title: Evaluation of feasibility and image quality of 68Ga-DOTATOC positron emission tomography/magnetic resonance in comparison with positron emission tomography/computed tomography in patients with neuroendocrine tumors.
abstract: OBJECTIVE
  The primary aims of this study were to evaluate the feasibility of simultaneous 68(DOTA(0)-Phe(1)-Tyr(3))octreotide positron emission tomography (PET)/magnetic resonance (MR) acquisition on a fully integrated PET/MR scanner in patients and to compare the quality of PET images acquired with a PET/MR device with those acquired with a PET/computed tomography (CT) scanner.
  
  
  METHODS
  Sequential PET/CT and PET/MR imaging was performed in 24 patients with neuroendocrine tumors using a single-injection/dual-imaging protocol. After intravenous injection of 68Ga-DOTATOC (mean, 120 MBq), PET/CT imaging including low-dose CT was performed at a mean time of 17 minutes post injection, and subsequently, PET/MR imaging including a Dixon sequence for attenuation correction was started at a mean time of 82 minutes post injection. The PET/CT and PET/MR images were analyzed visually using a 4-point scale for quality, coregistration, anatomical correlation, and lesion conspicuity. The standardized uptake value of background organs and focal lesions was measured and compared between the PET/CT and PET/MR acquisitions.
  
  
  RESULTS
  68Ga-DOTATOC PET acquired on the PET/MR delivered images with a good diagnostic quality (average visual rating PET/CT, 2.83; PET/MR, 2.08; P <; 0.01). The standardized uptake value of focal lesions did not differ between the PET/CT and PET/MR acquisitions (P >; 0.3) and correlated in a linear fashion (correlation coefficient ρ = 0.90). Lesion conspicuity was slightly, but significantly, higher on the PET/CT acquisitions (PET/CT, 2.71; PET/MR, 2.62; P = 0.01). Positron emission tomography/MR detected 153 of 157 lesions identified by PET/CT; however, there was no difference in sensitivity on a patient basis or organ system basis. Anatomical correlates for focal PET lesions could significantly more often be delineated using MR Dixon images compared with low-dose CT (average visual rating PET/CT, 1.78; PET/MR, 2.30; P <; 0.01). Coregistration of functional and morphological data was better on PET/MR compared with PET/CT, which, however, did not reach significance (average visual rating PET/CT, 2.17; PET/MR, 2.46; P = 0.10).
  
  
  CONCLUSIONS
  68Ga-DOTATOC PET/MR imaging is feasible in patients, with good image quality, and detectability of focal PET lesions was equivalent to PET/CT on a patient basis and organ system basis. Now, the clinical value of 68Ga-DOTATOC PET/MR with additional diagnostic MR protocols has to be evaluated against PET/CT with multiphase contrast-enhanced CT protocols in future studies.
authors: Department of Nuclear Medicine, Technische Universitaet Muenchen, Klinikum rechts der Isar, Muenchen, Germany. florian.gaertner@tum.de
authors: Florian C
authors: FC
authors: Gaertner
authors: Ambros J
authors: AJ
authors: Beer
authors: Michael
authors: M
authors: Souvatzoglou
authors: Matthias
authors: M
authors: Eiber
authors: Sebastian
authors: S
authors: Fürst
authors: Sybille I
authors: SI
authors: Ziegler
authors: Florian
authors: F
authors: Brohl
authors: Markus
authors: M
authors: Schwaiger
authors: Klemens
authors: K
authors: Scheidhauer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005240:Feasibility Studies; D005260:Female; D005710:Gallium Radioisotopes; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D018358:Neuroendocrine Tumors / Q000175:diagnosis*; D015282:Octreotide / Q000031:analogs & derivatives*; D009942:Organometallic Compounds; D049268:Positron-Emission Tomography / Q000379:methods*; D014057:Tomography, X-Ray Computed
chemical_list: C499142:Ga(III)-DOTATOC; D005710:Gallium Radioisotopes; D009942:Organometallic Compounds; D015282:Octreotide