@article{KobusBitzUdenetal.2012,
  author    = {Kobus, Thiele and Bitz, Andreas and Uden, Mark J. van and Lagemaat, Miram W. and Rothgang, Eva and Orzada, Stephan and Heerschap, Arend and Scheenen, Tom W. J.},
  title     = {In vivo 31P MR spectroscopic imaging of the human prostate at 7 T: safety and feasibility},
  series = {Magnetic Resonance in Medicine},
  volume    = {68},
  journal   = {Magnetic Resonance in Medicine},
  number    = {6},
  publisher = {Wiley-Liss},
  address   = {New York},
  issn      = {1522-2594},
  doi       = {10.1002/mrm.24175},
  pages     = {1683 -- 1695},
  year      = {2012},
  abstract  = {31P 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 31P MR spectroscopic imaging with relevant spatial resolution in a clinically acceptable measurement time. To this end, a 31P endorectal coil was developed and combined with an eight-channel 1H 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 Burn:x-wiley:07403194:media:MRM24175:tex2gif-stack-1 measurements in a phantom and in vivo temperature measurements. The safety studies demonstrated that the presence of the 31P endorectal coil had no influence on the specific absorption rate levels and temperature distribution of the external eight-channel 1H 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 1H array coil was allowed. For transmitting with the 31P 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 31P 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.},
  language  = {en}
}
@article{LagemaatVosMaasetal.2014,
  author    = {Lagemaat, Miriam W. and Vos, Eline K. and Maas, Marnix C. and Bitz, Andreas and Orzada, Stephan and Uden, Mark J. van and Kobus, Thiele and Heerschap, Arend and Scheenen, Tom W. J.},
  title     = {Phosphorus magnetic resonance spectroscopic imaging at 7 T in patients with prostate cancer},
  series = {Investigative Radiology},
  volume    = {49},
  journal   = {Investigative Radiology},
  number    = {5},
  publisher = {Lippincott Williams \& Wilkins},
  address   = {Philadelphia, Pa.},
  issn      = {1536-0210},
  doi       = {10.1097/RLI.0000000000000012},
  pages     = {363 -- 372},
  year      = {2014},
  abstract  = {Objectives 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. Materials and Methods 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. Results 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. Conclusions 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.},
  language  = {en}
}
@article{LagemaatMaasVosetal.2015,
  author    = {Lagemaat, Miriam W. and Maas, Marnix C. and Vos, Eline K. and Bitz, Andreas and Orzada, Stephan and Weiland, Elisabeth and Uden, Mark J. van and Kobus, Thiele and Heerschap, Arend and Scheenen, Tom W. J.},
  title     = {(31) P MR spectroscopic imaging of the human prostate at 7 T: T1 relaxation times, Nuclear Overhauser Effect, and spectral characterization},
  series = {Magnetic Resonance in Medicine},
  volume    = {73},
  journal   = {Magnetic Resonance in Medicine},
  number    = {3},
  publisher = {Wiley},
  address   = {Weinheim},
  issn      = {1522-2594},
  doi       = {10.1002/mrm.25209},
  pages     = {909 -- 920},
  year      = {2015},
  language  = {en}
}
@article{LagemaatBreukelsVosetal.2016,
  author    = {Lagemaat, Miriam W. and Breukels, Vincent and Vos, Eline K. and B., Adam and Uden, Mark J. van and Orzada, Stephan and Bitz, Andreas and Maas, Marnix C. and Scheenen, Tom W. J.},
  title     = {¹H MR spectroscopic imaging of the prostate at 7T using spectral-spatial pulses},
  series = {Magnetic Resonance in Medicine},
  volume    = {75},
  journal   = {Magnetic Resonance in Medicine},
  number    = {3},
  publisher = {International Society for Magnetic Resonance in Medicine},
  issn      = {1522-2594},
  doi       = {10.1002/mrm.25569},
  pages     = {933 -- 945},
  year      = {2016},
  abstract  = {Purpose To assess the feasibility of prostate ¹H MR spectroscopic imaging (MRSI) using low-power spectral-spatial (SPSP) pulses at 7T, exploiting accurate spectral selection and spatial selectivity simultaneously. Methods A double spin-echo sequence was equipped with SPSP refocusing pulses with a spectral selectivity of 1 ppm. Three-dimensional prostate ¹H-MRSI at 7T was performed with the SPSP-MRSI sequence using an 8-channel transmit array coil and an endorectal receive coil in three patients with prostate cancer and in one healthy subject. No additional water or lipid suppression pulses were used. Results Prostate ¹H-MRSI could be obtained well within specific absorption rate (SAR) limits in a clinically feasible time (10 min). Next to the common citrate signals, the prostate spectra exhibited high spermine signals concealing creatine and sometimes also choline. Residual lipid signals were observed at the edges of the prostate because of limitations in spectral and spatial selectivity. Conclusion It is possible to perform prostate ¹H-MRSI at 7T with a SPSP-MRSI sequence while using separate transmit and receive coils. This low-SAR MRSI concept provides the opportunity to increase spatial resolution of MRSI within reasonable scan times.},
  language  = {en}
}