title: PET/MRI of metabolic activity in osteoarthritis: A feasibility study.
abstract: To evaluate positron emission tomography / magnetic resonance imaging (PET/MRI) knee imaging to detect and characterize osseous metabolic abnormalities and correlate PET radiotracer uptake with osseous abnormalities and cartilage degeneration observed on MRI.
  
  
  
  Both knees of 22 subjects with knee pain or injury were scanned at one timepoint, without gadolinium, on a hybrid 3.0T PET-MRI system following injection of18F-fluoride or18F-fluorodeoxyglucose (FDG). A musculoskeletal radiologist identified volumes of interest (VOIs) around bone abnormalities on MR images and scored bone marrow lesions (BMLs) and osteophytes using a MOAKS scoring system. Cartilage appearance adjacent to bone abnormalities was graded with MRI-modified Outerbridge classifications. On PET standardized uptake values (SUV) maps, VOIs with SUV greater than 5 times the SUV in normal-appearing bone were identified as high-uptake VOI (VOIHigh). Differences in18F-fluoride uptake between bone abnormalities, BML, and osteophyte grades and adjacent cartilage grades on MRI were identified using Mann-Whitney U-tests.
  
  
  
  SUVmaxin all subchondral bone lesions (BML, osteophytes, sclerosis) was significantly higher than that of normal-appearing bone on MRI (P < 0.001 for all). Of the 172 high-uptake regions on18F-fluoride PET, 63 (37%) corresponded to normal-appearing subchondral bone on MRI. Furthermore, many small grade 1 osteophytes (40 of 82 [49%]), often described as the earliest signs of osteoarthritis (OA), did not show high uptake. Lastly, PET SUVmaxin subchondral bone adjacent to grade 0 cartilage was significantly lower compared to that of grades 1-2 (P < 0.05) and grades 3-4 cartilage (P < 0.001).
  
  
  
  PET/MRI can simultaneously assess multiple early metabolic and morphologic markers of knee OA across multiple tissues in the joint. Our findings suggest that PET/MR may detect metabolic abnormalities in subchondral bone, which appear normal on MRI.
  
  
  
  2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;45:1736-1745.
authors: Department of Radiology, Stanford University, Stanford, California, USA.
authors: Feliks
authors: F
authors: Kogan
authors: Department of Radiology, Stanford University, Stanford, California, USA.
authors: Audrey P
authors: AP
authors: Fan
authors: Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, Canada.
authors: Emily J
authors: EJ
authors: McWalter
authors: Department of Radiology & Nuclear Medicine, Erasmus MC, University Medical Center, Rotterdam, Netherlands.
authors: Edwin H G
authors: EHG
authors: Oei
authors: Department of Radiology, Stanford University, Stanford, California, USA.
authors: Andrew
authors: A
authors: Quon
authors: Department of Radiology, Stanford University, Stanford, California, USA.|Department of Bioengineering, Stanford University, Stanford, California, USA.|Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA.
authors: Garry E
authors: GE
authors: Gold
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D001851:Bone Diseases, Metabolic / Q000150:complications / Q000175:diagnosis* / Q000378:metabolism*; D003287:Contrast Media / Q000493:pharmacokinetics; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D064847:Multimodal Imaging / Q000379:methods; D020370:Osteoarthritis, Knee / Q000150:complications / Q000000981:diagnostic imaging* / Q000378:metabolism*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D015415:Biomarkers; D003287:Contrast Media; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: PET/MRI; bone remodeling; osteoarthritis