PET: Making the Numbers Work

Twitter icon
Facebook icon
LinkedIn icon
e-mail icon
Google icon
balance_1338308445.jpg - Balance

Cardiac PET has always taken a backseat to SPECT imaging in terms of volume. But, whether it is the quality of PET images or recent technetium-99m isotope shortages, more providers are giving PET a second look. Before committing, they need to consider the financial and practical challenges of introducing a cardiac PET program.  

The top concern is patient volume, says Kim Allan Williams, MD, cardiology chair at Wayne State University School of Medicine in Detroit. Many practices are not large enough to take on the substantial fixed costs of a rubidium tracer generator or a cyclotron and make it financially feasible. An outpatient facility would need to see at least three cardiac PET patients per day five days a week to break even, and that number changes dramatically as reimbursement changes, according to Williams.

"That sounds like a small enough number, but you have a lot of competing technologies," he says. "There's stress MRI, stress echo, SPECT perfusion imaging—all of which are validated methods of giving similar information as PET. The number of patients who require viability assessment—an area where PET excels relative to the other techniques—is a smaller percentage of the patients being imaged."

PET provides better image quality than SPECT in any given population; however, the best candidates for PET are patients who are likely to have significant attenuation artifacts, such as obese patients or women with large or dense breast tissue that significantly limits SPECT, says Paco E. Bravo, MD, of Johns Hopkins Medical Institutions in Baltimore.

Aside from these specific populations, most patients who undergo studies to rule out coronary artery disease will have a diagnostic test other than PET. But Bravo says there has been an increase in PET utilization for other indications, including risk-stratification of patients using absolute myocardial blood flow quantification, as well as diagnosis and evaluation of forms of cardiomyopathy.

Currently, the dominant use of PET imaging is in oncology exams. Tumor imaging represents approximately 90 to 95 percent of total PET volume, according to the Advisory Board. While this means cardiac PET studies will be competing for space within oncology departments at facilities that aren't dedicated cardiac centers, Williams says this should be seen as an advantage because of the ubiquity of PET scanners. "The success in oncology means some scanner time could be devoted to cardiology studies," he says, though splitting that time with oncology doesn't help with cardiac PET tracer fees.

Figuring the logistics

Tracer fees are some of the main logistical differences between cardiac PET and SPECT. While SPECT tracers have a relatively long half-life and can be ordered on a per-dose basis, PET is a fixed-cost model, explains Howard C. Lewin, MD, of Cardiac Imaging Associates in Los Angeles. Providers need to know they have enough patients to afford the rubidium generator, which can cost as much as $450,000 per year when including shipping and all equipment.

While the costs of PET tracers are high, radioisotopes used in SPECT have their own headaches, specifically the instability of the technetium-99m supply. Over the past few years, the supply of molybdenum-99, the parent isotope of the technetium tracer, has been in turmoil due to aging, less reliable nuclear reactors, leading some molecular imagers to look for alternatives.

Another logistical consideration is the physical structure of the facility where a PET scanner is to be installed. PET/CT hybrid scanners are larger and heavier than SPECT cameras, says Lewin, and may need structural support before installation. Higher energy PET tracers may require more shielding in the imaging room as well. PET/CT systems typically require a room measuring 14 feet by 24 feet, and must accommodate the rubidium generator, an infusion pump and the technologist along with the actual camera and control area (J Nucl Cardiol 2011;19:12-18).

Show me the money

Reimbursement for cardiac PET has been rocky. The Centers for Medicare & Medicaid Services (CMS) cut reimbursement for cardiac PET by 23 percent in 2011, following cuts to SPECT the year before. When reimbursement drops, volumes have to increase to avoid losses, but all efforts are being directed toward strict appropriate imaging for patients, says Williams.

In the absence of a national coverage policy, local coverage determination allows local carriers not only to determine the approved indications