Ecat hrrt

FDG-PET was performed under standard conditions with an average dose of 185 MBq FDG on a 24-detector ring high-resolution research tomograph (ECAT HRRT, Siemens) and preprocessed in SPM12 (http://www.fil.ion.ucl.ac.uk/spm/software/spm12) running on MATLAB R2018a (The MathWorks, Inc.). Image acquisition procedure and preprocessing have previously been described in detail [27 (link), 40 ]. FDG-PET acquisition was conducted in the medication OFF-state after at least 12-h discontinuation of levodopa, amantadine and MAO-inhibitors, and 72-h withdrawal from dopamine agonists. For the current analysis, normalized image dimensions were 91/109/91 voxels (x/y/z) sized 2 × 2 × 2 mm.

After the stimulation, the participants were transferred to a wheel chair and transported to the PET facility, while still wearing noise-cancellation earphones and sleep-goggles. Each participant was placed comfortably on the bed of the high-resolution PET system (ECAT HRRT; CTI/Siemens, Knoxville, TN, USA). The PET scan protocol has previously been reported (14 (link)). At 54 min post-injection, a 6 min transmission scan (Cs-137 point source) was performed. At exactly 60 min post-injection, the 60 min dynamic PET acquisition (12 × 5 min frames) was initiated. An ordered-subsets expectation maximization 3D algorithm was used to reconstruct the PET scans into image volumes consisting of 207 axial slices and a 1.22 mm voxel size. Frame-to-frame motion correction was made followed by summation of all frames into one static PET data volume. Reconstructed images were revised to detect dead time, random, and scatter events, and detector efficiency variations.

Isometric 1 mm T₁-weighted magnetic resonance imaging (MRI) was performed with a Skyra 3T system (Siemens, Erlangen, Germany).
¹¹C-PiB PET was performed with a High Resolution Research Tomograph (ECAT HRRT, CTI/Siemens, Knoxville, TN) according to a previously published scan protocol [1 (link)]. The pretreatment scans were performed at different time before treatment start, while the posttreatment scans all were performed on the day following the end of the light-therapy, i.e., on day 11. A mean dose of 407 ± 13.8 MBq (for poststimulation scans) and 424 ± 15.3 MBq (for the prestimulation scans) ¹¹C-PiB was injected, and list-mode PET was acquired for 40-90 minutes postinjection. Data was subsequently rebinned into five frames of 10 min each.

FDG-PET scans were acquired in 47 PD patients and 11 controls after overnight fasting in the OFF-state since it has been shown that the ON-state could alter neural functions in PD (Tahmasian et al., 2015 (link), 2017 (link)). Images were recorded on a Siemens high-resolution research tomograph (ECAT HRRT) with 207 transaxial image planes and a voxel size of 1.219 mm (isotropic) in 3D acquisition mode. Subjects lay comfortably in a supine position in a quiet room with dimmed light; a vacuum cushion was used to restrict head motion. Following a transmission scan for attenuation correction, 185 MBq 2-[fluorine-18]fluoro-2-deoxy-d-glucose were injected. Recording started 20 s after injection and continued for 60 min, with one frame saved every 10 min. Using software VINCI (Vollmar et al., 2003 ), frames were co-registered together; an average of frames 3–6 (minute 20–60) was generated and saved in the Nifti format for the following analysis.
High-resolution T1-weighted MRI scans, acquired on a 3T Siemens Magnetom Prisma with a voxel size of 0.9 × 0.9 × 0.9 mm³, were available for 43 of the 47 patients and the 11 controls who underwent FDG-PET. In PD patients, MRI scans were performed under regular dopaminergic medication to reduce head motion (Tahmasian et al., 2015 (link)).

PET data were acquired in a group of 7 CB participants (three males aged 41 ± 8 years) and 7 HEAC (aged 25 ± 5 years, four males; HAEC_DEN) using a Siemens ECAT HRRT at Rigshospitalet in Copenhagen, Denmark (Table 1). Participants' MRIs were acquired using a 3 T Siemens Trio MRI scanner at the Danish Research Centre for Magnetic Resonance, Hvidovre Hospital, Hvidovre, Denmark. Details of the scans have been published elsewhere [32 (link)]. One among the seven CB participants had limited vision at birth that progressed to complete blindness at the age of seven; all others were completely blind from birth. Structural MRI data were acquired (MP-RAGE, TR 1.5 s, TE 3.93 ms, inversion recovery time (TI) 0.8 s, 256 slices with no gap, 192 × 256 mm FOV, and 6 minutes 36 seconds). PET data were acquired forty minutes after bolus injection of approximately 210 MBq FDG (single frame, OSEM3D mode, 207 slices with no gap, 1.2 × 1.2 × 1.2 mm voxels, and 40 minutes). During the tracer uptake period, control participants were blindfolded and all participants rested in a dimly lit room without falling asleep.