Comparative T2 and T1 mapping of patellofemoral cartilage under in situ mechanical loading with prospective motion correction

PurposeTo demonstrate improved T-2 and T-1 mapping of patellofemoral cartilage with in situ loading by means of prospective motion correction and to assess load-induced changes in healthy subjects. Materials and MethodsEstablished T-2 and T-1 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-2 and T-1 changes were evaluated through measurements with axial loads of 0/20/40kg. ResultsWith 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-2 mapping. The acquired relaxation maps suggested a T-2/T-1 decrease in superficial cartilage and a T-2/T-1 increase in deep cartilage under loading. However, in the quantitative group evaluation of the lateral patellar facet, only T-1 in superficial cartilage was significantly changed by loading (P 0.05), while no significant T-2 differences for the three loading conditions were observed (P 0.3). ConclusionProspective motion correction enables T-2 and T-1 mapping of patellofemoral cartilage with in situ loading and a comparison of the two contrasts in terms of their response to mechanical loading. T-1 is a more sensitive marker for load-induced patellar cartilage changes than T-2. Level of Evidence: 3 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:452-460