64-slice SPECT/CT provides cardiac imaging trifecta

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A prospective study conducted by Zohar Keidar, MD, and colleagues in the department of nuclear medicine at Rambam Health Care Campus and Faculty of Medicine, Technion, in Haifa, Israel, demonstrated that myocardial perfusion imaging may play an important role in determining the need for revascularization in patients with extensive vascular calcifications. The study was presented at the 93rd annual meeting of the Radiological Society of North America (RSNA) this week in Chicago.

A total of 50 patients who presented with chest pain underwent a rest/stress SPECT/CT with coronary calcium scoring as part of a study that evaluated the relationship between the coronary calcium score (CCS) and the presence of clinically significant lesions.

“Coronary plaque and associated coronary calcifications may demonstrate only a weak correlation with the extent of arterial stenosis,” wrote the study authors in a scientific poster presentation. “The degree of vascular stenosis caused by the atherosclerotic plaque is related to individual variations in coronary artery remodeling.”

The patient cohort, with confirmed or suspected ischemic heart disease, underwent a single-session hybrid imaging including myocardial SPECT perfusion imaging with Tc-hexakis-2-methoxyisobutylisonitrile (Tc-MIBI) and 64-slice CT coronary angiography (CTCA) including CCS measurement using an experimental device, the Ventri-VCT by GE Healthcare.

The authors reported that fused SPECT/CTCA images were used to detect clinically significant lesions potentially requiring catheterization, which they defined as a reversible perfusion defects demonstrated on SPECT in a territory showing a >50 percent stenosis detected on CTCA.

The patients were divided into subgroups according to their Agatston scores—derived on the basis of their CCS measurement. Of the 50 patients participating in the study, 26 had a CCS of <100 (17 had an Agatston score of 0-10 and 9 had a score of 11-100) and none of them showed clinically significant coronary lesions, according to the authors.

Of the remaining 24 study participants, 12 had a CCS of 101-400. From this group, seven patients showed normal coronaries on CTCA and two patients showed normal perfusion. The result was that 75 percent (9 patients) of the CCS 101-400 group demonstrated no clinically significant lesions.

A CCS score less than 400 indicates the strong likelihood of coronary artery disease. In the remaining 12 patients in the study group who had a CCS less than 400, CTCA demonstrated coronary lesions in 11 patients; however, this was associated with normal myocardial perfusion in six patients, for a total of seven of the 12 patients (58 percent) with no clinically significant coronary lesions.

“Since it has been shown that functionally insignificant coronary lesions do not benefit from revascularization procedures, our current study demonstrates that assessment of myocardial perfusion is paramount in determining the need for revascularization in patients with extensive vascular calcifications associated with the presence of a high CCS,” the authors wrote.