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ABSTRACT: Magnetic resonance imaging has rarely been applied to rigid polymeric materials, due primarily to the strong dipolar coupling
and short signal lifetimes inherent in these materials. SPRITE (single point ramped imaging withT
1 enhancement) (B. J. Balcom, R. P. MacGregor, S. D. Beyea, D. P. Green, R. L. Armstrong, T. W. Bremner: J. Magn. Reson. A123, 131–134, 1996) is particularly well suited to imaging solid materials. With SPRITE, the only requirement is thatT
2* be long enough so that the signal can be phase-encoded. The minimum phase encoding time is limited by the maximum gradient
strength available and by the instrument deadtime. At present this is usually tens of microseconds and will only improve with
refinements in technology. We have used the SPRITE sequence in conjunction with raising the sample temperature to obtain images
of rigid polymers that have largely frustrated conventional imaging methods. This approach provides a straightforward and
reliable method for imaging a class of samples that, up until now, have been very difficult to image.
Applied Magnetic Resonance 04/2012; 22(2):247-256. · 0.75 Impact Factor
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ACM Trans. Math. Softw. 01/2007; 33.
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ABSTRACT: Sodium density maps acquired with three SPRITE-based methods have been compared in terms of the resulting quantitative information as well as image quality and acquisition times. Consideration of factors relevant for the clinical implementation of SPRITE shows that the Conical-SPRITE variant is preferred because of a 20-fold reduction in acquisition time, slightly improved image quality, and no loss of quantitative information. The acquisition of a 3D data set (32x32x16; FOV=256x256x160 mm) for the quantitative determination of sodium density is demonstrated. In vivo Conical-SPRITE 23Na images of the brain of a healthy volunteer were acquired in 30 min with a resolution of 7.5x7.5x7.5 mm and a signal-to-noise ratio of 23 in cerebrospinal fluid and 17 in brain tissue.
Journal of Magnetic Resonance 04/2006; 179(1):64-72. · 2.14 Impact Factor
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ABSTRACT: A version of the chirp z-transform (CZT) enabling signal intensity and phase-preserving field-of-view scaling has been programmed. The algorithm is important for all single-point imaging sequences such as SPRITE when used with multiple data acquisition for T2* mapping or signal averaging. CZT has particular utility for SPRITE imaging of nuclei with short relaxation times such as sodium at high field. Here, a complete theory of the properties of CZT is given. This method operates entirely in k-space. It is compared with a conventional interpolation approach that works in image space after the application of a fast Fourier transformation.
Journal of Magnetic Resonance 02/2006; 178(1):121-8. · 2.14 Impact Factor
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ABSTRACT: Two strategies for the optimization of centric scan SPRITE (single point ramped imaging with T1 enhancement) magnetic resonance imaging techniques are presented. Point spread functions (PSF) for the centric scan SPRITE methodologies are numerically simulated, and the blurring manifested in a centric scan SPRITE image through PSF convolution is characterized. Optimal choices of imaging parameters and k-space sampling scheme are predicted to obtain maximum signal-to-noise ratio (SNR) while maintaining acceptable image resolution. The point spread function simulation predictions are verified experimentally. The acquisition of multiple FID points following each RF excitation is described and the use of the Chirp z-Transform algorithm for the scaling of field of view (FOV) of the reconstructed images is illustrated. Effective recombination of the rescaled images for SNR improvement and T*2 mapping is demonstrated.
Journal of Magnetic Resonance 08/2004; 169(1):102-17. · 2.14 Impact Factor
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ABSTRACT: Two strategies for the optimization of centric scan SPRITE (single point ramped imaging with T1 enhancement) magnetic resonance imaging techniques are presented. Point spread functions (PSF) for the centric scan SPRITE methodologies are numerically simulated, and the blurring manifested in a centric scan SPRITE image through PSF convolution is characterized. Optimal choices of imaging parameters and k-space sampling scheme are predicted to obtain maximum signal-to-noise ratio (SNR) while maintaining acceptable image resolution. The point spread function simulation predictions are verified experimentally. The acquisition of multiple FID points following each RF excitation is described and the use of the Chirp z-Transform algorithm for the scaling of field of view (FOV) of the reconstructed images is illustrated. Effective recombination of the rescaled images for SNR improvement and T2* mapping is demonstrated.
Journal of Magnetic Resonance.
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[show abstract]
[hide abstract]
ABSTRACT: Sodium density maps acquired with three SPRITE-based methods have been compared in terms of the resulting quantitative information as well as image quality and acquisition times. Consideration of factors relevant for the clinical implementation of SPRITE shows that the Conical-SPRITE variant is preferred because of a 20-fold reduction in acquisition time, slightly improved image quality, and no loss of quantitative information. The acquisition of a 3D data set (32 × 32 × 16; FOV = 256 × 256 × 160 mm) for the quantitative determination of sodium density is demonstrated. In vivo Conical-SPRITE 23Na images of the brain of a healthy volunteer were acquired in 30 min with a resolution of 7.5 × 7.5 × 7.5 mm and a signal-to-noise ratio of 23 in cerebrospinal fluid and 17 in brain tissue.
Journal of Magnetic Resonance.
