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Fernando E. Boada - One of the best experts on this subject based on the ideXlab platform.

  • high resolution Spiral imaging on a whole body 7t scanner with minimized image blurring
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Yongxian Qian, Tamer S. Ibrahim, Tiejun Zhao, Fernando E. Boada
    Abstract:

    High-resolution (∼0.22 mm) images are preferably acquired on whole-body 7T scanners to visualize minianatomic structures in human brain. They usually need long acquisition time (∼12 min) in three-dimensional scans, even with both parallel imaging and partial Fourier samplings. The combined use of both fast imaging techniques, however, leads to occasionally visible undersampling artifacts. Spiral imaging has an advantage in acquisition efficiency over rectangular sampling, but its implementations are limited due to image blurring caused by a strong off-resonance effect at 7T. This study proposes a solution for minimizing image blurring while keeping Spiral efficient. Image blurring at 7T was, first, quantitatively investigated using computer simulations and point-spread functions. A combined use of multishot Spirals and ultrashort echo time acquisitions was then employed to minimize off-resonance-induced image blurring. Experiments on phantoms and healthy subjects were performed on a whole-body 7T scanner to show the performance of the proposed method. The three-dimensional brain images of human subjects were obtained at echo time = 1.18 ms, resolution = 0.22mm (field of view = 220mm, matrix size = 1024), and in-plane Spiral shots = 128, using a home-developed ultrashort echo time sequence (acquisition-weighted stack of Spirals). The total acquisition time for 60 partitions at pulse repetition time = 100 ms was 12.8 min without use of parallel imaging and partial Fourier sampling. The blurring in these Spiral images was minimized to a level comparable to that in gradient-echo images with rectangular acquisitions, while the Spiral acquisition efficiency was maintained at eight. These images showed that Spiral imaging at 7T was feasible. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

  • High-resolution Spiral imaging on a whole-body 7T scanner with minimized image blurring
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Yongxian Qian, Yik Kiong Hue, Tamer S. Ibrahim, Tiejun Zhao, Fernando E. Boada
    Abstract:

    High-resolution (approximately 0.22 mm) images are preferably acquired on whole-body 7T scanners to visualize minianatomic structures in human brain. They usually need long acquisition time ( approximately 12 min) in three-dimensional scans, even with both parallel imaging and partial Fourier samplings. The combined use of both fast imaging techniques, however, leads to occasionally visible undersampling artifacts. Spiral imaging has an advantage in acquisition efficiency over rectangular sampling, but its implementations are limited due to image blurring caused by a strong off-resonance effect at 7T. This study proposes a solution for minimizing image blurring while keeping Spiral efficient. Image blurring at 7T was, first, quantitatively investigated using computer simulations and point-spread functions. A combined use of multishot Spirals and ultrashort echo time acquisitions was then employed to minimize off-resonance-induced image blurring. Experiments on phantoms and healthy subjects were performed on a whole-body 7T scanner to show the performance of the proposed method. The three-dimensional brain images of human subjects were obtained at echo time = 1.18 ms, resolution = 0.22 mm (field of view = 220 mm, matrix size = 1024), and in-plane Spiral shots = 128, using a home-developed ultrashort echo time sequence (acquisition-weighted stack of Spirals). The total acquisition time for 60 partitions at pulse repetition time = 100 ms was 12.8 min without use of parallel imaging and partial Fourier sampling. The blurring in these Spiral images was minimized to a level comparable to that in gradient-echo images with rectangular acquisitions, while the Spiral acquisition efficiency was maintained at eight. These images showed that Spiral imaging at 7T was feasible.

Yongxian Qian - One of the best experts on this subject based on the ideXlab platform.

  • high resolution Spiral imaging on a whole body 7t scanner with minimized image blurring
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Yongxian Qian, Tamer S. Ibrahim, Tiejun Zhao, Fernando E. Boada
    Abstract:

    High-resolution (∼0.22 mm) images are preferably acquired on whole-body 7T scanners to visualize minianatomic structures in human brain. They usually need long acquisition time (∼12 min) in three-dimensional scans, even with both parallel imaging and partial Fourier samplings. The combined use of both fast imaging techniques, however, leads to occasionally visible undersampling artifacts. Spiral imaging has an advantage in acquisition efficiency over rectangular sampling, but its implementations are limited due to image blurring caused by a strong off-resonance effect at 7T. This study proposes a solution for minimizing image blurring while keeping Spiral efficient. Image blurring at 7T was, first, quantitatively investigated using computer simulations and point-spread functions. A combined use of multishot Spirals and ultrashort echo time acquisitions was then employed to minimize off-resonance-induced image blurring. Experiments on phantoms and healthy subjects were performed on a whole-body 7T scanner to show the performance of the proposed method. The three-dimensional brain images of human subjects were obtained at echo time = 1.18 ms, resolution = 0.22mm (field of view = 220mm, matrix size = 1024), and in-plane Spiral shots = 128, using a home-developed ultrashort echo time sequence (acquisition-weighted stack of Spirals). The total acquisition time for 60 partitions at pulse repetition time = 100 ms was 12.8 min without use of parallel imaging and partial Fourier sampling. The blurring in these Spiral images was minimized to a level comparable to that in gradient-echo images with rectangular acquisitions, while the Spiral acquisition efficiency was maintained at eight. These images showed that Spiral imaging at 7T was feasible. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

  • High-resolution Spiral imaging on a whole-body 7T scanner with minimized image blurring
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Yongxian Qian, Yik Kiong Hue, Tamer S. Ibrahim, Tiejun Zhao, Fernando E. Boada
    Abstract:

    High-resolution (approximately 0.22 mm) images are preferably acquired on whole-body 7T scanners to visualize minianatomic structures in human brain. They usually need long acquisition time ( approximately 12 min) in three-dimensional scans, even with both parallel imaging and partial Fourier samplings. The combined use of both fast imaging techniques, however, leads to occasionally visible undersampling artifacts. Spiral imaging has an advantage in acquisition efficiency over rectangular sampling, but its implementations are limited due to image blurring caused by a strong off-resonance effect at 7T. This study proposes a solution for minimizing image blurring while keeping Spiral efficient. Image blurring at 7T was, first, quantitatively investigated using computer simulations and point-spread functions. A combined use of multishot Spirals and ultrashort echo time acquisitions was then employed to minimize off-resonance-induced image blurring. Experiments on phantoms and healthy subjects were performed on a whole-body 7T scanner to show the performance of the proposed method. The three-dimensional brain images of human subjects were obtained at echo time = 1.18 ms, resolution = 0.22 mm (field of view = 220 mm, matrix size = 1024), and in-plane Spiral shots = 128, using a home-developed ultrashort echo time sequence (acquisition-weighted stack of Spirals). The total acquisition time for 60 partitions at pulse repetition time = 100 ms was 12.8 min without use of parallel imaging and partial Fourier sampling. The blurring in these Spiral images was minimized to a level comparable to that in gradient-echo images with rectangular acquisitions, while the Spiral acquisition efficiency was maintained at eight. These images showed that Spiral imaging at 7T was feasible.

Zhipei Liang - One of the best experts on this subject based on the ideXlab platform.

  • variable slew rate Spiral design theory and application to peak b 1 amplitude reduction in 2d rf pulse design
    Magnetic Resonance in Medicine, 2007
    Co-Authors: Kevin F King, Zhipei Liang
    Abstract:

    A new class of Spiral trajectories called variable slew-rate Spirals is proposed. The governing differential equations for a variable slew-rate Spiral are derived, and both numeric and analytic solutions to the equations are given. The primary application of variable slew-rate Spirals is peak B(1) amplitude reduction in 2D RF pulse design. The reduction of peak B(1) amplitude is achieved by changing the gradient slew-rate profile, and gradient amplitude and slew-rate constraints are inherently satisfied by the design of variable slew-rate Spiral gradient waveforms. A design example of 2D RF pulses is given, which shows that under the same hardware constraints the RF pulse using a properly chosen variable slew-rate Spiral trajectory can be much shorter than that using a conventional constant slew-rate Spiral trajectory, thus having greater immunity to resonance frequency offsets.

  • variable slew rate Spiral design theory and application to peak b 1 amplitude reduction in 2d rf pulse design
    Magnetic Resonance in Medicine, 2007
    Co-Authors: Dan Xu, Kevin F King, Zhipei Liang
    Abstract:

    A new class of Spiral trajectories called variable slew-rate Spirals is proposed. The governing differential equations for a variable slew-rate Spiral are derived, and both numeric and analytic solutions to the equations are given. The primary application of variable slew-rate Spirals is peak B1 amplitude reduction in 2D RF pulse design. The reduction of peak B1 amplitude is achieved by changing the gradient slew-rate profile, and gradient amplitude and slew-rate constraints are inherently satisfied by the design of variable slew-rate Spiral gradient waveforms. A design example of 2D RF pulses is given, which shows that under the same hardware constraints the RF pulse using a properly chosen variable slew-rate Spiral trajectory can be much shorter than that using a conventional constant slew-rate Spiral trajectory, thus having greater immunity to resonance frequency offsets. Magn Reson Med 58:835–842, 2007. © 2007 Wiley-Liss, Inc.

Tamer S. Ibrahim - One of the best experts on this subject based on the ideXlab platform.

  • high resolution Spiral imaging on a whole body 7t scanner with minimized image blurring
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Yongxian Qian, Tamer S. Ibrahim, Tiejun Zhao, Fernando E. Boada
    Abstract:

    High-resolution (∼0.22 mm) images are preferably acquired on whole-body 7T scanners to visualize minianatomic structures in human brain. They usually need long acquisition time (∼12 min) in three-dimensional scans, even with both parallel imaging and partial Fourier samplings. The combined use of both fast imaging techniques, however, leads to occasionally visible undersampling artifacts. Spiral imaging has an advantage in acquisition efficiency over rectangular sampling, but its implementations are limited due to image blurring caused by a strong off-resonance effect at 7T. This study proposes a solution for minimizing image blurring while keeping Spiral efficient. Image blurring at 7T was, first, quantitatively investigated using computer simulations and point-spread functions. A combined use of multishot Spirals and ultrashort echo time acquisitions was then employed to minimize off-resonance-induced image blurring. Experiments on phantoms and healthy subjects were performed on a whole-body 7T scanner to show the performance of the proposed method. The three-dimensional brain images of human subjects were obtained at echo time = 1.18 ms, resolution = 0.22mm (field of view = 220mm, matrix size = 1024), and in-plane Spiral shots = 128, using a home-developed ultrashort echo time sequence (acquisition-weighted stack of Spirals). The total acquisition time for 60 partitions at pulse repetition time = 100 ms was 12.8 min without use of parallel imaging and partial Fourier sampling. The blurring in these Spiral images was minimized to a level comparable to that in gradient-echo images with rectangular acquisitions, while the Spiral acquisition efficiency was maintained at eight. These images showed that Spiral imaging at 7T was feasible. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

  • High-resolution Spiral imaging on a whole-body 7T scanner with minimized image blurring
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Yongxian Qian, Yik Kiong Hue, Tamer S. Ibrahim, Tiejun Zhao, Fernando E. Boada
    Abstract:

    High-resolution (approximately 0.22 mm) images are preferably acquired on whole-body 7T scanners to visualize minianatomic structures in human brain. They usually need long acquisition time ( approximately 12 min) in three-dimensional scans, even with both parallel imaging and partial Fourier samplings. The combined use of both fast imaging techniques, however, leads to occasionally visible undersampling artifacts. Spiral imaging has an advantage in acquisition efficiency over rectangular sampling, but its implementations are limited due to image blurring caused by a strong off-resonance effect at 7T. This study proposes a solution for minimizing image blurring while keeping Spiral efficient. Image blurring at 7T was, first, quantitatively investigated using computer simulations and point-spread functions. A combined use of multishot Spirals and ultrashort echo time acquisitions was then employed to minimize off-resonance-induced image blurring. Experiments on phantoms and healthy subjects were performed on a whole-body 7T scanner to show the performance of the proposed method. The three-dimensional brain images of human subjects were obtained at echo time = 1.18 ms, resolution = 0.22 mm (field of view = 220 mm, matrix size = 1024), and in-plane Spiral shots = 128, using a home-developed ultrashort echo time sequence (acquisition-weighted stack of Spirals). The total acquisition time for 60 partitions at pulse repetition time = 100 ms was 12.8 min without use of parallel imaging and partial Fourier sampling. The blurring in these Spiral images was minimized to a level comparable to that in gradient-echo images with rectangular acquisitions, while the Spiral acquisition efficiency was maintained at eight. These images showed that Spiral imaging at 7T was feasible.

Tiejun Zhao - One of the best experts on this subject based on the ideXlab platform.

  • high resolution Spiral imaging on a whole body 7t scanner with minimized image blurring
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Yongxian Qian, Tamer S. Ibrahim, Tiejun Zhao, Fernando E. Boada
    Abstract:

    High-resolution (∼0.22 mm) images are preferably acquired on whole-body 7T scanners to visualize minianatomic structures in human brain. They usually need long acquisition time (∼12 min) in three-dimensional scans, even with both parallel imaging and partial Fourier samplings. The combined use of both fast imaging techniques, however, leads to occasionally visible undersampling artifacts. Spiral imaging has an advantage in acquisition efficiency over rectangular sampling, but its implementations are limited due to image blurring caused by a strong off-resonance effect at 7T. This study proposes a solution for minimizing image blurring while keeping Spiral efficient. Image blurring at 7T was, first, quantitatively investigated using computer simulations and point-spread functions. A combined use of multishot Spirals and ultrashort echo time acquisitions was then employed to minimize off-resonance-induced image blurring. Experiments on phantoms and healthy subjects were performed on a whole-body 7T scanner to show the performance of the proposed method. The three-dimensional brain images of human subjects were obtained at echo time = 1.18 ms, resolution = 0.22mm (field of view = 220mm, matrix size = 1024), and in-plane Spiral shots = 128, using a home-developed ultrashort echo time sequence (acquisition-weighted stack of Spirals). The total acquisition time for 60 partitions at pulse repetition time = 100 ms was 12.8 min without use of parallel imaging and partial Fourier sampling. The blurring in these Spiral images was minimized to a level comparable to that in gradient-echo images with rectangular acquisitions, while the Spiral acquisition efficiency was maintained at eight. These images showed that Spiral imaging at 7T was feasible. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

  • High-resolution Spiral imaging on a whole-body 7T scanner with minimized image blurring
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Yongxian Qian, Yik Kiong Hue, Tamer S. Ibrahim, Tiejun Zhao, Fernando E. Boada
    Abstract:

    High-resolution (approximately 0.22 mm) images are preferably acquired on whole-body 7T scanners to visualize minianatomic structures in human brain. They usually need long acquisition time ( approximately 12 min) in three-dimensional scans, even with both parallel imaging and partial Fourier samplings. The combined use of both fast imaging techniques, however, leads to occasionally visible undersampling artifacts. Spiral imaging has an advantage in acquisition efficiency over rectangular sampling, but its implementations are limited due to image blurring caused by a strong off-resonance effect at 7T. This study proposes a solution for minimizing image blurring while keeping Spiral efficient. Image blurring at 7T was, first, quantitatively investigated using computer simulations and point-spread functions. A combined use of multishot Spirals and ultrashort echo time acquisitions was then employed to minimize off-resonance-induced image blurring. Experiments on phantoms and healthy subjects were performed on a whole-body 7T scanner to show the performance of the proposed method. The three-dimensional brain images of human subjects were obtained at echo time = 1.18 ms, resolution = 0.22 mm (field of view = 220 mm, matrix size = 1024), and in-plane Spiral shots = 128, using a home-developed ultrashort echo time sequence (acquisition-weighted stack of Spirals). The total acquisition time for 60 partitions at pulse repetition time = 100 ms was 12.8 min without use of parallel imaging and partial Fourier sampling. The blurring in these Spiral images was minimized to a level comparable to that in gradient-echo images with rectangular acquisitions, while the Spiral acquisition efficiency was maintained at eight. These images showed that Spiral imaging at 7T was feasible.