Ge mr750 3t scanner

All studies (n = 6 subjects) were performed on a 3T GE MR750 scanner (GE Healthcare, Waukesha, WI) with a 32-channel head coil (Nova Medical, Wilmington, MA). All experiments were conducted in accordance with the local Institutional Review Board (IRB), and all subjects were provided written informed consent. We implemented the OSSI pulse sequence using the vendor’s pulse programming language, EPIC, as well as our own in-house pulse sequence development framework, TOPPE [11 (link)]. Single slice imaging with was performed using a single shot constant-density spiral out trajectory (n_c = 6, TR = 17.5 ms, FA = 10^◦, FOV=19 × 19 cm², matrix = 45 × 45 reconstructed at 64 × 64, slice thickness = 2.5 mm, sampling BW = 250 kHz), with 16 extra k-space center samples prior to readout. Spatial distortions due to B₀ field inhomogeneity were corrected using a separately acquired field map.
Subjects were presented with a visual stimulus composed of right- and left-hemifield counter-phased 10Hz flickering checkerboards in 40-second blocks, repeated 6 times (240 seconds). The subject was instructed to gaze at a fixation cross in the center of their visual field during the experiment.

Each participant underwent a structural magnetic resonance imaging
(MRI) scan (GE MR 750 3T scanner, GE Healthcare, Port Washington, NY), in
some cases on a separate day, for coregistration and region-of-interest
analysis.

To find the optimal calibration size for auto-calibrated estimation of sensitivity maps and estimate the relative signal-to-noise ratio (SNR), fully-sampled wave-encoded k-space and fully-sampled Cartesian k-space were acquired with a quality-assurance phantom on a GE MR750 3T scanner (GE Healthcare, Waukesha, WI) using an 8-channel cardiac coil and a 3D spoiled gradient echo (SPGR) acquisition sequence. The acquisition parameters for this sequence are shown in Table 1. The sensitivity maps for wave-encoding were estimated with different sizes of wave-encoded calibration k-space (8×8 to 96×96) using the proposed auto-calibration method. Since the phantom remains static during the entire scan, the sensitivity maps estimated from the Cartesian k-space were used as the reference. The normalized root-mean-squared error (nRMSE) between the sensitivity maps for wave-encoding and Cartesian acquisition was used as a metric for determining the optimal calibration size. Another set of simulated wave-encoded k-space generated from the Cartesian k-space was also tested in the same manner to exclude the influence of wave-PSF estimation error. The SNR of fully-sampled images was estimated using the pseudo random replicas approach (40 (link)).