In vivo localized 1H NMR spectroscopy: an experimental characterization of the PRESS technique

The aim of this study was the experimental characterization of the PRESS technique for image-guided in vivo 1H NMR spectroscopy, as implemented on a commercially available 1.5 T NMR whole-body system. Three characterization parameters were defined and evaluated in test object measurements: selection efficiency, suppression efficiency and contamination. The characterization parameters were evaluated in different experimental conditions. The profile of signal intensity across the volume of interest (VOI) was investigated. Our results show that the characterization parameters are slightly affected by the echo time, while they are not affected by changes in the repetition time. When the VOI is co-extensive with the inner cube of the test object the suppression efficiency is good but the selection efficiency is not very high. Contamination is affected by the synthesizer frequency offset, while the selection efficiency is quite stable. Contamination effects become significant in case of 90 degrees pulse maladjustment.