PET/CT: Charting the Treatment Course

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This image, captured on Siemens Biograph, illustrates a malignant nodule in the right lung.Technological advances combined with increasing awareness of the benefits of PET/CT among the general physician population has the modality poised for growth. Proponents are gathering the data needed to widely prove the modality’s ability to provide important measures of cancer treatment. The newest generation addresses the growing rate of obesity and indications increase regularly.

“I’ve been a diagnostic radiologist for 32 years and this is the most exciting time in my life to practice PET/CT, says Joe Busch, MD, radiologist at Diagnostic PET/CT Center of Chattanooga in Tennessee. “Practicing oncology with PET/CT is the most exciting thing I’ve ever done in radiology. It changes patients’ lives, changes therapies, and changes what you do to a patient.” Busch notes that 30 percent of the time, the information gathered via PET/CT changes a patient’s course of treatment.

More and more see the benefits

Busch and his colleagues use Siemens Medical Solutions Biograph 6 and Biograph 16 PET/CT scanners. The equipment lets them simultaneously perform diagnostic CT and PET imaging. The PET/CT scanner allows for image correction. “This is true hybrid imaging,” he says. With a 16-slice scanner, he figured “why not use it like a real CT scanner? We do biopsies, therapeutic injections and more.” The primary use is to stage and restage cancer, and measure therapeutic response — measuring both physiology and looking at morphology.

Kevin Berger, MD, director of PET imaging in the department of radiology at Michigan State University in Ann Arbor, agrees that using PET/CT to scan cancer patients often results in important changes to treatment, such as detecting a metastasis that wouldn’t have been found otherwise. His department uses the Discovery PET/CT system from GE Healthcare. “It lets us better define where a patient has disease. That’s why PET has grown — it has been so useful and so critical to making changes and decision-making that affects patients.”

Anthony Larhs, MD, director of nuclear medicine and clinical PET at TRA Medical Imaging in Tacoma, Wash., has been using the Gemini TF PET/CT from Philips Medical Systems since December 2006. Just four or five years ago, only medical or radiation oncologists could talk about this modality, he says. As clinical research has evolved and more meetings have included presentations on PET/CT, more physicians are aware of the benefits of this technology. Many more surgeons and internal medicine physicians are starting to use PET/CT, he says. “It takes a certain amount of time to disseminate the knowledge to the community. That change has partially occurred.”

Gemini TF features TruFlight technology, which identifies the time difference in detection of the two coincident gamma rays to within a billionth of a second (roughly the speed of light) which facilitates calculation for the reconstructed image. TRA is the first facility to install the system west of Denver and only the 28th organization worldwide.

Larhs says that many so-called technological changes are really marketing hype or small changes that don’t justify the purchase of new equipment. TruFlight technology, however, is “quite a tremendous feat. It improves sensitivity by nine times. That’s amazing.” And, contrary to other modalities, TruFlight allows PET/CT imaging to improve as a patient’s size increases. “All imaging modalities deteriorate and cannot perform well if the patient is heavier. We cannot offer the same quality of medicine because we can’t see very well deep inside the body.” Because time-of-flight increases along with the waistline, “we start to see equivalency of medicine” for obese patients. Larhs says that it becomes a social and medical responsibility for clinicians to refer their heavy patients to PET equipment that has time-of-flight capability.

Diagnos PET/CT Imaging is a new facility in Houston, Texas, devoted to PET/CT. Although the vast majority of procedures are for neurological or oncological conditions, the facility has a mix of physicians, including internists, general practitioners and a gastroenterologist. When the facility opened about a year ago, the goal was a tranquil environment in which patients could get the best possible care, says Graham Williams, COO. The group of 20 physicians uses the Sceptre P3 PET/CT system from Hitachi Medical Systems America. “Starting from scratch, it’s apparent you have to educate. PET/CT is little understood by the physician community,” he says, but the market is growing because the modality is no longer limited to oncology and neurology.

Reimbursement cuts a hindrance

Even as efforts are being made to disseminate information about the benefits of PET/CT imaging, the Deficit Reduction Act (DRA) is having a negative impact on reimbursement for the modality, as it is in many other areas. While many centers can manage the cuts by increasing their patient throughput, Berger notes that that isn’t an option for everyone. “It’s a matter of where you practice. At institutions that are relatively rural, it might be very hard to increase volume.” His own facility has seen an increase in procedures of about 10 percent over last year.  

Reimbursement cuts are hindering the development of PET imaging, says Larhs. “For the past few years, the move has been to support PET in imaging. This is the first time we are getting a blow [in reimbursement] and it is quite a significant blow.”

The payment changes are following the same pattern of reimbursement that hit MRI and CT imaging, says Williams. On the other hand, Medicare has established the National Oncological PET Registry. Subscribers can register each procedure and a request for payment. If the organization approves it, Medicare will pay for it. The registry “has been very helpful to the PET/CT community,” Williams says. The process allows for exploration of all usages of PET/CT and opened the door to greater diagnosis of cancer, he says.

Until the registry and other sources of data can prove the value of PET/CT, the DRA “is going to hit radiology hard,” says Busch. Fewer organizations will invest in PET/CT, he says, at least until they can see if they can make ends meet. The problem is that many practices developed a five-year business plan and now the reimbursement cuts are forcing changes to that plan midstream. Meanwhile, they won’t hire as many people as they might have and work their current staff harder. “We don’t want to overstaff, but we don’t want to burn them out either.”

On the horizon

Beyond cancer and neurology imaging, PET/CT is making inroads in areas such as cardiology. Berger has been working with GE Healthcare on myocardial perfusion reserve — looking at blood flow and doing absolute quantification. Normally, clinicians look at relative perfusion but “if the perfusion of the heart is globally impaired because of symmetric stenosis, if everything is diseased, it’s hard to tell,” he says. “You can quantitate the perfusion of the heart and look at these absolute differences and see if patients have severe disease.” This can more accurately help determine which patients should undergo cardiac catheterization, who might have been overlooked.

Most of the newest PET/CT features are software driven, says Williams, including more enhanced images and features for specific organs. For example, he has been using a brain study program from Hitachi that allows for comparison of a patient’s scan with 30 to 40 “normal” brain scans. “You can see differences according to gender and age,” he says. “The doctor can get a much better profile and more easily pick up anomalies.”

Also on the horizon for PET/CT imaging are new radioisotopes that will make a big impact, Berger predicts. Tracers in development have shown promise in quantitatively assessing disease burden, particularly for dementia. However, “some of the real promise really depends on the translation of these radiopharmaceutical applications to the clinics.”

In general, this technology has reinvented itself every five years, says Larhs. But given the recent developments, “chances are that there will not be another break in the technology so soon. Chances are that we have reached maximum resolution.” Next is how to best measure changes, improving the ability to look at metabolic activity and the capability to better describe changes.

“We already know [PET/CT imaging’s] value in staging and restaging cancer,” says Busch. “We are learning more all the time about monitoring therapeutic response.” Oncologists want data to more accurately monitor cancer therapy, however, and “it’s going to take some time to get the data.”