The possibilities of magnetic resonance imaging in the diagnosis of microstructural changes in articular cartilage in osteoarthritis

Aim. To assess the potential of the magnetic resonance imaging (PDFS) weighted by the proton density in the diagnosis of microstructural changes in articular cartilage (AC) in osteoarthritis (OA) based on the analysis of the variability of the proton density (PD).

Materials and methods. 62 patients with OA and 8 volunteers without OA were examined. All patients underwent MRI of knee joints on a high-field tomograph with a magnetic field strength of 1.5 Tesla. Semi-quantitative measurements of joint tissues based on the WORMS protocol were used to evaluate MR images. To evaluate PD manually, segmentation of PDFS-weighted images of the medial condyle of the knee joint was performed. The proton density was estimated from a 3-D histogram on a scale of 0 to 255.

Results. At the first stage of OA, a decrease in the density of H⁺ in the peripheral zone of AC was observed, but was retained in the contact part experiencing the maximum static-dynamic loads. In stage II of OA, a significant progressive decrease in the H⁺-dtensity peaks in AC regions undergoing lower loads was observed, while maintaining high spectral peaks in the region of increased friction. III stage of gonarthrosis was characterized by a decrease in the entire plan of H⁺-spectrum, especially in the load regions of AC. At the IV stage of OA, a global decrease in the intensity of PD over the entire surface of the cartilaginous plate was observed.

Conclusions. The revealed regularity of changes in the proton density spectrum reflects the well-known degenerative process in AC with OA. This property of proton-weighted MR images can be used in the assessment of microstructural changes in AC in OA.