title: Introducing parametric fusion PET/MRI of primary prostate cancer.
abstract: We assessed the performance of parametric fusion PET/MRI based on (11)C-choline PET/CT and apparent diffusion coefficient (ADC) maps derived from diffusion-weighted MRI for the identification of primary prostate cancer.
  
  
  METHODS
  (11)C-choline PET/CT and MRI were performed in 17 patients with untreated primary prostate cancer, followed by prostatectomy. Registration of in vivo imaging with histology was achieved using a mutual-information objective function and by performing ex vivo MRI of the prostatectomy specimen (obtained at 3 T) and whole-mount sectioning with block-face photography as intermediate steps. Data analysis included volumetrically registered whole-mount histology with Gleason scoring, (11)C-choline, and ADC data (obtained at 1.5 T). Volumes of interest were defined on the basis of histologically proven tumor tissue to calculate tumor-to-benign prostate background ratios (TBRs) for (11)C-choline, ADC, and a derived fusion PET/MRI parameter calculating the quotient of (11)C-choline over ADC (P(CHOL/ADC)).
  
  
  RESULTS
  Fifty-one tumor nodules were identified at pathology. The TBRs for (11)C-choline (P < 0.05) and P(CHOL/ADC) (P < 0.005) were significantly higher in prostate cancers with a Gleason score of ≥3 + 4 than with a Gleason score of ≤3 + 3 disease and controls. For Gleason ≥ 3 + 4, the ADC TBRs were significantly lower than controls and Gleason ≤ 3 + 3 disease (P < 0.05). The absolute value of TBRs obtained from Gleason ≥ 3 + 4 cancers increased from ADC to (11)C-choline PET/CT and from (11)C-choline PET/CT to P(CHOL/ADC), with each step being statistically significant.
  
  
  CONCLUSIONS
  Our data indicate that parametric PET/MRI using P(CHOL/ADC) improves lesion-to-background contrast (TBRs) of Gleason ≥ 3 + 4 disease, compared with (11)C-choline PET/CT or diffusion-weighted MRI, and thus hold promise that parametric imaging performed on hybrid PET/MRI may further improve identification and localization of significant primary prostate cancer.
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Hyunjin
authors.initials: H
authors.lastname: Park
authors.forename: David
authors.initials: D
authors.lastname: Wood
authors.forename: Hero
authors.initials: H
authors.lastname: Hussain
authors.forename: Charles R
authors.initials: CR
authors.lastname: Meyer
authors.forename: Rajal B
authors.initials: RB
authors.lastname: Shah
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Johnson
authors.forename: Thomas
authors.initials: T
authors.lastname: Chenevert
authors.forename: Morand
authors.initials: M
authors.lastname: Piert
mesh_terms: D002250:Carbon Radioisotopes; D002794:Choline; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging
chemical_list: D002250:Carbon Radioisotopes; D002794:Choline