Ecat exact hr pet scanner

Fibrillar cortical amyloid burden was measured using Pittsburgh Compound B (PiB)- positron emission tomography (PET) imaging conducted at the Massachusetts General Hospital (MGH) PET facility. C11-PiB synthesis and imaging, using a Siemens ECAT EXACT HR+ PET scanner, were performed as previously reported.[36 (link)–39 (link)] PiB distribution volume ratio (DVR) was calculated for an aggregate of cortical regions that typically have elevated PiB retention in AD dementia, including frontal, lateral temporal, and lateral and medial parietal regions. Amyloid classification was determined using the aggregate PiB DVR value as previously described.[40 (link)] Using a Gaussian mixture modeling approach amyloid-positive or amyloid-negative status was based on a cut off value of 1.20 that was determined using a portion of participants included in the current analysis (N=161).

A Siemens ECAT EXACT HR + PET scanner was used to collect beta-amyloid using the C11-PIB tracer. Before injection, 10-min transmission scans for attenuation correction were collected. After injection of 8.5–15 mCi PIB, 60-min of dynamic data were acquired in 3D acquisition mode. Data were manually evaluated and corrected for motion. Then, a mean image was created by averaging across the first 8 min of data acquisition and used for co-registration. Each PET image was coregistered to that subjects T1 Freesurfer processed structural image and mapped into native PET space. The native space labels were then used to make ROI measurements computed using the Logan plot method with cerebellar grey matter as the reference region. The same atlas for extracting cortical thickness was used to extract mean DVR values from ROIs (i.e., the Desikan-Killiany atlas). Specifically, left and right precuneus ROIs were extracted as a proxy measure for beta-amyloid load. This region was chosen because it accumulates beta-amyloid early in AD (Jagust, 2009 (link)), shows reliable PIB binding (Mintun et al., 2006 (link); Rowe et al., 2007 (link)), has high inter-rater reliability (Rosario et al., 2011 (link)), and has been found to be highly correlated with ability discrepancy scores (McDonough et al. 2016 (link)). Descriptive statistics for the beta-amyloid can be found in Table 1.

All PET imaging was performed using a Siemens ECAT Exact HR+ PET Scanner (Siemens Molecular Imaging, Knoxville, TN). LV sympathetic innervation was assessed using PET measures of the regional myocardial retention of [¹¹C]HED, as previously described.^{19 (link)} A ‘retention index’ (RI; mL blood min⁻¹ mL⁻¹ tissue) was generated for each sector by normalizing the measured tissue concentration of [¹¹C]HED in the final image frame to the time integral of the blood time-activity curve. The generated RI data were displayed in the standard cardiac ‘polar map’ format. A z-score analysis of the regional RI values was performed to obtain measures of the regional heterogeneity of [¹¹C]HED retention in the subjects.^{19 (link)} All analyses were performed by a single investigator (DR) who was masked to subjects’ clinical and laboratory data.
The myocardial kinetics of [¹¹C]acetate were used to assess LV oxidative metabolism and resting myocardial perfusion. LV measurements obtained from cardiac magnetic resonance (CMR) imaging were used to subsequently calculate LV efficiency.
The pre-specified primary measures for CAN were the global mean [¹¹C]HED RI and measures of HR variability.