Comparative T 2 and T 1ρ mapping of patellofemoral cartilage under in situ mechanical loading with prospective motion correction

To demonstrate improved T and T mapping of patellofemoral cartilage with in situ loading by means of prospective motion correction and to assess load-induced changes in healthy subjects. Established T and T mapping sequences were augmented with prospective motion correction based on optical tracking. Protocols were optimized for robust imaging of the patellofemoral cartilage at a field strength of 3T. Subjects were positioned in the scanner with knee flexion and in situ loading of the patellofemoral joint was performed with a pneumatic loading device. In a pilot study on a cohort of 10 healthy subjects, load-induced T and T changes were evaluated through measurements with axial loads of 0/20/40 kg. With prospective motion correction and additional lipid saturation, motion artifacts in patellofemoral cartilage magnetic resonance imaging (MRI) with in situ loading could be notably decreased, as demonstrated for T mapping. The acquired relaxation maps suggested a T /T decrease in superficial cartilage and a T /T increase in deep cartilage under loading. However, in the quantitative group evaluation of the lateral patellar facet, only T in superficial cartilage was significantly changed by loading (P ≤ 0.05), while no significant T differences for the three loading conditions were observed (P ≥ 0.3). Prospective motion correction enables T and T mapping of patellofemoral cartilage with in situ loading and a comparison of the two contrasts in terms of their response to mechanical loading. T is a more sensitive marker for load-induced patellar cartilage changes than T . 3 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:452-460.