title: Optimization of Acquisition time of 68Ga-PSMA-Ligand PET/MRI in Patients with Local and Metastatic Prostate Cancer.
abstract: OBJECTIVE
  The aim of this optimization study was to minimize the acquisition time of 68Ga-HBED-CC-PSMA positron emission tomography/magnetic resonance imaging (PET/MRI) in patients with local and metastatic prostate cancer (PCa) to obtain a sufficient image quality and quantification accuracy without any appreciable loss.
  
  
  METHODS
  Twenty patients with PCa were administered intravenously with the 68Ga-HBED-CC-PSMA ligand (mean activity 99 MBq/patient, range 76-148 MBq) and subsequently underwent PET/MRI at, on average, 168 min (range 77-320 min) after injection. PET and MR imaging data were acquired simultaneously. PET acquisition was performed in list mode and PET images were reconstructed at different time intervals (1, 2, 4, 6, 8, and 10 min). Data were analyzed regarding radiotracer uptake in tumors and muscle tissue and PET image quality. Tumor uptake was quantified in terms of the maximum and mean standardized uptake value (SUVmax, SUVmean) within a spherical volume of interest (VOI). Reference VOIs were drawn in the gluteus maximus muscle on the right side. PET image quality was evaluated by experienced nuclear physicians/radiologists using a five-point ordinal scale from 5-1 (excellent-insufficient).
  
  
  RESULTS
  Lesion detectability linearly increased with increasing acquisition times, reaching its maximum at PET acquisition times of 4 min. At this image acquisition time, tumor lesions in 19/20 (95%) patients were detected. PET image quality showed a positive correlation with increasing acquisition time, reaching a plateau at 4-6 min image acquisition. Both SUVmax and SUVmean correlated inversely with acquisition time and reached a plateau at acquisition times after 4 min.
  
  
  CONCLUSIONS
  In the applied image acquisition settings, the optimal acquisition time of 68Ga-PSMA-ligand PET/MRI in patients with local and metastatic PCa was identified to be 4 min per bed position. At this acquisition time, PET image quality and lesion detectability reach a maximum while SUVmax and SUVmean do not change significantly beyond this time point.
authors.affiliation: Clinic for Nuclear Medicine, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Lütje
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Blex
authors.affiliation: Clinic for Nuclear Medicine, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Gomez
authors.affiliation: University Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, Moorenstraße 5, 40225 Dusseldorf, Germany.
authors.forename: Benedikt M
authors.initials: BM
authors.lastname: Schaarschmidt
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany.
authors.forename: Lale
authors.initials: L
authors.lastname: Umutlu
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Forsting
authors.affiliation: Clinic for Nuclear Medicine, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Jentzen
authors.affiliation: Clinic for Nuclear Medicine, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bockisch
authors.affiliation: Clinic for Nuclear Medicine, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany.
authors.forename: Thorsten D
authors.initials: TD
authors.lastname: Poeppel
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Wetter
mesh_terms: D061605:Administration, Intravenous; D000368:Aged; D000369:Aged, 80 and over; D004492:Edetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D049268:Positron-Emission Tomography; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D019275:Radiopharmaceuticals / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors
chemical_list: D019275:Radiopharmaceuticals; C075313:N,N'-bis(2-hydroxy-5-(ethylene-beta-carboxy)benzyl)ethylenediamine N,N'-diacetic acid; D004492:Edetic Acid