Synthesis and PET Imaging of 18F-NOS

The PET radiotracer ¹⁸F-NOS was synthesized as previously described (28 (link)). Participants were scanned with an Ingenuity PET/CT scanner (Philips Healthcare), which has a PET spatial resolution of 5 mm in full width at half maximum and an 18-cm axial field of view (34 (link)). For each scan, a nuclear medicine physician determined the thoracic field of view that best included the heart and lungs. After a low-dose attenuation-correction CT scan, a 1-h PET dynamic acquisition was started at the time of an intravenous bolus injection of ¹⁸F-NOS (199 ± 27 MBq) with the following framing schedule: 24 × 5 s, 6 × 10 s, 3 × 20 s, 2 × 30 s, 5 × 60 s, and 10 × 5 min. On the basis of published effective dose estimates of 15.9 μSv/MBq for ¹⁸F-NOS, 199 MBq delivers an effective dose of 3.16 mSv, with a maximum critical dose to the urinary bladder wall of 19.0 mSv (28 (link)). The attenuation-correction CT images were reconstructed into PET images using a previously described list-mode, blob-based ordered-subsets maximum-likelihood expectation-maximization algorithm, including flight-time and physical-data corrections (34 (link)). The radiologist who reviewed the images was masked to participant group status, as was the data analyst.