Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Quantitative evaluation of the lactate signal loss and its spatial dependence in PRESS localized H-1 NMR spectroscopy
Autore:
Jung, WI; Bunse, M; Lutz, O;
Indirizzi:
Max Grundig Clin, Hypertens & Diabet Res Unit, D-77815 Buhl, Germany Max Grundig Clin Buhl Germany D-77815 et Res Unit, D-77815 Buhl, Germany Univ Tubingen, Inst Phys, D-72076 Tubingen, Germany Univ Tubingen Tubingen Germany D-72076 t Phys, D-72076 Tubingen, Germany
Titolo Testata:
JOURNAL OF MAGNETIC RESONANCE
fascicolo: 2, volume: 152, anno: 2001,
pagine: 203 - 213
SICI:
1090-7807(200110)152:2<203:QEOTLS>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
HOMONUCLEAR SPIN SYSTEMS;
Keywords:
localized H-1 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, D-77815 Buhl, Germany Max Grundig Clin Buhl Germany D-77815 it, D-77815 Buhl, Germany
Citazione:
W.I. Jung et al., "Quantitative evaluation of the lactate signal loss and its spatial dependence in PRESS localized H-1 NMR spectroscopy", J MAGN RES, 152(2), 2001, pp. 203-213

Abstract

Localized H-1 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 multiple-quantum 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, 20-mm slices) leads to 54% signal loss from NDOS and up to 24% from PT, leading to a maximum signal loss of 78%. Using RE-BURP 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.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 05/04/20 alle ore 04:10:21