Magnetom symphony quantum 1.5 t scanner

Primary outcome measures for this study, T2 relaxation time (T2) mapping (milliseconds, ms)
and the delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC index, ms), were measured using a Siemens Magnetom Symphony Quantum 1.5-T scanner (Siemens AG, Medical Solutions, Erlangen, Germany). These methods provide information on the response of tibiofemoral cartilage to physiological loading (21, 28) . T2 is a surrogate for the properties of the collagen network with lower values corresponding to better integrity and orientation of the collagen fibres and the hydration of the articular cartilage (18, 30). dGEMRIC index measures estimated GAG content of the knee articular cartilage with higher values

Primary outcomes for this study were T2 relaxation time (T2) mapping (milliseconds, ms) and delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC index, ms). Images were taken using a Siemens Magnetom Symphony Quantum 1.5-T scanner (Siemens AG, Medical Solutions, Erlangen, Germany). Single sagittal slice images from the centre of the medial and lateral femoral condyles were taken from the knee with the highest K/L grade (affected knee). In cases of identical grading bilaterally, the right knee was imaged. Images were manually segmented using an in-house MATLAB application with built-in motion correction for dGEMRIC (Mathworks, Inc. Natick, MA, USA). In this study we divided the femoral cartilage into three region of interests (ROIs); anterior, central and posterior (Fig. 2). dGEMRIC indices were corrected for BMI 27 . Precision, scan-rescan, (CV RMS ) of dGEMRIC in asymptomatic subjects is 7% for fullthickness ROIs and 5% for bulk cartilage 28 . In our laboratory, the inter-observer error (CV RMS ) for T2 full-thickness ROIs was 1.3e3.3% and 2.8e4.0% for dGEMRIC index. The full MRI protocol and example images are provided in the online supplemental material.