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Abstract:
Purpose/Introduction:
Magnetic resonance spectroscopy (MRS) is a valu-
able tool for differential diagnostics of various neuropathologies. However, spinal cord MRS has rarely been applied in clinical work due to technical challenges, including strong susceptibility changes in the region and its finite diameter, which limit the attainable signal to noise ratio (SNR) and distort the lineshape. Hence, extensive signal averaging is required, which increases the likelihood of B 0 changes caused by patient motion (respiration, swallowng,...), cord motion, and scanner drift. To avoid incoherent signal averaging, it would be ideal to perform frequency alignment and phase correction
before averaging. Unfortunately, frequency alignment of individual FIDs is not possible due to the low SNR of the metabolite peaks.
In this work:
Non-water suppressed proton MR spectroscopy with the metabolite cycling (MC) technique 1,2,3 allows the use of the high SNR water peak of individual FIDs for frequency alignment.
Subjects and Methods:
After the approval from the local ethics committee, 13 volunteers were measured at a 3T whole body MR scanner (Achieva, Philips Medical Systems). ECG-triggered PRESS localization was used for data acquisition preceded by either the up- or down-field MC inversion pulse. Inner volume saturation (IVS) was used to minimize the chemical shift displacement between metabolites (Fig. 1).
Discussion/Conclusion:
Non-water-suppressed MRS offers the opportunity to perform frequency alignment of individual FIDs even with the very low SNR available in the spinal cord. The significantly decreased CRLB of all metabolites demonstrate that this technique improves spectral quality compared to VAPOR water suppressed spectroscopy. Future work will explore the technique in patients suffering from differentneuropathologies e.g. spinal cord tumors.
