PET/MRI of metabolic activity in osteoarthritis: A feasibility study

J Magn Reson Imaging. 2017 Jun;45(6):1736-1745. doi: 10.1002/jmri.25529. Epub 2016 Oct 31.

Abstract

Purpose: 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.

Materials and methods: 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 of 18 F-fluoride or 18 F-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 in 18 F-fluoride uptake between bone abnormalities, BML, and osteophyte grades and adjacent cartilage grades on MRI were identified using Mann-Whitney U-tests.

Results: SUVmax in 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 on 18 F-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 SUVmax in 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).

Conclusion: 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.

Level of evidence: 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;45:1736-1745.

Keywords: PET/MRI; bone remodeling; osteoarthritis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Biomarkers / metabolism
  • Bone Diseases, Metabolic / complications
  • Bone Diseases, Metabolic / diagnosis*
  • Bone Diseases, Metabolic / metabolism*
  • Contrast Media / pharmacokinetics
  • Female
  • Fluorodeoxyglucose F18 / pharmacokinetics*
  • Humans
  • Image Enhancement / methods
  • Image Interpretation, Computer-Assisted / methods
  • Magnetic Resonance Imaging / methods*
  • Male
  • Multimodal Imaging / methods
  • Osteoarthritis, Knee / complications
  • Osteoarthritis, Knee / diagnostic imaging*
  • Osteoarthritis, Knee / metabolism*
  • Positron-Emission Tomography / methods*
  • Radiopharmaceuticals / pharmacokinetics
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Tissue Distribution

Substances

  • Biomarkers
  • Contrast Media
  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18