Short echo time proton MR spectroscopic imaging.
Proton spectroscopic imaging at short TEs (20-30 ms) in human brain requires volume preselection inside the brain to suppress overwhelming lipid and water signals from surrounding tissue. In this article we discuss limitations of conventional volume preselection using stimulated echoes that lead to spectral contamination from surrounding tissue. Improved volume preselection was obtained by adding a complete outer volume suppression (presaturation). The performance of the method is illustrated on normal volunteers and on clinical cases with brain tumors and multiple sclerosis (MS) plaques. In normal human brain, we detected resonances with short T2 values and complex J-coupling, including rather broad methyl/methylene resonances in the chemical shift range between 0 and 2 ppm. Spectroscopic images obtained on patients with intracranial tumors and on one patient with several MS plaques demonstrate the possibility of detecting regional distributions of increased methyl/methylene resonances between 0 and 2 ppm in brain lesions.