Principal Component Analysis of Simultaneous PET‐MRI Reveals Patterns of Bone–Cartilage Interactions in Osteoarthritis

Abstract

Background Bone–cartilage interactions have been implicated in causing osteoarthritis (OA). Purpose To use [18F]‐NaF PET‐MRI to 1) develop automatic image processing code in MatLab to create a model of bone–cartilage interactions and 2) find associations of bone–cartilage interactions with known manifestations of OA. Study Type Prospective study aimed to evaluate a data analysis method. Population Twenty‐nine patients with knee pain or joint stiffness. Field Strength/Sequence 3T MRI (GE), 3D CUBE FSE, 3D combined T1ρ/T2 MAPSS, [18F]‐sodium fluoride, SIGNA TOF (OSEM). Assessment Correlation between MRI (cartilage) and PET (bone) quantitative parameters, bone–cartilage interactions model described by modes of variation as derived by principal component analysis (PCA), WORMS scoring on cartilage lesions, bone marrow abnormalities, subchondral cysts. Statistical Tests Linear regression, Pearson correlation. Results Mode 1 was a positive predictor of the bone abnormality score (P = 0.0003, P = 0.001, P = 0.0007) and the cartilage lesion score (P = 0.03, P = 0.01, P = 0.02) in the femur, tibia, and patella, respectively. For the cartilage lesion scores, mode 5 was the most important positive predictor in the femur (P = 3.9E‐06), and mode 2 were predictors, significant negative predictor in the tibia (P = 0.007). In the patella, mode 1 was a significant positive predictor of the bone abnormality score (P = 0.0007). Data Conclusion By successfully building an automatic code to create a bone–cartilage interface, we were able to observe dynamic relationships between biochemical changes in the cartilage accompanied with bone remodeling, extended to the whole knee joint instead of simple colocalized observations, shedding light on the interactions that occur between bone and cartilage in OA. Evidence Level: 3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2020;52:1462–1474.

[18F]NaF PET-MRI provides direct in-vivo evidence of the association between bone metabolic activity and adjacent synovitis in knee osteoarthritis: a cross-sectional study

“…The capability that PET-MRI provides to assess the functional relationship between different joint tissues allows us to move away from an imaging focus on a single joint tissue and towards an integrated whole-joint quantitative imaging assessment. The promise of PET-MRI here has been highlighted by previous studies looking at bone-cartilage interactions in OA 26,34 , now extended by the current work to bonesynovium interactions. In addition, PET-MRI has potential utility beyond the knee as exemplified by a recent study assessing correlation with patient symptoms in hip OA 35 .…”

Local Patterns in 2‐Year T1ρ and T2 Changes of Hip Cartilage Are Related to Sex and Functional Data: A Prospective Evaluation on Hip Osteoarthritis Participants

“…However, these were not direct correlations (e.g., T 1ρ PC1 correlated with T 2 PC1), as demonstrated in cross-sectional PCA of knee T 1ρ and T 2 relaxometry maps. 39 This may indicate that T 1ρ and T 2 relaxation times over 2 years progress at different paces or in different patterns within hip cartilage.…”

Latest advancements in imaging techniques in OA

“…Increased [ 18 F]NaF PET uptake has been shown to correlate with increased adjacent cartilage T2 and T1ρ relaxation times in OA at multiple disease stages in the knee and the hip. 42 , 47 – 49 In addition, [ 18 F]NaF PET-MRI imaging, utilizing [ 18 F]NaF PET as a marker of bone metabolism and dynamic contrast-enhanced (DCE)-MRI as a marker of synovial inflammation, was synergistically utilized to provide direct in vivo evidence of associations between synovitis and adjacent metabolic bone activity and osteophyte formations. 50 …”