title: Comparison of whole-body PET/CT and PET/MRI in breast cancer patients: lesion detection and quantitation of 18F-deoxyglucose uptake in lesions and in normal organ tissues.
abstract: OBJECTIVE
  To compare the performance of PET/MRI imaging using MR attenuation correction (MRAC) (DIXON-based 4-segment -map) in breast cancer patients with that of PET/CT using CT-based attenuation correction and to compare the quantification accuracy in lesions and in normal organ tissues.
  
  
  METHODS
  A total of 36 patients underwent a whole-body PET/CT scan 1h after injection and an average of 62 min later a second scan using a hybrid PET/MRI system. PET/MRI and PET/CT were compared visually by rating anatomic allocation and image contrast. Regional tracer uptake in lesions was quantified using volumes of interest, and maximal and mean standardized uptake values (SUVmax and SUVmean, respectively) were calculated. Metabolic tumor volume (MTV) of each lesion was computed on PET/MRI and PET/CT. Tracer uptake in normal organ tissue was assessed as SUVmax and SUVmean in liver, spleen, left ventricular myocardium, lung, and muscle.
  
  
  RESULTS
  Overall 74 FDG positive lesions were visualized by both PET/CT and PET/MRI. No significant differences in anatomic allocation scores were found between PET/CT and PERT/MRI, while contrast score of lesions on PET/MRI was significantly higher. Both SUVmax and SUVmean of lesions were significantly higher on PET/MRI than on PET/CT, with strong correlations between PET/MRI and PET/CT data (ρ=0.71-0.88). MTVs of all lesions were 4% lower on PET/MRI than on PET/CT, but no statistically significant difference was observed, and an excellent correlation between measurements of MTV with PET/MRI and PET/CT was found (ρ=0.95-0.97; p<0.0001). Both SUVmax and SUVmean were significantly lower by PET/MRI than by PET/CT for lung, liver and muscle, no significant difference was observed for spleen, while either SUVmax and SUVmean of myocardium were significantly higher by PET/MRI. High correlations were found between PET/MRI and PET/CT for both SUVmax and SUVmean of the left ventricular myocardium (ρ=0.91; p<0.0001), while moderate correlations were found for the other normal organ tissues (ρ=0.36-0.61; p<0.05).
  
  
  CONCLUSIONS
  PET/MRI showed equivalent performance in terms of qualitative lesion detection to PET/CT. Despite significant differences in tracer uptake quantification, due to either methodological and biological factors, PET/MRI and PET/CT measurements in lesions and normal organ tissues correlated well. This study demonstrates that integrated whole-body PET/MRI is feasible in a clinical setting with high quality and in a short examination time.
authors: Dipartimento di Medicina e Chirurgia, Università degli Studi di Salerno, Italy. Electronic address: lpace@unisa.it.
authors: Leonardo
authors: L
authors: Pace
authors: IRCCS-SDN, Napoli, Italy. Electronic address: enicolai@sdn-napoli.it.
authors: Emanuele
authors: E
authors: Nicolai
authors: Dipartimento di Scienze Biomediche Avanzate, Università degli Studi di Napoli Federico II, Italy. Electronic address: angelo_luongo@libero.it.
authors: Angelo
authors: A
authors: Luongo
authors: IRCCS-SDN, Napoli, Italy. Electronic address: maiello@sdn-napoli.it.
authors: Marco
authors: M
authors: Aiello
authors: IRCCS-SDN, Napoli, Italy. Electronic address: onofriocatalano@yahoo.it.
authors: Onofrio A
authors: OA
authors: Catalano
authors: Dipartimento di Studi delle Istituzioni e dei Sistemi Territoriali, Università degli Studi Parthenope di Napoli, Italy. Electronic address: andrea.soricelli@uniparthenope.it.
authors: Andrea
authors: A
authors: Soricelli
authors: Dipartimento di Scienze Biomediche Avanzate, Università degli Studi di Napoli Federico II, Italy. Electronic address: marsalva@unina.it.
authors: Marco
authors: M
authors: Salvatore
mesh_terms: D001943:Breast Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D057054:Molecular Imaging / Q000379:methods; D064847:Multimodal Imaging / Q000379:methods; D009928:Organ Specificity; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D014057:Tomography, X-Ray Computed / Q000379:methods*; D051598:Whole Body Imaging / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: Breast cancer; Hybrid imaging; MTV; Oncology; PET/CT; PET/MRI; SUV