PET. The PET studies were performed with an ECAT
EXACT (CTI, Knoxville, Tennessee) scanner, which allows
simultaneous acquisition of 47 contiguous transaxial images,
with a total axial field of view of 16.2 cm. The resolution of the
scanner was 4.8 0108 0.6 mm in the axial direction and
6.1 0108 0.2 mm in the transaxial planes. A transmission
scan was obtained for 15 min to allow for attenuation
correction with retractable germanium-68 ring sources. For
emission studies, the tracers used were N-13 ammonia
(NH3) (10 MBq/kg) to assess resting perfusion and FDG
(4 MBq/kg) to assess glucose use; FDG was injected 45 min
after oral glucose loading (50 g). The emission scans were
started 4 min after injection of NH3 and 45 min after FDG
injection. Data acquisition lasted 15 min for both tracers.
Short-axis and vertical and horizontal long-axis slices
(thickness 0.8 cm each) were reconstructed with a Hanning
filter (cut-off 1.18 cycle/cm) and corrected for attenuation.
Both studies were performed on the same day in all of the
patients: first, the N13-ammonia study, followed by the
FDG study 2 h later.