Hybrid Magnetic Resonance Imaging and Positron Emission Tomography With Fluorodeoxyglucose to Diagnose Active Cardiac Sarcoidosis

Abstract

OBJECTIVES The purpose of this study was to explore the diagnostic usefulness of hybrid cardiac magnetic resonance (CMR) and positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) for active cardiac sarcoidosis. BACKGROUND Active cardiac sarcoidosis (aCS) is underdiagnosed and has a high mortality. METHODS Patients with clinical suspicion of aCS underwent hybrid CMR/PET with late gadolinium enhancement (LGE) and FDG to assess the pattern of injury and disease activity, respectively. Patients were categorized visually as magnetic resonance (MR)+PET+ (characteristic LGE aligning exactly with increased FDG uptake), MR+PET− (characteristic LGE but no increased FDG), MR−PET− (neither characteristic LGE nor increased FDG), and MR−PET+ (increased FDG uptake in absence of characteristic LGE) and further characterized as aCS+ (MR+PET+) or aCS− (MR+PET−, MR−PET−, MR−PET+). FDG uptake was quantified using maximum target-to-normal-myocardium ratio and the net uptake rate (Ki) from dynamic Patlak analysis. Receiver-operating characteristic methods were used to identify imaging biomarkers for aCS. FDG PET was assessed using computed tomography/PET in 19 control subjects with healthy myocardium. RESULTS A total of 25 patients (12 males; 54.9 ± 9.8 years of age) were recruited prospectively; 8 were MR+PET+, suggestive of aCS; 1 was MR+PET−, consistent with inactive cardiac sarcoidosis; and 8 were MR−PET−, with no imaging evidence of cardiac sarcoidosis. Eight patients were MR−PET+ (6 with global myocardial FDG uptake, 2 with focal-on-diffuse uptake); they demonstrated distinct Ki values and hyperintense maximum standardized uptake value compared with MR+PET+ patients. Similar hyperintense patterns of global (n = 9) and focal-on-diffuse (n = 2) FDG uptake were also observed in control patients, suggesting physiological myocardial uptake. Maximum target-to-normal-myocardium ratio values were higher in the aCS+ group (p < 0.001), demonstrating an area under the curve of 0.98 on receiver-operating characteristic analysis for the detection of aCS, with an optimal maximum target-to-normal myocardium ratio threshold of 1.2 (Youden index: 0.94). CONCLUSIONS CMR/PET imaging holds major promise for the diagnosis of aCS, providing incremental information about both the pattern of injury and disease activity in a single scan. (In Vivo Molecular Imaging [MRI] of Atherothrombotic Lesions; NCT01418313)

Dynamic whole-body PET imaging: principles, potentials and applications

“…The first assumption can be especially invalid in earlier scan times, in less FDG-avid tumors, or in the presence of substantial blood volume. Moreover, a high physiologic (non-specific) uptake may also interfere with disease-specific uptake in the same tissue, for example when patients fail to adhere to special diet prior to the PET exam [84]. The second assumption can also be invalid.…”

A case of cardiac sarcoidosis mimicking cardiac amyloidosis on cardiovascular magnetic resonance

“…13 In particular, cardiac positron emission tomography-magnetic resonance imaging is reported to be clinically feasible for the detection of cardiac inflammation such as active CS. 14,15 A combination of positron emission tomography and CMR may be more desirable in non-invasive imaging for CS to differentiate it from other types of cardiac hypertrophy.…”

Advanced cardiovascular imaging for the evaluation of cardiac sarcoidosis

“…The authors prospectively investigated 25 patients with clinical suspicion of CS on a hybrid PET-MR system. 52 They observed that eight patients had neither characteristic sarcoid LGE nor increased FDG uptake, and the diagnosis of CS was then unlikely. In contrast, eight out of nine patients with characteristic sarcoid LGE pattern also had focally increased myocardial FDG uptake matching the location of LGE.…”