Convincing evidence for magic angle less-sensitive quantitative T1ρ imaging of articular cartilage using the 3D ultrashort echo time cones adiabatic T1ρ (3D UTE cones-AdiabT1ρ ) sequence.

Abstract

To investigate the magic angle effect in three-dimensional ultrashort echo time Cones Adiabatic T1ρ (3D UTE Cones-AdiabT1ρ ) imaging of articular cartilage at 3T. The magic angle effect was investigated by repeated 3D UTE Cones-AdiabT1ρ imaging of eight human patellar samples at five angular orientations ranging from 0° to 90° relative to the B0 field. Cones continuous wave T1ρ (Cones-CW-T1ρ ) and Cones- sequences were also applied for comparison. Cones-AdiabT1ρ , Cones-CW-T1ρ and Cones- values were measured for four regions of interest (ROIs) (10% superficial layer, 60% transitional layer, 30% radial layer, and a global ROI) for each sample at each orientation to evaluate their angular dependence. 3D UTE Cones-AdiabT1ρ values increased from the radial layer to the superficial layer for all angular orientations. The superficial layer showed the least angular dependence (around 4.4%), while the radial layer showed the strongest angular dependence (around 34.4%). Cones-AdiabT1ρ values showed much reduced magic angle effect compared to Cones-CW-T1ρ and Cones- values for all four ROIs. On average over eight patellae, Cones-AdiabT1ρ values increased by 27.2% (4.4% for superficial, 23.8% for transitional, and 34.4% for radial layers), Cones-CW-T1ρ values increased by 76.9% (11.3% for superficial, 59.1% for transitional, and 117.8% for radial layers), and Cones- values increased by 237.5% (87.9% for superficial, 262.9% for transitional, and 327.3% for radial layers) near the magic angle. The 3D UTE Cones-AdiabT1ρ sequence is less sensitive to the magic angle effect in the evaluation of articular cartilage compared to Cones- and Cones-CW-T1ρ .