Some comments on frequency selective excitation in newly proposed MRSI sequences

0205700 - UPT-D 20030083 RIV CZ eng C - Conference Paper (international conference)
Starčuk jr., Zenon - Horký, Jaroslav - Starčuk, Zenon - Mlynárik, V. - Gruber, S. - Moser, E.
Some comments on frequency selective excitation in newly proposed MRSI sequences.
Proceedings of 18^th conference on NMR in Valtice. Valtice: Masarykova Univerzita, 2003, s. 42. ISBN 80-210-3092-5.
[NMR Valtice. Valtice (CZ), 28.04.2002-30.04.2002]
R&D Projects: GA ČR GA202/02/1493
Institutional research plan: CEZ:AV0Z2065902
Keywords : MR spectroscopy imaging * human brain * metabolic information
Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

In many pathologies it is desirable to compare the metabolism inside a lesion, near the lesion, and in healthy tissue. The diagnostic value of MRS is enhanced by spectroscopic imaging (MRSI), permitting the simultaneous acquisition of spatially resolved spectra. In this way, assessing metabolic information about different brain regions within a single examination is possible. As with all in vivo spectroscopy, low signal-to-noise ratio (SNR) is the fundamental limiting factor in MRSI due to very low concentrations of metabolites of interest. Proton spectroscopic imaging, however, offers additional technical challenges as compared to single-voxel techniques, especially if acquisition of short echo time (TE<30 ms) is required. Critical to the success of proton MRSI studies of the human brain is the elimination of the very intense water and lipid signals arising from outside the volume of interest (VOI). Water suppression in MRSI can be very problematic in MRSI, in which the achievable degree of water suppression is limited by B₀ and B₁ inhomogeneities and water T₁ variations, invariably present throughout the larger VOIs. Suppression of liquid signals (from bone marrow and subcutaneous fat) is often severely complicated due to the fact that their relaxation behavior differs substantially from that of water. One of the basic approaches used to reduce the undesired contamination if the MRSI signals of interest consists in the use of the STEAM or PRESS selective excitation of the VOI. Both STEAM and PRESS techniques suffer from some drawbacks. STEAM reduces the sensitivity of measurement, PRESS has higher RF power requirements.
Permanent Link: http://hdl.handle.net/11104/0101313