Grzegorz L Chadzynski1, Uwe Klose. 1. MR Research Group, Department of Diagnostic and Interventional Neuroradiology, University Hospital Tuebingen, Hoppe-Seyler Strasse 3, 72076, Tuebingen, Germany. grzegorz.chadzynski@med.uni-tuebingen.de
Abstract
OBJECT: Non-water-suppressed MRSI (magnetic resonance spectroscopy imaging) offers a number of advantages; however, spectra are hampered by the sideband artifacts. The origin of those is associated with the vibration of the gradient coils, and most of the sidebands are assumed to be related to the crusher gradients. The aim was to examine the dependency between the physical direction of the crushers and the sidebands. Additionally, the possibilities of optimization of the point resolved spectroscopy sequence (PRESS) were investigated. MATERIALS AND METHODS: For the assessment of the sidebands, spectra at short echo time (TE) were collected at 3 T from standard water phantom. A homemade agar phantom was used to test the optimal strength of the crusher gradients. Optimized PRESS sequence was tested in vivo. RESULTS: The greatest sidebands were found to be associated with the crusher gradient in x-direction. Agar phantom and in vivo measurements revealed that reduction of the crusher's strength to 5 mT/m could provide a significant minimization of the sidebands without raising the unwanted signals produced by volume selection. CONCLUSION: This study demonstrates that crusher gradients in different directions produce a unique pattern of the sidebands. Moreover, optimization of the strength of crushers has been found to decrease sidebands so, the remaining part could be reduced in postprocessing.
OBJECT: Non-water-suppressed MRSI (magnetic resonance spectroscopy imaging) offers a number of advantages; however, spectra are hampered by the sideband artifacts. The origin of those is associated with the vibration of the gradient coils, and most of the sidebands are assumed to be related to the crusher gradients. The aim was to examine the dependency between the physical direction of the crushers and the sidebands. Additionally, the possibilities of optimization of the point resolved spectroscopy sequence (PRESS) were investigated. MATERIALS AND METHODS: For the assessment of the sidebands, spectra at short echo time (TE) were collected at 3 T from standard water phantom. A homemade agar phantom was used to test the optimal strength of the crusher gradients. Optimized PRESS sequence was tested in vivo. RESULTS: The greatest sidebands were found to be associated with the crusher gradient in x-direction. Agar phantom and in vivo measurements revealed that reduction of the crusher's strength to 5 mT/m could provide a significant minimization of the sidebands without raising the unwanted signals produced by volume selection. CONCLUSION: This study demonstrates that crusher gradients in different directions produce a unique pattern of the sidebands. Moreover, optimization of the strength of crushers has been found to decrease sidebands so, the remaining part could be reduced in postprocessing.
Authors: Erin L MacMillan; Daniel G Q Chong; Wolfgang Dreher; Anke Henning; Chris Boesch; Roland Kreis Journal: Magn Reson Med Date: 2011-03-10 Impact factor: 4.668