title: Multiple Time-Point 68Ga-PSMA I&T PET/CT for Characterization of Primary Prostate Cancer: Value of Early Dynamic and Delayed Imaging.
abstract: OBJECTIVE
  The aims of this study were to gain mechanistic insights into prostate cancer biology using dynamic imaging and to evaluate the usefulness of multiple time-point Ga-prostate-specific membrane antigen (PSMA) I&T PET/CT for the assessment of primary prostate cancer before prostatectomy.
  
  
  METHODS
  Twenty patients with prostate cancer underwent Ga-PSMA I&T PET/CT before prostatectomy. The PET protocol consisted of early dynamic pelvic imaging, followed by static scans at 60 and 180 minutes postinjection (p.i.). SUVs, time-activity curves, quantitative analysis based on a 2-tissue compartment model, Patlak analysis, histopathology, and Gleason grading were compared between prostate cancer and benign prostate gland.
  
  
  RESULTS
  Primary tumors were identified on both early dynamic and delayed imaging in 95% of patients. Tracer uptake was significantly higher in prostate cancer compared with benign prostate tissue at any time point (P ≤ 0.0003) and increased over time. Consequently, the tumor-to-nontumor ratio within the prostate gland improved over time (2.8 at 10 minutes vs 17.1 at 180 minutes p.i.). Tracer uptake at both 60 and 180 minutes p.i. was significantly higher in patients with higher Gleason scores (P < 0.01). The influx rate (Ki) was higher in prostate cancer than in reference prostate gland (0.055 [r = 0.998] vs 0.017 [r = 0.996]).
  
  
  CONCLUSIONS
  Primary prostate cancer is readily identified on early dynamic and static delayed Ga-PSMA ligand PET images. The tumor-to-nontumor ratio in the prostate gland improves over time, supporting a role of delayed imaging for optimal visualization of prostate cancer.
authors.affiliation: From the Departments of *Nuclear Medicine, †Medical Physics and Radiation Protection, ‡Urology and Urological Oncology, and §Radiation and Special Oncology, Hannover Medical School, Hannover; and ∥Department of Pharmaceutical Radiochemistry, Technical University Munich, Munich, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schmuck
authors.forename: Martin
authors.initials: M
authors.lastname: Mamach
authors.forename: Florian
authors.initials: F
authors.lastname: Wilke
authors.forename: Christoph A
authors.initials: CA
authors.lastname: von Klot
authors.forename: Christoph
authors.initials: C
authors.lastname: Henkenberens
authors.forename: James T
authors.initials: JT
authors.lastname: Thackeray
authors.forename: Jan M
authors.initials: JM
authors.lastname: Sohns
authors.forename: Lilli
authors.initials: L
authors.lastname: Geworski
authors.forename: Tobias L
authors.initials: TL
authors.lastname: Ross
authors.forename: Hans-Juergen
authors.initials: HJ
authors.lastname: Wester
authors.forename: Hans
authors.initials: H
authors.lastname: Christiansen
authors.forename: Frank M
authors.initials: FM
authors.lastname: Bengel
authors.forename: Thorsten
authors.initials: T
authors.lastname: Derlin
mesh_terms: D000368:Aged; D004492:Edetic Acid / Q000031:analogs & derivatives*; D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D006801:Humans; D008024:Ligands; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009842:Oligopeptides; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D011467:Prostate / Q000000981:diagnostic imaging / Q000601:surgery; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D013997:Time Factors
chemical_list: D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D008024:Ligands; D009842:Oligopeptides; C000718244:gallium 68 PSMA-11; D004492:Edetic Acid