The aim of this study was to identify characteristics of phosphorus (31P) spectra of the human prostate and to investigate changes of individual phospholipid metabolites in prostate cancer through in vivo 31P magnetic resonance spectroscopic imaging (MRSI) at 7 T.
In this institutional review board–approved study, 15 patients with biopsy-proven prostate cancer underwent T2-weighted magnetic resonance imaging and 3-dimensional 31P MRSI at 7 T. Voxels were selected at the tumor location, in normal-appearing peripheral zone tissue, normal-appearing transition zone tissue, and in the base of the prostate close to the seminal vesicles. Phosphorus metabolite ratios were determined and compared between tissue types.
Signals of phosphoethanolamine (PE) and phosphocholine (PC) were present and well resolved in most 31P spectra in the prostate. Glycerophosphocholine signals were observable in 43% of the voxels in malignant tissue, but in only 10% of the voxels in normal-appearing tissue away from the seminal vesicles. In many spectra, independent of tissue type, 2 peaks resonated in the chemical shift range of inorganic phosphate, possibly representing 2 separate pH compartments. The PC/PE ratio in the seminal vesicles was highly elevated compared with the prostate in 5 patients. A considerable overlap of 31P metabolite ratios was found between prostate cancer and normal-appearing prostate tissue, preventing direct discrimination of these tissues. The only 2 patients with high Gleason scores tumors (≥4+5) presented with high PC and glycerophosphocholine levels in their cancer lesions.
Phosphorus MRSI at 7 T shows distinct features of phospholipid metabolites in the prostate gland and its surrounding structures. In this exploratory study, no differences in 31P metabolite ratios were observed between prostate cancer and normal-appearing prostate tissue possibly because of the partial volume effects of small tumor foci in large MRSI voxels.
From the *Department of Radiology, Radboud University Medical Center, Nijmegen, The Netherlands; and †Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany.
Received for publication July 15, 2013; and accepted for publication, after revision, October 5, 2013.
Conflicts of interest and sources of funding: Supported by grant number 243115 from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007–2013).
The authors declare no conflicts of interest.
Reprints: Miriam W. Lagemaat, MSc, Department of Radiology, Radboud University Medical Center, (post 767), PO Box 9101, 6500 HB Nijmegen, The Netherlands. E-mail: firstname.lastname@example.org.