In Vivo ³¹P-MRS of the Human Orthotopic Kidney at 3 Tesla

Phosphorus magnetic resonance spectroscopy (³¹P-MRS) is a noninvasive in vivo tool for identification and quantification of phosphorus-containing metabolites involved in cell membrane synthesis and degradation, as well as in the energy-producing pathways essential for cell functions. However, the considerable depth of the orthotopic kidneys in the human body, combined with the inherently low sensitivity of ³¹P-MRS, makes measurement of the spectra particularly challenging. Despite these difficulties, the acquisition of phosphorus spectra from normal orthotopic kidney is important for studies of kidney physiology and disease, as well as for evaluation of human allograft viability and function before and after renal transplantation. The aim of the present study was to investigate whether ³¹P spectra of orthotopic kidneys can be acquired with improved spectral quality within a clinically acceptable acquisition time using a contemporary 3T MR scanner. Spectra from healthy volunteers were obtained using a single-voxel image-selected in vivo spectroscopy (ISIS) sequence, combined with proton (¹H) decoupling and nuclear Overhauser effect enhancement. We demonstrate that ³¹P spectra with improved spectral resolution and signal-to-noise ratio can be acquired on a clinical 3T scanner within an acceptable acquisition time. However, careful selection of the volume of interest is essential, taking into account the transmitter excitation profile and the chemical shift displacement of the voxels corresponding to different spectral components. The reference phosphorus spectra of healthy orthotopic kidney may serve as a valuable baseline for assessing alterations and changes in renal metabolism associated with disease and transplantation.