In Vivo (31) P MR spectroscopic imaging of the human prostate at 7 T: Safety and feasibility - Abstract

31 P MR spectroscopic imaging of the human prostate provides information about phosphorylated metabolites that could be used for prostate cancer characterization.

The sensitivity of a magnetic field strength of 7 T might enable 3D 31 P MR spectroscopic imaging with relevant spatial resolution in a clinically acceptable measurement time. To this end, a 31 P endorectal coil was developed and combined with an eight-channel 1 H body-array coil to relate metabolic information to anatomical location. An extensive safety validation was performed to evaluate the specific absorption rate, the radiofrequency field distribution, and the temperature distribution of both coils. This validation consisted of detailed Finite Integration Technique simulations, confirmed by MR thermometry and B 1+ measurements in a phantom and in vivo temperature measurements. The safety studies demonstrated that the presence of the 31 P endorectal coil had no influence on the specific absorption rate levels and temperature distribution of the external eight-channel 1 H array coil. To stay within a 10 g averaged local specific absorption rate of 10 W/kg, a maximum time-averaged input power of 33 W for the 1 H array coil was allowed. For transmitting with the 31 P endorectal coil, our safety limit of less than 1°C temperature increase in vivo during a 15-min MR spectroscopic imaging experiment was reached at a time-averaged input power of 1.9 W. With this power setting, a second in vivo measurement was performed on a healthy volunteer. Using adiabatic excitation, 3D 31 P MR spectroscopic imaging produced spectra from the entire prostate in 18 min with a spatial resolution of 4 cm3 . The spectral resolution enabled the separate detection of phosphocholine, phosphoethanolamine, inorganic phosphate, and other metabolites that could play an important role in the characterization of prostate cancer.

Written by: 
Kobus T, Bitz AK, van Uden MJ, Lagemaat MW, Rothgang E, Orzada S, Heerschap A, Scheenen TW. Are you the author? 
Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.

Reference: Magn Reson Med. 2012 Feb 24. Epub ahead of print. 
doi: 10.1002/mrm.24175 

PubMed Abstract 
PMID: 22368094