title: Optimizing an 18F-NaF and 18F-FDG cocktail for PET assessment of metastatic castration-resistant prostate cancer.
abstract: BACKGROUND
  PET/computed tomography (CT) imaging with the sodium-(F)-fluoride/2-(F)-fluoro-2-deoxy-D-glucose (F-NaF/F-FDG) cocktail has been proposed for patients with osseous metastases. This work aimed to optimize the cocktail composition for patients with metastatic castration-resistant prostate cancer (mCRPC).
  
  
  METHODS
  The study was carried out on six patients with mCRPC, with a total of 26 analyzed lesions. The patients were injected with F-NaF and F-FDG at separate time points. Dynamic PET/CT imaging recorded the uptake time course for both the tracers into osseous metastases. F-NaF and F-FDG uptakes were decoupled by kinetic analysis, which enabled calculation of F-NaF and F-FDG standardized uptake values (SUVs) images. Peak, mean, and total SUVs were evaluated for both tracers and all visible lesions. The F-NaF/F-FDG cocktail was optimized under the assumption that the contribution of both tracers to image formation is equal. SUV images from PET/CT imaging with a combination of F-NaF and F-FDG were generated for cocktail compositions with an F-NaF : F-FDG ratio varying from 1 : 8 to 1 : 2.
  
  
  RESULTS
  The F-NaF peak and mean SUVs were on average four to five times higher than the F-FDG peak and mean SUVs, with an interlesion coefficient of variations of 20%. The total SUV for F-NaF was on average seven times higher than that for F-FDG. When the F-NaF : F-FDG ratio changed from 1 : 8 to 1 : 2, the typical SUV on the generated PET images increased by 50%, whereas the change in the uptake visual pattern was hardly noticeable.
  
  
  CONCLUSIONS
  F-NaF and F-FDG in the cocktail contribute equally to image formation when the F-NaF : F-FDG ratio is 1 : 5. Therefore, we propose this ratio as the optimal cocktail composition for mCRPC patients. We also urge to strictly control the cocktail composition during any F-NaF/F-FDG cocktail PET/CT examination.
authors.affiliation: aJozef Stefan Institute, Ljubljana, Slovenia Departments of bMedical Physics cRadiology dGenitourinary Oncology Research Program eUniversity of Wisconsin Carbone Cancer Center, University of Wisconsin - Madison, Madison, Wisconsin, USA.
authors.forename: Urban
authors.initials: U
authors.lastname: Simoncic
authors.forename: Scott
authors.initials: S
authors.lastname: Perlman
authors.forename: Glenn
authors.initials: G
authors.lastname: Liu
authors.forename: Robert
authors.initials: R
authors.lastname: Jeraj
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography / Q000379:methods*; D064129:Prostatic Neoplasms, Castration-Resistant / Q000000981:diagnostic imaging* / Q000473:pathology*; D012969:Sodium Fluoride; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18; D012969:Sodium Fluoride