T1ρ-MR imaging technique to distinguish four-layered zonal structure of articular cartilage for detecting early-onset osteoarthritis

Abstract

In order to evaluate the capacity of T1ρ-MRI(Magnetic Resonance Imaging) technique in distinguishing a four-layered zonal structure of articular cartilage for detecting the early-onset osteoarthritis (OA), eight 3-month-old female Danish landrace pigs, weighing 45.3 ± 5.5 kg, were used in this study. Two hind knees were randomly divided into two groups. IL-1β was injected into articular cavities in one group while physiological saline into another as a control one. Six hours later, the patellae were obtained for T1ρ-MRI and histological examination to distinguish the four-layered zonal structure of articular cartilages. The thickness of each layer and their percentages in the entire cartilage were measured on both T1ρ-MR images and the histological slices. T1ρ values of every layer were calculated from T1ρ-mapping images. In the result, the four-layered zonal structure of articular cartilage was displayed on both T1ρ-MR images and the histological slices. The ICC between these two methods was 0.981 for single measures (P=0.001), and 0.990 for average measures (P = 0.001). Compared with control patellae, T1ρ values significantly increased on the superficial and calcified layers in the IL-1β treated patellae (P=0.037). Therefore, this study demonstrates that the four-layered zonal structure of the articular cartilage is visibly displayed on the T1ρ-MR images. T1ρ-MRI technique can detect the earliest event of cartilage degeneration while these measurable changes are not shown in the histological slices. It is possible to use this technique for observing the effects of early interventions on the early-onset OA.