| Summary: | <p><strong>Purpose:</strong> We investigate the use of TURBINE, a 3D radial-Cartesian acquisition scheme in which EPI planes are rotated about the phase-encoding axis to acquire a cylindrical k-space, for high-fidelity ultra-high isotropic resolution fMRI at 7T with minimal distortion and blurring.</p>
<p><strong>Methods:</strong> An improved, completely self-navigated version of the TURBINE sampling scheme was designed for fMRI at 7T. To demonstrate the image quality and spatial specificity of the acquisition, thin-slab visual and motor BOLD fMRI at 0.67 mm isotropic resolution (16 mm slab, TRvol = 2.32 s) and 0.8x0.8x2.0 mm (whole-brain, TRvol = 2.4 s) data were acquired. To prioritize the high spatial fidelity, we employed a temporally regularized reconstruction to improve sensitivity without any spatial bias.</p>
<p><strong>Results:</strong> TURBINE images provide high structural fidelity with almost no distortion, dropout or T2* blurring for the thin-slab acquisitions compared to conventional 3D EPI, owing to the radial sampling in-plane and the short echo train used. This results in activation that can be localized to pre- and post-central gyri in a motor task, for example, with excellent correspondence to brain structure measured by a T1-MPRAGE. The benefits of TURBINE (low distortion, dropout, blurring) are reduced for the whole-brain acquisition due to the longer EPI train. We demonstrate robust BOLD activation at 0.67 mm isotropic resolution (thin-slab) and also anisotropic 0.8x0.8x2.0 mm (whole-brain) acquisitions.</p>
<p><strong>Conclusion:</strong> TURBINE is a promising acquisition approach for high-resolution, minimally distorted fMRI at 7T and could be particularly useful for fMRI in areas of high B0 inhomogeneity.</p>
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