Ceretec

Less than 24 hours prior to each SPECT scan a ⁹⁹Mo generator was eluted. Approximately 1,85 GBq ^99mTcO₄ was added to the exametazime (d,1 hexamethylpropylene amine oxime (HMPAO); Ceretec®, GE Healthcare LTD, UK).

A SPECT scan was obtained by a nuclear medicine physician for every patient during follow-up. The procedure used was as follows. The patients received an injection of 740 MBq of [^99mTc]ethyl cysteinate dimer (Neurolite; Lantheus Medical Imaging, North Billerica, MA, USA) (eight patients received 740 MBq of [^99mTc]exametazime Ceretec; GE Healthcare, Little Chalfont, UK). The image acquisition began 15 minutes after injection with a dual-head gamma camera (Siemens Medical Imaging, Hoffman Estates, IL, USA) equipped with a fan beam collimator specially manufactured for the study of the brain. Patients were imaged while in the supine position. The heads of the gamma camera were 15 cm away from the center of rotation. The height of the table was 20 cm. Image acquisition included 32 tomographic projections of 50 seconds each. The acquisition matrix was 128 × 128 pixels with zoom set at 1.23. The acquisition window was focused on the energy of the ^99mTc isotope photopeak (that is, 140 keV) with a window width of 15%.

The labelling of autologous WBCs with prepared ^99mTc-HMPAO (Ceretec; GE Healthcare, Oslo, Norway) was based on previously published consensus papers and guidelines with adjustments to the local needs^{31 (link)}. WBC SPECT/CT was performed on a dedicated hybrid dual-head SPECT/CT scanner (Symbia Intevo, Siemens Medical Solutions, IL) using a low-energy high-resolution, parallel hole collimator 4 h after the intravenous injection of 740 MBq ^99mTc-HMPAO-labeled WBCs. SPECT was acquired at 64 stops per detector (angle of 2.813°) at 25 s/stop. CT was performed without using a contrast agent with a 16-slice helical CT scanner, and the images were reconstructed into 0.75-mm slices (130 kV, 100 mA in the Auto-mA mode, and pitch 1.2). CT-based attenuation-corrected SPECT and quantitative SPECT were reconstructed on 256 × 256 matrices using Flash 3D-ordered subset expectation maximization and an ordered subset conjugate gradient maximization (xSPECT Quant, Siemens Medical Solutions, IL) algorithms (eight subsets and four iterations; Gaussian filter of 8.0), respectively. Finally, the SPECT and CT images were co-registered as fusion SPECT/CT images.

During 4 weeks, the pigs underwent four brain-imaging sessions each to investigate the brain metabolism following oral and/or duodenal stimulations with sucrose. The brain imaging modality used to investigate cerebral blood flow (CBF) was the SPECT of technetium-99m (^99mTc, CIS Bio International, France) coupled with hexamethyl-propylene-amine-oxime (HMPAO, Ceretec, GE Healthcare, Velizy, France).