Three-dimensional radial ultrashort echo-time imaging with T₂ adapted sampling

The application of 3D radial sampling of the free-induction decay to proton ultrashort echo-time (UTE) imaging is reported. The effects of T2 decay during signal acquisition on the 3D radial point-spread function are analyzed and compared to 2D radial and 1D sampling, it is found that in addition to the use of ultrashort TE, the proper choice of the acquisition-window duration T _AQ is essential for imaging short-T₂ components. For 3D radial sampling, a maximal signal-to-noise ratio (SMR) with negligible decay-induced loss in spatial resolution is obtained for an acquisition-window duration of T_AQ ≈ 0.69 T₂. For 2D and 1D sampling, corresponding values are derived as well. Phantom measurements confirm the theoretical findings and demonstrate the impact of different acquisition-window durations on SNR and spatial resolution for a given T₂ component. In vivo scans show the potential of 3D UTE imaging with T₂-adapted sampling for musculoskeletal imaging using standard MR equipment The visualisation of complex anatomy is demonstrated by extracting curved slices from the isotropicalty resolved 3D UTE image data.