8 channel head receiver coil

The MRI data were obtained on a GE Discovery MR750 3.0T MR scanner (GE Healthcare, Waukesha, WI, USA) with an 8-channel head receiver coil. The routine MRI was initially performed to exclude subjects with brain and spinal abnormalities. High-resolution 3D T1-weighted images were acquired using a brain volume (BRAVO) sequence with parameters as follows: repetition time (TR) = 8.2 ms, echo time (TE) = 3.2 ms, inversion time (TI) = 450 ms, matrix size = 256 × 256, field of view (FOV) = 256 mm × 256 mm, flip angle = 12°, slice thickness = 1 mm, and 176 slices with no gap. The resting-state functional MRI (fMRI) images were obtained using a single-shot gradient-echo echo-planar imaging sequence: TR = 2,000 ms, TE = 30 ms, flip angle = 90 degree, matrix = 64 × 64, FOV = 22 × 22 cm, slice thickness =3.4 mm, gap = 1.0 mm, 33 slices, interleaved transverse slices, and 210 volumes. All subjects were asked to keep awake with eyes closed and heads static during the fMRI scan. One patient with chronic LHON and one sighted control were excluded from the imaging analysis due to poor MRI data quality.

All subjects were imaged using a research-dedicated 3T MRI system (MR750, GE Healthcare, Waukesha, WI) equipped with an 8-channel head receiver coil and peripherals for recording cardiac and respiratory signals (photoplethysmograph and bellows, respectively). The protocol consisted of initial localizer images followed by IR-FSPGR (inversion recovery prepared fast spoiled gradient echo) T1-weighted axial anatomical imaging (repetition time (TR)/echo time (TE)/flip angle (Ɵ)) = 82 ms/3.2 ms/8 degrees); field of view (FOV) = 22 cm × 22 cm; 190 slices; slice thickness = 1 mm) and fMRI using repeated spiral in/out T2*-weighted imaging (TR/TE/Ɵ = 2000 ms/30 ms/70 degrees; FOV = 20 cm × 20 cm; 30 slices; slice thickness = 4.5 mm) to record BOLD hemodynamic responses to neural activity effect [19 (link)]. During the 1-hour imaging session, patients performed a battery of up to three behavioral tests in duplicate, with a 20 minute test-retest interval time; identical procedures were used for the matched healthy controls. The randomized battery consisted of a hand motor task (“hand squeezing”), a rhyming task [20 (link)] and a written phonemic fluency task [21 (link)], as described below.

Anatomical T1-weighted and functional T2*-weighted MR images were acquired with a 3-Tesla General Electric scanner equipped with an 8-channel receiver head coil. Functional images were acquired using a T2*-weighted gradient-echo, echo-planar (EPI) pulse sequence (acceleration factor asset = 2, 40 sequential transverse slices covering the whole brain, with a Repetition Time (TR) time of 2.5 sec, Echo Time (TE) = 30 msec, flip angle = 90°, Field of View (FOV) = 205 × 205 mm², inter-slice gap = 0.5 mm, slice thickness = 3 mm, in-plane resolution = 2.5 × 2.5 × 2.5 mm³). At the end of the six functional runs, a T1-weighted anatomical scan (acceleration factor arc = 2, 156 sagittal slices, matrix 256 × 256, isotropic resolution 1 × 1 × 1 mm³, Time to Invert (TI) = 450 msec, TR = 8100 msec, TE = 3.2 msec, flip angle = 12°) was acquired for each participant.