[¹⁸F]‐Sodium Fluoride PET/MR Imaging for Bone–Cartilage Interactions in Hip Osteoarthritis: A Feasibility Study

Abstract

This study characterized the distribution of [ 18 F]-sodium fluoride (NaF) uptake and blood flow in the femur and acetabulum in hip osteoarthritis (OA) patients to find associations between bone remodeling and cartilage composition in the presence of morphological abnormalities using simultaneous positron emission tomography and magnetic resonance imaging (PET/MR), quantitative magnetic resonance imaging (MRI) and femur shape modeling. Ten patients underwent a [ 18 F]-NaF PET/MR dynamic scan of the hip simultaneously with: (i) fast spin-echo CUBE for morphology grading and (ii) T 1ρ /T 2 magnetization-prepared angle-modulated partitioned k-space spoiled gradient echo snapshots for cartilage, bone segmentation, bone shape modeling, and T 1ρ /T 2 quantification. The standardized uptake values (SUVs) and Patlak kinetic parameter (K pat ) were calculated for each patient as PET outcomes, using an automated post-processing pipeline. Shape modeling was performed to extract the variations in bone shapes in the patients. Pearson's correlation coefficients were used to study the associations between bone shapes, PET outcomes, and patient reported pain. Direct associations between quantitative MR and PET evidence of bone remodeling were established in the acetabulum and femur. Associations of shaft thickness with SUV in the femur (p = 0.07) and K pat in the acetabulum (p = 0.02), cam deformity with acetabular score (p = 0.09), osteophytic growth on the femur head with K pat (p = 0.01) were observed. Pain had increased correlations with SUV in the acetabulum (p = 0.14) and femur (p = 0.09) when shaft thickness was accounted for. This study demonstrated the ability of [ 18 F]-NaF PET-MRI, 3D shape modeling, and quantitative MRI to investigate cartilage-bone interactions and bone shape features in hip OA, providing potential investigative tools to diagnose OA.

Novel Musculoskeletal and Orthopedic Applications of 18F-Sodium Fluoride PET

“…NaF has shown success in visualizing changes associated with joint degeneration such as in osteoarthritis (OA) and temporomandibular disorder (TMD). [30][31][32][33][34][35][36][37][38][39] Both FDG and NaF activities at the knee were assessed in 97 subjects in a study by Al-Zaghal and colleagues, 40 who found uptake of both tracers was correlated with body mass index. Studies from the same group have similarly found associations between body mass index and NaF uptake at the sacroiliac and hip joints, which are often involved in OA.…”

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

“…Kobayashi et al and Draper et al found that not all increased uptakes corresponded to structural abnormalities on MRI, suggesting that NaF‐PET can detect bone abnormalities even before MRI 15,19 . Tibrewala et al found direct associations between quantitative MRI and PET evidence of bone remodeling in hip OA 13 . In a study of anterior cruciate ligament (ACL)‐injured patients using PET‐MRI, Kogan et al found increased tracer uptake and cartilage T 2 relaxation in ACL‐reconstructed knees, as compared to the contralateral knees.…”

“…Thus, magnetic resonance imaging (MRI) has been used to investigate cartilage degeneration biomarkers using MRI‐based T 1ρ and T 2 relaxation times, which assess proteoglycan and collagen content in cartilage, respectively, and these have been found to have differences between normal and OA patients 9–11 . Additionally, [ 18 F]‐NaF (sodium fluoride) positron emission tomography (PET)‐MRI has previously been used in investigating bone–cartilage relationships, owing to its simultaneous functional and structural imaging capabilities, proving itself a feasible method to study early OA 12–15 . 18‐Fluoride (18‐F) is a highly sensitive bone imaging agent that is extracted by the blood system in the body in proportion to the osteoblastic activity (reflecting blood flow and bone remodeling), and has been used as a PET tracer for multiple musculoskeletal diseases, including OA 16–18 .…”

“…[9][10][11] Additionally, [ 18 F]-NaF (sodium fluoride) positron emission tomography (PET)-MRI has previously been used in investigating bone-cartilage relationships, owing to its simultaneous functional and structural imaging capabilities, proving itself a feasible method to study early OA. [12][13][14][15] 18-Fluoride (18-F) is a highly sensitive bone imaging agent that is extracted by the blood system in the body in proportion to the osteoblastic activity (reflecting blood flow and bone remodeling), and has been used as a PET tracer for multiple musculoskeletal diseases, including OA. [16][17][18] Savic et al found that increases in cartilage T 1ρ relaxation times (indicating degenerative changes) were associated with increased turnover in the adjoining bone as imaged by [ 18 F]-NaF.…”

“…15,19 Tibrewala et al found direct associations between quantitative MRI and PET evidence of bone remodeling in hip OA. 13 In a study of anterior cruciate ligament (ACL)-injured patients using PET-MRI, Kogan et al found increased tracer uptake and cartilage T 2 relaxation in ACL-reconstructed knees, as compared to the contralateral knees. Moreover, they observed a spatial relationship between cartilage T 2 and SUV, where increased tracer uptake in the subchondral bone adjacent to an area of increased cartilage relaxation time was observed.…”