3D 31P spectroscopic imaging of the human heart at 4.1 T.

High field (4 Tesla) spectroscopic imaging offers the advantages of increased signal-to-noise ratio and the possibility of acquiring high resolution metabolite images. We have applied a three dimensional spectroscopic imaging sequence using a sparse Gaussian sampling method to acquire phosphocreatine (PCr) images of the human heart with 8-cc voxels. PCr images enabled observation of the septum, left ventricular free wall, apex, and skeletal muscle. Quantitative evaluation of the 50 myocardial voxels acquired from 10 studies of healthy adults revealed a PCr/adenosine triphosphate (ATP) ratio of 1.80 +/- 0.32 after correction for saturation effects. Due to the small size of the voxels and the ability to choose the location of the volumes to minimize inclusion of blood, no correction for blood pool ATP was required. The calculated PCr/ATP ratio is in agreement with other studies at 1.5 and 4.0 T.

Spectroscopy and imaging with a 4 tesla whole-body MR system.

Magnetic resonance (MR) spectroscopy and imaging experiments on humans were performed with a whole-body MR system at a static field of 4 tesla. Spectroscopic studies focussed on 1H, 13C, and 31P. Imaging of humans turned out to be possible, although below the optimum at this field. This holds especially for body imaging, since RF penetration effects and dielectric resonances influence the RF field homogeneity. Excellent volume selective proton spectra of the human cerebrum and cerebellum were obtained using the stimulated echo method. Natural abundance carbon spectra of the human calf were acquired both undecoupled and with narrowband decoupling, resolving the various triglyceride resonances. Broadband decoupling, however, would have violated SAR guidelines. Liver glycogen was detected on natural abundance 13C spectra.