Xr 80 200 gradient coil

Magnetic resonance images from both limbs were acquired using either a Siemens Magnetom TIM Trio 3 Tesla scanner with a 4-channel Siemens large flex coil (516 mm x 224 mm, Siemens, Munich, Germany) or a Siemens Magnetom Prisma 3T PowerPack scanner with a XR 80/200 gradient coil (60 cm x 213 cm, Siemens, Munich, Germany). Strong inter-scanner reliability for absolute agreement has been previously determined for T1ρ relaxation times in the entire medial (ICC _2,1=0.99) and lateral (ICC _2,1=0.96) weight bearing regions of the femoral condyle in a separate cohort of 6 knees assessed in both scanners approximately 45 days apart.(25 (link)) Upon arrival to the imaging center, participants remained seated for 30 minutes to unload the knee cartilage (31 (link)). We used a T1ρ prepared three-dimensional Fast Low Angle Shot (FLASH) with a spin-lock power at 500Hz, five different spin-lock durations (40, 30, 20, 10, 0 ms) and a voxel size of 0.8mm x 0.4mm x 3mm (field of view= 288mm, slice thickness=3.0mm, TR= 9.2ms, 160 × 320 matrix, gap= 0mm, flip angle=10°, echo-train duration time= 443ms, phase encode direction of anterior/posterior) (32 , 33 ).

T1 MRI outcomes were acquired with a Siemens Magnetom TIM Trio 3T scanner using a 4-channel Siemens large flex coil (516 mm × 224 mm, Siemens, Munich, Germany) for 18 of the 21 participants. Due to a MRI systems upgrade in our Biomedical Research Imaging Center, the 12 month T1ρ MRI outcomes for 3 of the 21 participants were acquired using a Siemens Magnetom Prisma 3T PowerPack scanner with a XR 80/200 gradient coil (60 cm × 213 cm, Siemens, Munich, Germany). Inter-scanner reliability was assessed in 6 knees using intra-class correlation coefficients (ICC), which were found to be within an acceptable range (ICC≥0.75) for all regions of interest. Additionally, all T1ρ relaxation times in the ACLR limb were normalized to the regions of interest in the uninjured contralateral limb for each participant thereby minimizing any effect from utilizing multiple MRI scanners. Prior to acquiring MR images, participants remained seated for 30 minutes to unload the knee cartilage.(27 (link)) We used a T1ρ prepared three-dimensional Fast Low Angle Shot (FLASH) with a spin-lock power at 500Hz, five different spin-lock durations (40, 30, 20,10, 0 ms) and a voxel size of 0.8mm × 0.4mm × 3mm (field of view= 288mm, slice thickness=3.0mm, TR= 9.2ms, 160 × 320 matrix, gap= 0mm, flip angle=10°, echo-train duration time= 443ms, phase encode direction of anterior/posterior).