title: Qualitative and quantitative comparison of PET/CT and PET/MR imaging in clinical practice.
abstract: The aim of this study was to prospectively compare whole-body PET/MR imaging and PET/CT, qualitatively and quantitatively, in oncologic patients and assess the confidence and degree of inter- and intraobserver agreement in anatomic lesion localization.
  
  
  METHODS
  Fifty patients referred for staging with known cancers underwent PET/CT with low-dose CT for attenuation correction immediately followed by PET/MR imaging with 2-point Dixon attenuation correction. PET/CT scans were obtained according to standard protocols (56 ± 20 min after injection of an average 367 MBq of (18)F-FDG, 150 MBq of (68)Ga-DOTATATE, or 333.8 MBq of (18)F-fluoro-ethyl-choline; 2.5 min/bed position). PET/MR was performed with 5 min/bed position. Three dual-accredited nuclear medicine physicians/radiologists identified the lesions and assigned each to an exact anatomic location. The image quality, alignment, and confidence in anatomic localization of lesions were scored on a scale of 1-3 for PET/CT and PET/MR imaging. Quantitative analysis was performed by comparing the standardized uptake values. Intraclass correlation coefficients and the Wilcoxon signed-rank test were used to assess intra- and interobserver agreement in image quality, alignment, and confidence in lesion localization for the 2 modalities.
  
  
  RESULTS
  Two hundred twenty-seven tracer-avid lesions were identified in 50 patients. Of these, 225 were correctly identified on PET/CT and 227 on PET/MR imaging by all 3 observers. The confidence in anatomic localization improved by 5.1% when using PET/MR imaging, compared with PET/CT. The mean percentage interobserver agreement was 96% for PET/CT and 99% for PET/MR imaging, and intraobserver agreement in lesion localization across the 2 modalities was 93%. There was 10% (5/50 patients) improvement in local staging with PET/MR imaging, compared with PET/CT.
  
  
  CONCLUSIONS
  In this first study, we show the effectiveness of whole-body PET/MR imaging in oncology. There is no statistically significant difference between PET/MR imaging and PET/CT in respect of confidence and degree of inter- and intraobserver agreement in anatomic lesion localization. The PET data on both modalities were similar; however, the observed superior soft-tissue resolution of MR imaging in head and neck, pelvis, and colorectal cancers and of CT in lung and mediastinal nodal disease points to future tailored use in these locations.
authors: Institute of Nuclear Medicine, University College London Hospital NHS Foundation Trust, London NW1 2BU, United Kingdom.
authors: Khalsa Z
authors: KZ
authors: Al-Nabhani
authors: Rizwan
authors: R
authors: Syed
authors: Sofia
authors: S
authors: Michopoulou
authors: Jokha
authors: J
authors: Alkalbani
authors: Asim
authors: A
authors: Afaq
authors: Emmanouil
authors: E
authors: Panagiotidis
authors: Celia
authors: C
authors: O'Meara
authors: Ashley
authors: A
authors: Groves
authors: Peter
authors: P
authors: Ell
authors: Jamshed
authors: J
authors: Bomanji
mesh_terms: D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D009367:Neoplasm Staging / Q000379:methods; D015588:Observer Variation; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods*; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*; D051598:Whole Body Imaging
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: PET/CT; PET/MR imaging; cancer; intraobserver agreement