title: Comparative characteristics of quantitative indexes for 18F-FDG uptake and metabolic volume in sequentially obtained PET/MRI and PET/CT.
abstract: OBJECTIVE
  The purpose of this study was to compare quantitative indexes for fluorine-18 fluorodeoxyglucose uptake and metabolic volume between PET/MRI and PET/CT.
  
  
  METHODS
  Sixty-six patients with solid tumors (32 with lung cancer and 34 with pancreatic cancer) who underwent sequential fluorine-18 fluorodeoxyglucose PET/MRI and PET/CT were retrospectively enrolled. On PET images, maximum and peak standardized uptake values (SUVmax and SUVpeak, respectively), and maximum tumor-to-liver ratio (TLRmax) were measured. Metabolic tumor volume (MTV) and total-lesion glycolysis (TLG) with margin thresholds of 50% SUVmax and SUV 2.5 (MTV50%, MTV2.5; TLG50%, TLG2.5, respectively) were compared between PET/MRI and PET/CT, with patients classified into two groups using imaging protocol (the PET/MRI-first and PET/CT-first groups).
  
  
  RESULTS
  There were significant correlations of all tested indexes between PET/MRI and PET/CT (r=0.867-0.987, P<0.001). SUVmax and SUVpeak were lower on PET/MRI regardless of imaging protocol (P<0.001 in the PET/MRI-first group). In contrast, TLRmax exhibited reverse results between the PET/MRI-first and PET/CT-first groups. MTV50% and TLG values varied between PET/MRI and PET/CT, as well as between the PET/MRI-first and PET/CT-first groups. However, MTV2.5 was relatively robust against imaging protocol and modality.
  
  
  CONCLUSIONS
  There are significant correlations of the quantitative indexes between PET/MRI and PET/CT. However, uptake indexes of SUVmax and SUVpeak are lower on PET/MRI than on PET/CT, and volumetric indexes of MTV50% and TLG values also exhibited significant differences. It may be suggested that TLRmax and MTV2.5 are relatively more appropriate indexes than others when PET/MRI and PET/CT are used interchangeably.
authors.affiliation: aDepartment of Nuclear Medicine, Hanyang University Medical Center Departments of bNuclear Medicine cRadiology dCancer Research Institute, College of Medicine, Seoul National University, Seoul, Korea.
authors.forename: Soo Jin
authors.initials: SJ
authors.lastname: Lee
authors.forename: Jin Chul
authors.initials: JC
authors.lastname: Paeng
authors.forename: Jin Mo
authors.initials: JM
authors.lastname: Goo
authors.forename: Jeong Min
authors.initials: JM
authors.lastname: Lee
authors.forename: Gi Jeong
authors.initials: GJ
authors.lastname: Cheon
authors.forename: Dong Soo
authors.initials: DS
authors.lastname: Lee
authors.forename: June-Key
authors.initials: JK
authors.lastname: Chung
authors.forename: Keon Wook
authors.initials: KW
authors.lastname: Kang
mesh_terms: D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D006019:Glycolysis; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods* / Q000706:statistics & numerical data; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D000072078:Positron Emission Tomography Computed Tomography; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012189:Retrospective Studies
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18