Full Paper

2D arbitrary shape-selective excitation summed spectroscopy (ASSESS)

  1. Qin Qin1,2,4,*,
  2. John C. Gore3,4,
  3. Mark D. Does3,4,
  4. Malcolm J. Avison4,
  5. Robin A. de Graaf1,2

Article first published online: 20 JUL 2007

DOI: 10.1002/mrm.21274

Issue

Magnetic Resonance in Medicine

Magnetic Resonance in Medicine

Volume 58, Issue 1, pages 19–26, July 2007

Additional Information

How to Cite

Qin, Q., Gore, J. C., Does, M. D., Avison, M. J. and de Graaf, R. A. (2007), 2D arbitrary shape-selective excitation summed spectroscopy (ASSESS). Magnetic Resonance in Medicine, 58: 19–26. doi: 10.1002/mrm.21274

Author Information

  1. 1

    Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA

  2. 2

    Magnetic Resonance Research Center, Yale University, New Haven, Connecticut, USA

  3. 3

    Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA

  4. 4

    Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA

*MRRC, Yale University, TAC Building, 300 Cedar Street, P.O. Box 208043, New Haven, CT 06520-8043

Publication History

  1. Issue published online: 20 JUL 2007
  2. Article first published online: 20 JUL 2007
  3. Manuscript Accepted: 27 MAR 2007
  4. Manuscript Revised: 21 FEB 2007
  5. Manuscript Received: 3 OCT 2006

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Keywords:

  • in vivo MRS;
  • arbitrary shape localization;
  • radial trajectory in k-space;
  • bandwidth broadening;
  • concatenation

Abstract

Conventional single-voxel localization for MR spectroscopy (MRS) is restricted to selecting only rectangular-shaped regions of interest (ROIs). The complexity of tissue shapes of interest and the desire to maximize the signal-to-noise ratio (SNR) while minimizing partial-volume effects require more sophisticated localization techniques. A group of spatially selective RF pulses are proposed in this work for the measurement of spectra from regions of arbitrary shape based on using a radial trajectory in k-space. Utilizing a single k-line per excitation results in a broad spectroscopic bandwidth. However, spatial localization accuracy is compromised for nutation angles > 10° because of the small-tip-angle approximation of the Bloch equations. By interleaving multiple radial k-lines per excitation with nonselective refocusing pulses, one can achieve accurate localization for nutation angles up to 90° while simultaneously maintaining the spectral bandwidth. The technique is described and compared with existing localization methods, and in vivo results are demonstrated. Magn Reson Med 58:19–26, 2007. © 2007 Wiley-Liss, Inc.

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