Ecat exact hr camera

All subjects underwent PET imaging with [¹¹C] PiB at Lawrence Berkeley National Laboratory on a Siemens ECAT EXACT HR camera (N = 66) or a Siemens Biograph PET/CT scanner (N = 1) as described in a previous study (Villeneuve et al., 2015 (link)). Approximately 15 mCi of [¹¹C] PiB was injected intravenously. The imaging protocol varied depending on study, but all subjects had images collected at t = 50–70 min post-injection except for one, who had data acquired between t = 55–70 min. PET frames were realigned, co-registered to the subject’s MP-RAGE MRI sequence, then normalized to mean activity in the cerebellar gray matter in order to generate Standardized Uptake Value Ratios (SUVR) images (Villeneuve et al., 2015 (link)).

During the whole procedure, lighting maintained at low intensity in a quiet room. Each PET scan was made in 3D mode (63 planes, axial field of view of 15.5 cm) using an ECAT Exact HR + camera (CTI-Siemens, USA) with a spatial resolution of 4 to 5 mm full width at half maximum (FWHM) in all three directions. For the scan, the radiotracer H₂¹⁵O was used to measure cerebral blood flow (CBF). Per scan, 500 MBq of activity dissolved in 32 mL of 0.9% saline was administered intravenously into the right forearm at 8 mL/s. After injection of the radiotracer, data were collected over 120 s. Consecutive scans were made with intervals of 10–15 min, resulting in a 2.5–3 h procedure. The participants were asked to keep their eyes closed during the scanning period, and their head was maintained in a steady position using a head-restraining adhesive band. Small movements of the head were manually corrected between scans using landmarks drawn on the face. A scan-specific attenuation correction was calculated to minimize inter-scan displacement induced variance (Reinders, 2002 (link)). Data acquisition involved reconstruction using a filtered back projection procedure, corrected for background radiation, and a final frame of 120 s was obtained. The rCBF was defined as the blood flow to a specific region of the brain in a given time, and was assumed to mirror the neural activity.