QUANTIFICATION OF SIGNAL SELECTION EFFICIENCY, EXTRA VOLUME SUPPRESSION AND CONTAMINATION FOR ISIS, STEAM AND PRESS LOCALIZED H-1-NMR SPECTROSCOPY USING AN EEC LOCALIZATION TEST OBJECT

The three most widely used single-volume NMR localization techniques ( ISIS, STEAM and PRESS) are assessed quantitatively for H-1 spectroscop y using an EEC localization test object. Signal selection efficiency, suppression of outer volume signals and contamination are measured on a 1.5 T whole-body Siemens GBS1 system. The ISIS signal selection effi ciency (volume of interest (VOI), 1-125 cm(3)) ranged from 90% to 95%, with T-1 relaxation during the sequence shown to account for the obse rved 5-10% signal loss. Contamination for ISIS was found to be higher for smaller VOIS and ranged from similar to 45% (VOI = 1 cm(3)) to sim ilar to 9% (VOI = 125 cm(3)). For PRESS, contamination ranged from 7% to 12% and it was between 3% and 8% for STEAM. However, the maximum si gnal selection efficiency for the latter two techniques (echo time, 27 0 ms) was relatively low (10-17%), and limited by T-2 losses and the n on-rectangular slice profiles of sine pulses.