title: In vivo (1) H MR spectroscopic imaging of aggressive prostate cancer: can we detect lactate?
abstract: OBJECTIVE
  A semi-LASER sequence was optimized for in vivo lactate detection in the prostate.
  
  
  METHODS
  The ethical committee waived the need for informed consent to measure 17 patients with high grade prostate cancer on a 3T system. A semi-LASER sequence was used with an echo time of 144 ms and optimized interpulse timing for a spectral citrate shape with high signal intensity. An LCModel basis set was developed for fitting choline, creatine, spermine, citrate, and lactate and was used to fit all spectra in tumor-containing voxels. For patients without detectable lactate, the minimal detectable lactate concentration was determined by adding in all spectra of tumor tissue a simulated lactate signal. The amplitude of the simulated lactate signal was iteratively decreased until its fit reached a Cramér Rao lower bound >20%, which was then set as the patient-specific detection limit.
  
  
  RESULTS
  In none of the patients a convincing lactate signal was found. We estimated that on average the lactate levels in high grade prostate cancer are below 1.5 mM (range 0.9-3.5 mM), Interestingly, in one patient with extensive necrosis in the tumor biopsy samples (Gleason score 5+5), large lipid resonances were observed, which originated from the tumor.
  
  
  CONCLUSIONS
  The minimal detectable lactate concentration of 1.5 mM in high grade prostate cancer indicates that if lactate is increased it remains at low concentrations.
authors.affiliation: Radiology Department, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Thiele
authors.initials: T
authors.lastname: Kobus
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Wright
authors.forename: Jack J A
authors.initials: JJ
authors.lastname: Van Asten
authors.forename: Arend
authors.initials: A
authors.lastname: Heerschap
authors.forename: Tom W J
authors.initials: TW
authors.lastname: Scheenen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D014408:Biomarkers, Tumor / Q000378:metabolism*; D003198:Computer Simulation; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008954:Models, Biological; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor; D011522:Protons; D019344:Lactic Acid
keywords: 1H MRSI; lactate; prostate cancer; semi-LASER