 15 No. 5 P. 24
While oncology exams dominate the modality, cardiology and neurology exams are growing, too.
Developing truly quantitative PET exams that consistently measure tracer uptake in a voxel is a key step in improving PET’s value in improving cancer diagnosis and assessing whether treatment is working. Accurate quantitation needs a consistent measurement. Clinicians not only want the ability to detect smaller lesions, but the ability to assess whether patients are responding to treatment. Manufacturers are working to expand their PET/CT capabilities in this area to meet that demand.
“GE Healthcare has invested in technologies and tools to help clinicians achieve a better level of quantitation and consistency from study to study,” says Wei Shen, general manager of PET/CT. “Reducing parameters in the scanner that impact PET measurement inaccuracy has been GE’s priority.”
Like other manufacturers, GE is pursuing PET/CT advancements in its Optima and Discovery systems to improve resolution in scanners and lower patient dose. “Our approach of lowering dose, both from the diagnostic CT with ASiR [adaptive statistical iterative reconstruction] and from injected dose, is a key pillar of our advancement of PET/CT technology,” Shen says. “Also, our motion correction and motion management technologies correct for blurred artifacts in areas subject to respiratory motion of the body, such as the lung and liver. This helps in the diagnosis and staging of a lesion that may be masked by motion artifacts.”
At RSNA 2013, GE Healthcare showcased Q.Clear, which provides a more quantified standard uptake value (SUV) in a PET scan. Q.Clear received its 510(k) approval in April.
“Clinicians will soon have a tool to more quickly and confidently evaluate their patient’s response to their cancer treatment utilizing Q.Clear, which provides up to two times improvement in both PET quantitative accuracy and image quality,” Shen says.
Philips Healthcare unveiled its new digital PET platform, Vereos PET/CT, at RSNA 2013. “Vereos offers advances in PET performance due to our proprietary digital photon counting [DPC] technology,” says Kirill Shalyaev, Philips’ senior director of product marketing for advanced molecular imaging. “DPC provides approximately two times improved sensitivity gains, two times better volumetric resolution, and two times better quantitative accuracy compared to conventional time-of-flight PET performance.”
These advances offer the opportunity to manage dose, reduce scan times, and enhance lesion detectability. The DPC technology has allowed Philips to redesign its system architecture to create the shortest bore among PET/CT scanners, according to the company.
At SNMMI 2013, Siemens introduced its Biograph mCT Flow PET/CT system. With earlier PET/CT scanners, planning and scanning is limited to the fixed size of the system’s detector field of view for each bed position. With its new anatomy-based FlowMotion technology, Biograph mCT Flow is the first PET/CT system to offer continuous motion PET/CT scanning, according to the company. The technology eliminates dose related to overscanning, and a 78-cm bore may help reduce patient claustrophobia.
“All of the vendors up to this point have used a stop-and-go–type bed motion, much like the old CT scanners and MRs used to do, but now we have continuous bed movement throughout the entire scan,” says Robert Brait, Siemens’ national PET/CT product manager. “The advantage to that is you can now incorporate multiple workflows into one scan.”
For example, within a single scan, there can be a high-resolution image of the head and neck and motion management in the chest along with using some very high-level reconstructive algorithms that can require images from the abdomen and lower pelvis—all done without stopping.
“Our customers were asking for a way to incorporate everything into a single scan, looking to drive clinical outcomes more accurately and be more effective operationally,” Brait says. “We are manufacturing our systems to make sure they have upgradable abilities, so if they buy any one of our scanners, they can upgrade the performance either on the PET side or CT side as they do more types of imaging.”
John Aarsvold, PhD, an imaging scientist, applied mathematician, and clinical nuclear medicine physicist and president of SNMMI’s computer and instrumentation council, says F-18 FDG PET/CT imaging of appropriate cancer patients is, at present, the most prevalent use of PET/CT technology. “For appropriate patients, therapy-monitoring studies performed every several months provide oncologists information that can be used to assist in decision making,” he says. “For other patients with cancers for which F-18 FDG PET/CT is appropriate, such studies provide their surgeons with preoperative information that can better ensure surgical successes and, at times, result in shorter surgeries.”
Aarsvold adds that rubidium-82 chloride PET/CT and nitrogen-13 ammonia PET/CT are being used clinically in studies to assess myocardial perfusion; F-18 florbetapir PET/CT and F-18 flutemetamol PET/CT are used clinically in studies to detect and quantify beta-amyloid levels in brains; and C-11 choline PET/CT is used clinically to help detect recurrent prostate cancer.
Clinical PET/CT exams and research require different forms of expertise. According to Aarsvold, there are several areas of research activity further testing what the technology can do, including the following:
• quantitative brain PET and brain PET analysis, which may encompass dedicated brain PET/CT technologies, kinetic modeling, analysis algorithms, and analysis software;
• PET/CT for prostate cancer, which likely will involve novel radiopharmaceuticals and perhaps dedicated prostate PET/CT technologies;
• Gallium-68 DOTA peptides PET/CT and therapies of yttrium-90 and lutetium-177 DOTA peptides; and
• new F-18 labeled radiopharmaceuticals for cardiac myocardial perfusion imaging.
Aarsvold notes that further evolution of clinical PET/CT requires not only the development of radiopharmaceuticals and technologies but also involves the means to produce, deliver, and obtain reimbursement for both the radiopharmaceuticals and data acquisition, analysis, and interpretation.
SNMMI works to coordinate efforts in these economic areas, Aarsvold notes, so the technologies can evolve from research to day-to-day clinical tools that benefit patients.
One of the biggest challenges that health care organizations face is the ongoing pressure to provide accurate and meaningful diagnosis with the equipment available today at the lowest cost possible to maintain profitability in the current environment of reduced reimbursement. According to Shalyaev, reimbursement formulas will move toward rewarding the quality of outcomes and away from traditional volume rewards. For this reason, customers will demand greater accuracy and confidence from the information provided by the imaging equipment.
“DPC provides the greatest SUV accuracy of any PET scanner and will have the potential to help customers tackle the challenges faced in their environment today,” Shalyaev says.
Conventional PET/CT systems often require clinicians to choose between protecting patients through lower dose and enhancing productivity through faster scans. “GE’s PET/CT solutions are engineered to deliver high image quality, diagnostic confidence, and robust reports that our customers, their customers, and referring physicians can use to help get the best answers for their patients,” Shen says. “We are working hard at developing the next generation of technology, making it more affordable and accessible to every corner of the world so more clinicians can use this technology to help save lives.”
The equipment manufacturers interviewed for this article believe PET/CT will continue to be a growing part of radiology and imaging departments. “With advances in imaging technology, the expansion of clinical procedures will continue to grow and offer more accurate information for diagnosis in studies, not only in the conventional oncology staging procedures, but also in areas such as cardiology and neurodegenerative diseases,” Shalyaev says. “With new detector performance, we are going to see a step in improvement in the way PET/CT is used in practice today and further expand the clinical range of diagnostic imaging.”
The vast majority of PET/CT imaging done today is in oncology, with about 95% of all exams, followed by about 3% in cardiology and 2% in neurology, according to Brait. “We see in the future that oncology will become more robust with more of a demand, and our customers can easily take their CT scanner out of their PET/CT system and take it from a 20 slice all the way up to a 128 slice,” Brait says. “An upgrade takes about 2 1/2 days.”
Looking five years down the line, Brait believes that hybrid imaging will be used far more than it is now. “It just makes sense. There’s a true value because you are combining multiple imaging modalities,” he says. “I think there’s going to be a continual drive to get improved, quantitative results. Once you can apply a number to it, you now have magnitude and direction and that drives to clinical outcomes.”
Aarsvold says SNMMI’s work is important for the future of the PET/CT industry for several reasons, particularly in providing accurate quantitation of radiopharmaceutical uptake and ensuring the development of technologies and techniques that result in accurate quantitative PET data and images. “As knowing physiological and anatomical changes over time is often useful, some patients receive several FDG PET/CT studies over months, even years,” he says. “Accurate determination of the uptakes in each study provides a means of comparing a patient’s recession or progression of abnormality. In such analysis, accuracy matters.”
It will be important to have access to more PET/CT with scalable platforms that customers can upgrade in the future as their needs change. Therefore, Shen believes the future will bring greater PET/CT access to more patients and more new organ- and disease-specific PET tracers.
“As PET/CT becomes more ubiquitous and used by more physicians around the world, our goal is to help meet the need of customers with GE Healthcare technologies,” he says. “Better quantitation that standardizes the PET measurement—giving physicians more confidence—is an important piece of the future. This will lead to more multicenter clinical trials that will show the power of PET/CT as a standard of care for diagnosis through treatment assessment in patient care.”
— Keith Loria is a freelance writer based in northern Virginia.