The investigational PET contrast agent for myocardial perfusion imaging (MPI), flurpiridaz F 18, was found to be superior to MPI with SPECT for assessing coronary artery disease (CAD) in obese patients. The findings were presented yesterday by Lantheus at the American College of Cardiology’s annual scientific session in Chicago.

“SPECT image quality and accuracy decreases as BMI increases, due to a number of factors including more scatter, more attenuation, and lower counts,” Dr. Timothy Bateman, cardiologist at Mid America Heart Institute and the presenter of the study, told HCB News. “PET instrumentation reduces scatter and corrects for attenuation. PET quality is preserved as BMI increases, especially with F-18 tracers.”

MPI is a test that is used to detect areas of reduced blood flow to the heart muscle. It’s usually performed under both rest and stress conditions and then the physicians compare the two images to determine if the patient has significant CAD.

SPECT is the most common modality used for MPI, but recently PET has been increasingly used for cardiovascular imaging. Some of the advantages it offers over SPECT are higher spatial and contrast resolution, higher image quality, improved diagnostic accuracy, accurate attenuation correction, and risk stratification.

The multi-center, international study that spanned the U.S., Canada and Finland enrolled about 800 patients with known or suspected CAD who were scheduled for coronary angiography and conventional SPECT. Out of those patients, 413 obese patients with a BMI above 30 underwent rest and stress flurpiridaz F 18 PET and SPECT imaging and coronary angiography.

The researchers found that flurpiridaz F 18 PET imaging had greater sensitivity — 71.1 percent — than SPECT — 51.7 percent — and similar specificity — 79.8 percent for PET and 77.5 percent for SPECT. In addition, a significantly higher percentage of flurpiridaz F 18 PET images were rated either excellent or good quality compared with SPECT images.

Notably, the radiation exposure associated with flurpiridaz F 18 PET imaging was reduced to less than 50 percent of the radiation associated with standard SPECT imaging.

Since it has a half life of 110 minutes, flurpiridaz F 18 can be used in conjunction with treadmill exercise, which is not feasible with other PET agents for MPI.

Lantheus is supposed to start the second phase of the trial with a revised protocol in place under an FDA-approved special protocol assessment. The company is also in active discussion with prospective strategic partners to complete the development and commercialization of flurpiridaz F 18.

In the future, Bateman thinks that flurpiridaz F 18 PET imaging may become the standard of care for obese patients with CAD.

“The current study provides important data concerning image quality, interpretive certainty, and diagnostic accuracy in a population of very obese people,” he said. “At this time, there is no great imaging test for obese people. This product has high likelihood for being the imaging test of choice for this large segment of the population.”

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