Evaluation of chemical shift imaging using a two-dimensional PRESSCS1 sequence: work in progress

Chemical shift imaging has not been widely used for clinical studies due to technical difficulties and current imaging quality. The purpose of this study was to find solutions to improve quality of chemical shift imaging. Both phantom and patient studies were carried out in this study. Eleven clinical patients were scanned with 2-dimensional chemical shift imaging (2D CSI) sequence. The study was performed on two 1.5-T GE Signa scanners. The 2D CSI scans were acquired using a point resolved spectroscopy (PRESS) CSI sequence. The acquisition matrix was 18×18 phase encodings over a 24-cm FOV. The slice thickness was 10 mm. TR was 1000 msec and TE was 144 msec. One excitation was acquired which gave an acquisition time of 5:28. Two SCI scans were performed with outer-volume saturation bands and without outer- volume saturation bands. Spectroscopy data were processed using GE Functool software. Without outer-volume saturation bands, the maps of metabolites were in a poor quality, generally showing higher concentration of metabolite in the center of volume of interest. With outer volume saturation, 2D CSI scans were successfully performed. Improved maps of metabolites were obtained with outer-volume saturation bands in both phantom and patient studies. Compared with the scans obtained without outer-volume bands, peripheral signal loss was reduced with outer-volume saturation bands. Outer volume saturation bands can be used to reduce fat contamination, and contaminations from air, water, other substances as well. Outer-volume saturation bands improve quality of chemical shift imaging.