Signa excite 11

SPGRs were performed using a 1.5-Tesla MRI (Signa Excite 11.0, GE Medical Systems) with 1.2-mm slice thickness, field of view (FOV)=260×260 mm, number of excitation (NEX)=1, no interslice gap, TR=22 ms, TE=6 ms, and flip angle=30°. The images were saved in DICOM format and changed to an appropriate format for VBM using MRIcro. VBMs were performed using the SPM5 software (http://www.fil.ion.ucl.ac.uk/spm/software/spm5/). The procedures were as follows: Spatial normalization, modulation to compensate for voxel differences, tissue segmentation into gray matter, white matter and CSF, and finally smoothing with a 12-µL full-width at half-maximum Gaussian kernel for preprocessing. After image processing, voxel-based comparisons among the groups were made using two-sample t-tests between groups. Because mean age, gender, and educational levels were similar among the groups, only total intracranial volume (TIV), obtained automatically using SPM5, was used as a covariate. Only areas with voxel levels of P=0.005, uncorrected, were regarded as significant.

All PET images were acquired using combined PET/computed tomography (CT) in-line systems (Biograph TruePoint; Siemens Medical Solutions, Erlangen, Germany or Discovery 710D; GE Healthcare, Chicago, IL, USA). An average of 296 MBq ¹⁸F-florbetaben was injected intravenously, and the scan was initiated 90 minutes later. A low-dose CT scan was performed for attenuation correction and was immediately followed by PET in three-dimensional mode for 20 minutes. The subject's head was fixed using a head holder in order to minimize motion artifacts. The standard ordered subset expectation maximization algorithm (21 subsets with 3 iterations or 16 subsets with 4 iterations) was utilized for the reconstruction of PET images. All PET images were reviewed by nuclear medicine physicians who were blinded to the results of neuropsychological testing and successfully completed the electronic training program provided by the manufacturer. The result was dichotomized into amyloid positivity or negativity using visual assessments. The participants also underwent scanning on a 3.0-Tesla MRI device (Signa Excite 11.0, GE Medical Systems, Milwaukee, WI, USA) consisting of SWI and/or GRE T2-weighted imaging, as well as conventional T1-weighted, T2-weighted, and fluid-attenuated inversion recovery (FLAIR) sequences.