A combined Compressed Sensing Super-Resolution Diffusion and gSlider-SMS acquisition/reconstruction for rapid sub-millimeter whole-brain diffusion imaging
Lipeng Ning1,2, Kawin Setsompop2,3, and Yogesh Rathi1,2

1Brigham and Women's Hospital, Boston, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Massachusetts General Hospital, Boston, MA, United States

Synopsis

We introduce a new method for rapid acquisition of sub-millimeter whole-brain diffusion imaging. Our method combines the gSlider-SMS acquisition method and the compressed-sensing super-resolution reconstruction algorithm. We demonstrate that this proposed approach is able to increase the resolution to 860μm iso in an effective acquisition time of 12 min.

Purpose

Submillimeter isotropic diffusion imaging (DI) is made difficult by long acquisition time and low SNR. Slider-SMS acquisition1 has recently been proposed to provide large improvement to SNR efficiency for DI, by allowing a large number of imaging slices to be acquire simultaneously through the combined use of SMS parallel imaging and super-resolution approaches. Further improvement to this acquisition with a new generalized Slider approach (gSlider) is also being proposed2, which utilizes RF encoding to improve the orthogonality of the slice-encoding basis for super-resolution, to enable high quality 5 simultaneous slice super-resolution, which when combines with SMS parallel imaging can achieve highly efficient 10 simultaneous slices DI (gSlider x MB = 5x2). In this work, we provide further improvement to this acquisition by incorporating the framework of Compressed Sensing for Super-Resolution Diffusion (CS-RSD) proposed in3 to gSlider-SMS. This enables acquisition acceleration through under-sampling of the gSlider slice-encoded super-resolution acquisitions needed for super-resolution reconstruction of each diffusion direction (with different random undersampling for different diffusion directions). Such acquisition undersampling is made possible through sparsity enforce reconstruction where the diffusion signal in each voxel of the final high-resolution image is enforced to be sparse in the basis of spherical ridgelets. We demonstrate that the incorporation of the CS-RSD approach enables a further 2x efficiency gain to an already highly efficient 10 simultaneous slice gSlider-SMS acquisition. This permits, for the first time, high quality 860μm whole-brain DI at high b-value to be perform in a relevant clinical timeframe of 8 minutes.

Method

gSlider-SMS data with 10 simultaneous slice acquisition (gSlider×MB = 5×2) were acquired in a healthy volunteer on the 3T CONNECTOM system using custom-built 64-channel array. Imaging parameters were: 860μm iso; FOV 220×163.4×130 mm3; p.f. 6/8; TE = 64ms and TR per thick-slice volume = 4.2s; effective echo spacing = 0.32ms, 64 directions at b=2000 s/mm2 with interspersed b0 every 10 volumes, where for each diffusion direction, imaging were performed 5 times for different RF gSlider encoding, total scan-time ~25 min. Background phase removal was performed using real value diffusion algorithm4. Reconstruction for full sampled Slider encoding data were performed using Tikhonov regularized super-resolution reconstruction to represent fully-sampled acquisition for comparison. For incorporation of CS-RSD, the 5 different gSlider slice-encode imaging per diffusion direction were randomly undersampled to provide 2x acceleration to result in an effective acquisition time of ~12 min. This accelerated acquisition is reconstructed using algorithm proposed in3 and compared with the fully sampled reconstruction.

Results

Figure (1) shows the acquired thick-slice images and the reconstructed high-resolution diffusion-weighted images obtained using the Tikhonov regularization and the compressed-sensing approach, respectively. The high-resolution image obtained using the compressed-sensing approach has the lowest noise level due to the sparse representation using spherical ridgelets. Figure (2) shows the glyph results in a cortical gray-matter region of the three diffusion MRI volumes, respectively, with color-coded by the principle direction of the underlying diffusion tensors. The glyphs obtained using the compressed-sensing method have a similar pattern as in the result given by the Tikhonov regularization.

Acknowledgements

The authors would like to acknowledge the following grants from the National Institutes of Health which supported this work: R01MH099797 (PI: Rathi), R00EB012107 (PI: Setsompop).

References

1) K. Setsompop, B. Bilgic, A. Nummenmaa, Q. Fan, S. F. Cauley, S. Huang, I. Chatnuntawech, Y. Rathi, T. Witzel, L.L.Wald; SLIce Dithered Enhanced Resolution Simultaneous MultiSlice (SLIDER-SMS) for high resolution (700 μm) diffusion imaging of the human brain. In: Proc Intl Soc Mag Reson Med. ; 2015. p. 339.

2) K. Setsompop, J. Stockmann, Q. Fan, T. Witzel, L.L. Wald; Generalized SLIce Dithered Enhanced Resolution Simultaneous MultiSlice (gSlider-SMS) to increase volume encoding, SNR and partition profile fidelity in high-resolution diffusion imaging. submitted ISMRM 2016

3) L. Ning, K., Setsompop, O. Michilovich, N. Makris, M. E. Shenton, C.-F. Westin, and Y. Rathi; A joint compressed-sensing and super-resolution approach for very high-resolution diffusion imaging, NeuroImage, 2015.

4) C. Eichner,S.F. Cauley, J. Cohen-Adad, H. E. Möller, R. Turner, K. Setsompop,L. L. Wald; Real diffusion-weighted MRI enabling true signal averaging and increased diffusion contrast, NeuroImage, 2015.

Figures

The left and right columns show the color-coded diffusion tensor images and the diffusion-weighted images from one acquired thick-slice data set and the reconstructed high-resolution diffusion-weighted image volumes obtained using the Tikhonov regularization and the compressed-sensing approach, respectively.

The subfigures show the glyph results from the three diffusion-weighted images volumes, respectively, from a cortical gray-matter region indicated by the rectangle of the FA image. The colors of the glyphs indicate the principle directions of the underlying diffusion tensors




Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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