Development of a reproducible FDG PET/CT cardiac imaging protocol for the evaluation of cardiac sarcoidosis

Objectives FDG-PET imaging has proven to have potential for detecting cardiac sarcoidosis. The purpose of this study is to evaluate our protocol and propose the optimal scan parameters for FDG PET scanning for cardiac sarcoidosis.

Methods 15 patients with suspected cardiac sarcoid were studied. All ate a high protein, high fat, no carbohydrate meal the night before their PET scan with a subsequent minimum 12 hour fast to suppress physiologic heart uptake. A resting 10 mCi Myoview cardiac perfusion SPECT scan was acquired first. Whole body PET/CT was acquired 45-60 minutes post injection of 12 mCi (+/- 20%) of FDG followed by a single bed position over the heart for 15 minutes. Image interpretation was prospective consisting of SUV analysis of the myocardium, visual interpretation, comparison to resting cardiac SPECT and whole body FDG PET/CT. Biopsy results, post-therapy follow-up, and clinical follow-up consensus review with cardiologists served as validation of results.

Results Of 15 patients, 10 had no cardiac FDG uptake and were interpreted as negative with SUVmax 1.8 +/- 0.3 in the myocardium. Five patients exhibited increased focal/nodular uptake which was interpreted as positive. The ratio of SUVmax in the focal areas to suppressed myocardium is 10 +/- 5 to 1.8 +/- 0.27. Three of the positive patients had known sarcoidosis in distant regions prior to the whole body scan. Two of the positive patients had sarcoidosis localized to the heart only. Abnormal SPECT perfusion did not correlate to positive FDG PET. Also, negative SPECT did not completely correlate to negative FDG PET.

Conclusions Our dedicated cardiac PET/CT protocol appears effective for suppressing native myocardial FDG uptake in order to detect active cardiac sarcoid lesions and follow-up PET/CT consistently shows post-therapeutic response to steroid treatment. In our pilot data cohort, the resting cardiac perfusion SPECT and whole body PET/CT did not appear to provide significant useful adjunctive clinical information and may potentially be eliminated from our procedure in the future.