A great evolution of the payment structure for imaging procedures is occurring. Soon, payers will reward cost-effective, high-quality procedures, while both healthcare providers and patients increasingly will demand efficient, diagnostically accurate nuclear cardiology procedures with low radiation exposure.  Because of the favorable qualities of cardiovascular positron emission tomography (PET), this modality is poised to thrive in this new environment.

Challenges ahead for SPECT

Single photon emission computerized tomographic (SPECT) imaging has been successful in identifying coronary artery disease (CAD) and assessing patients’ risk for future cardiac events; however, challenges exist in all advanced cardiac imaging, including SPECT. For SPECT, the diagnostic accuracy has not changed in over 20 years, including the introduction of technetium-based tracers.  The accuracy is modest, leading to unnecessary downstream testing of patients with no disease. Camera technology has improved but has not affected either accuracy, outcomes or indications. Moreover, radiation exposure is higher than professional societies recommend and these levels are not being heeded. And recently, a major supplier of technetium to the US has closed, speculating a concern for supply and ultimately cost of the isotopes.  In a changing world, these issues with SPECT will become magnified.  Now, cardiovascular PET is emerging as a distinctive alternative to SPECT, in part because PET can image disease states that SPECT cannot

PET’s advantages

Cardiovascular PET uses tracers that are either cyclotron produced (18FDG, 13N-ammonia) or, in the case of 82rubidium, supplied by a Rb-82 generator, where the tracer is available to healthcare providers when needed. These sources are independent of technetium supply and are in abundance.  Cardiovascular PET perfusion imaging with either 13N-ammonia or rubidium-82 has consistently been shown to have significantly higher diagnostic accuracy than other current procedures, including SPECT and other noninvasive tests. With the greater accuracy comes higher image quality and lower radiation exposure to patients and staff. The higher diagnostic accuracy also translates into better physician and healthcare provider confidence and lowers unnecessary downstream testing. The reliability of high image quality gives interpreting physicians more assurance to deem studies positive or negative without equivocal terminology, thereby increasing referring providers’ confidence. A new advancement of assessing myocardial blood flow further enhances diagnostic accuracy. With cardiovascular PET perfusion imaging, radiation exposure is consistently low, in the range of 2-5 mSV, which is one-fourth to one-third less than with current SPECT procedures.

The ability to assess myocardial blood flow is a unique advantage of cardiovascular PET perfusion imaging that increases the accuracy of the test and makes it possible to identify other disease states, such as small-vessel disease, which is relatively common in diabetic patients. Of great clinical importance, the finding of normal PET perfusion and blood flow virtually eliminates the diagnosis of CAD as well as ancillary testing.

Data also suggest that metabolic imaging with FDG-PET is the best means for assessing myocardial viability in patients with heart failure and candidates for bypass surgery.

Inflammation imaging with FDG PET, especially for active cardiac sarcoid involvement, has become an important part of assessing patients with unexplained heart failure and lethal arrhythmias. FDG PET imaging also provides an important role in assessing therapies in patients diagnosed with cardiac sarcoid. With the same agent, FDG, infection imaging offers a unique means of noninvasively identifying infection in areas of device placement, such as pacemakers and implantable Cardioverter-defibrillators and even left ventricular assist devices.

These and other attributes led the American Society of Nuclear Cardiology and the Society of Nuclear Medicine and Molecular Imaging to sponsor a Position Statement that states cardiovascular PET myocardial perfusion imaging is “preferred” in all patients who are referred for pharmacologic stress imaging and is “recommended” in certain subsets of patients who, regardless of exercise status, have a challenging body habitus, high risk for CAD and cardiac events or great concerns about radiation exposure (J Nucl Cardiol 2016;23:1667).

PET’s economic sensibility

Cardiovascular PET makes clinical sense, but does it make good economic sense? The answer is a resounding yes. First, if the right instrumentation is chosen for the PET camera, all of the previously mentioned indications can be performed with the same camera. Thus, PET myocardial perfusion can be assessed using the same equipment for FDG viability, infection and inflammation imaging. Because of this, the camera is more likely to be in full operation on a daily basis. Second, perfusion imaging protocols are shorter for PET than SPECT, allowing more PET studies to be performed daily on a single camera yielding improved lab efficiency. Third, downstream testing can be aimed at treatment, not at confirming diagnoses, which will be an important attribute as payment models move toward rewarding value. Finally, the availability of the radiopharmaceuticals used in PET imaging is steady and able to meet growing demand.

Health systems and practices would be wise to consider these new developments as they invest in cameras, technologies and tracers. Cardiovascular PET is moving into the mainstream of nuclear cardiac imaging and is likely to thrive in the years to come.