Page 95 - Bladder Dysfunction in the Context of the Bladder-Brain Connection - Ilse Groenendijk.pdf

Single subject and group whole-brain fMRI mapping of male genital sensation at 7 Tesla 93
is a good alternative for human touch7,45 and can comfortably be executed while stand- ing at the entrance of the scanner bore. Subjects were given a towel which they were instructed to place on the abdomen. Subsequently, subjects were instructed to place the penis on the towel in order to prevent skin-to-skin contact with the thigh and ab- domen during the tactile stimulation. Prior to the actual scanning session, all subjects underwent a training session in a mock scanner. This gave subjects the opportunity to get acquainted with the tactile stimulus (brushing of a toothbrush). During this training session, tactile stimulation was delivered in a similar manner as described above.
Data acquisition
All functional and structural data were acquired on a 7T MRI scanner (Philips Achieva) using a volume transmit coil and a 32-channel receive coil (Nova Medical). Functional data was acquired using a multiband echo planar imaging (mb-EPI) sequence with multiband factor 2. Whole-brain coverage, including the anterior lobe of the cerebellum, was achieved using the following parameters: voxel size 1.77 x 1.77 x 1.75 mm3; matrix size: 104 x 127; FOV = 184x223 mm2; number of slices: 70; TR/TE = 2000/25 ms; flip angle = 70°; in-plane SENSE factor R = 3. Whole-brain anatomical data was acquired using the MPRAGE sequence with the following parameters: voxel size 0.7 x 0.7 x 0.7 mm3, matrix size: 352 x 353, FOV = 246 mm; number of slices: 249; TR/TE = 4.4/1.97 s, SENSE factors R = 1.6 (anterior-posterior) and R = 1.5 (right-left); total acquisition time 8’35”. In addition, to account for signal loss in infratentorial areas, a dielectric pad containing calcium titanate (CaTiO3)46 was placed posterior of the subjects’ heads.46
Image preprocessing
All data was reconstructed on an offline workstation using dedicated reconstruction software (ReconFrame, Gyrotools, Zürich, Switzerland). Further data processing was done in SPM12 (Wellcome Trust Center for Neuroimaging, London, UK). Pre-processing steps included joint image realignment of all four functional runs, co-registration of the anatomical image to the resulting mean functional image and smoothing of functional data with a Gaussian kernel (FWHM 2.5 mm). For the extraction of peak activation coor- dinates, functional data was normalized to the standardized brain template of the Mon- treal Neurological Institute (MNI). Additionally, inflated cortical surfaces were created in Freesurfer (http://surfer.nmr.harvard.edu/) using single subject anatomical images and the MNI template. In order to aid the inflation process, all images were first bias corrected (bias FWHM = 18, sampling distance = 2) and resliced to 1mm isotropic in SPM.
Whole-brain analyses
First level statistical analysis was conducted using the General Linear Model (GLM). Each functional task was modeled as a boxcar convolved with a canonical hemodynamic re-
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