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Titolo: Quantitative evaluation of the lactate signal loss and its spatial dependence in PRESS localized H1 NMR spectroscopy
Autore: Jung, WI; Bunse, M; Lutz, O;
 Indirizzi:
 Max Grundig Clin, Hypertens & Diabet Res Unit, D77815 Buhl, Germany Max Grundig Clin Buhl Germany D77815 et Res Unit, D77815 Buhl, Germany Univ Tubingen, Inst Phys, D72076 Tubingen, Germany Univ Tubingen Tubingen Germany D72076 t Phys, D72076 Tubingen, Germany
 Titolo Testata:
 JOURNAL OF MAGNETIC RESONANCE
fascicolo: 2,
volume: 152,
anno: 2001,
pagine: 203  213
 SICI:
 10907807(200110)152:2<203:QEOTLS>2.0.ZU;2#
 Fonte:
 ISI
 Lingua:
 ENG
 Soggetto:
 HOMONUCLEAR SPIN SYSTEMS;
 Keywords:
 localized H1 NMR spectroscopy; lactate; PRESS;
 Tipo documento:
 Article
 Natura:
 Periodico
 Settore Disciplinare:
 Life Sciences
 Physical, Chemical & Earth Sciences
 Citazioni:
 13
 Recensione:
 Indirizzi per estratti:
 Indirizzo: Jung, WI Max Grundig Clin, Hypertens & Diabet Res Unit, D77815 Buhl, Germany Max Grundig Clin Buhl Germany D77815 it, D77815 Buhl, Germany



 Citazione:
 W.I. Jung et al., "Quantitative evaluation of the lactate signal loss and its spatial dependence in PRESS localized H1 NMR spectroscopy", J MAGN RES, 152(2), 2001, pp. 203213
Abstract
Localized H1 NMR spectroscopy using the 90 degrees  t(1)  180 degrees t(1) + t(2)  180 degrees  t(2)  Acq. PRESS sequence can lead to a signal loss for the lactate doublet compared with signals from uncoupled nuclei which is dependent on the choice of tl and t2. The most striking signal loss of up to 78% of the total signal occurs with the symmetrical PRESS sequence (t(1) = t(2)) at an echo time of 2/J (similar or equal to 290 ms). Calculations have shown that this signal loss is related to the pulse angle distributions produced by the two refocusing pulses which leads to the creationof single quantum polarization transfer (PT) as well as to not directly observable states (NDOS) of the lactate AX(3) spin system: zero and multiplequantum coherences, and longitudinal spin orders. In addition, the chemical shift dependent voxel displacement (VOD) leads to further signal loss. Bycalculating the density operator for various of the echo times TE = n/J, n= 1, 2, 3,..., we calculated quantitatively the contributions of these effects to the signal loss as well as their spatial distribution. A maximum signal loss of 75% can be expected from theory for the symmetrical PRESS sequence and TE = 2/J for Hamming filtered sinc pulses, whereby 47% are due to the creation of NDOS and up to 28% arise from PT, Taking also the VOD effect into account (2 mT/m slice selection gradients, 20mm slices) leads to 54% signal loss from NDOS and up to 24% from PT, leading to a maximum signal loss of 78%. Using REBURP pulses with their more rectangular pulse angle distributions reduces the maximum signal loss to 44%. Experiments at 1.5 T using a lactate solution demonstrated a maximum lactate signal loss for sincpulses of 82% (52% NDOS, 30% PT) at TE = 290 ms using the symmetrical PRESS sequence. The great signal loss and its spatial distribution is of importance for investigations using asymmetrical PRESS sequence at TE=2/J. (C) 2001 Academic Press.
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Documento generato il 05/04/20 alle ore 04:10:21