title: Early dynamic imaging in68Ga- PSMA-11 PET/CT allows discrimination of urinary bladder activity and prostate cancer lesions.
abstract: OBJECTIVE
  PET/CT with68Ga-labelled prostate-specific membrane antigen (PSMA)-ligands has been proven to establish a promising imaging modality in the work-up of prostate cancer (PC) patients with biochemical relapse. Despite a high overall detection rate, the visualisation of local recurrence may be hampered by high physiologic tracer accumulation in the urinary bladder on whole body imaging, usually starting 60 min after injection. This study sought to verify whether early dynamic68Ga-PSMA-11 (HBED-CC)PET/CT can differentiate pathologic PC-related tracer uptake from physiologic tracer accumulation in the urinary bladder.
  
  
  METHODS
  Eighty consecutive PC patients referred to68Ga -PSMA-11 PET/CT were included in this retrospective analysis (biochemical relapse: n = 64; primary staging: n = 8; evaluation of therapy response/restaging: n = 8). In addition to whole-body PET/CT acquisition 60 min post injection early dynamic imaging of the pelvis in the first 8 min after tracer injection was performed. SUVmaxof pathologic lesions was calculated and time-activity curves were generated and compared to those of urinary bladder and areas of physiologic tracer uptake.
  
  
  RESULTS
  A total of 55 lesions consistent with malignancy on 60 min whole body imaging exhibited also pathologic68Ga-PSMA-11 uptake during early dynamic imaging (prostatic bed/prostate gland: n = 27; lymph nodes: n = 12; bone: n = 16). All pathologic lesions showed tracer uptake within the first 3 min, whereas urinary bladder activity was absent within the first 3 min of dynamic imaging in all patients. Suvmaxwas significantly higher in PC lesions in the first 6 min compared to urinary bladder accumulation (p < 0.001). In the subgroup of PC patients with biochemical relapse the detection rate of local recurrence could be increased from 20.3 to 29.7%.
  
  
  CONCLUSIONS
  Early dynamic imaging in68Ga-PSMA-11 PET/CT reliably enables the differentiation of pathologic tracer uptake in PC lesions from physiologic bladder accumulation. Performance of early dynamic imaging in addition to whole body imaging 60 min after tracer injection might improve the detection rate of local recurrence in PC patients with biochemical relapse referred for68Ga-PSMA-11 PET/CT.
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria. christian.uprimny@tirol-kliniken.at.
authors.forename: Christian
authors.identifier: http://orcid.org/0000-0001-5588-3363
authors.initials: C
authors.lastname: Uprimny
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria.
authors.forename: Alexander Stephan
authors.initials: AS
authors.lastname: Kroiss
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria.
authors.forename: Clemens
authors.initials: C
authors.lastname: Decristoforo
authors.affiliation: Department for Medical Statistics, Informatics and Health Economics, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Josef
authors.initials: J
authors.lastname: Fritz
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria.
authors.forename: Boris
authors.initials: B
authors.lastname: Warwitz
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Scarpa
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria.
authors.forename: Llanos Geraldo
authors.initials: LG
authors.lastname: Roig
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria.
authors.forename: Dorota
authors.initials: D
authors.lastname: Kendler
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: von Guggenberg
authors.affiliation: Department of Urology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Bektic
authors.affiliation: Department of Urology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Horninger
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria.
authors.forename: Irene Johanna
authors.initials: IJ
authors.lastname: Virgolini
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D004492:Edetic Acid / Q000031:analogs & derivatives; D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D009842:Oligopeptides; D009942:Organometallic Compounds / Q000378:metabolism; D000072078:Positron Emission Tomography Computed Tomography; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D012189:Retrospective Studies; D013997:Time Factors; D001743:Urinary Bladder / Q000000981:diagnostic imaging* / Q000378:metabolism
chemical_list: D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D009842:Oligopeptides; D009942:Organometallic Compounds; C000718244:gallium 68 PSMA-11; D004492:Edetic Acid
keywords: 68Ga-PSMA-11 PET/CT; Biochemical recurrence; Early dynamic imaging; Prostate cancer