Qualitative and quantitative ultrashort echo time (UTE) imaging of cortical bone

Abstract

We describe the use of two-dimensional ultrashort echo time (2D UTE) sequences with minimum TEs of 8 μs to image and quantify cortical bone on a clinical 3T scanner. An adiabatic inversion pulse was used for long T 2 water and fat signal suppression. Adiabatic inversion prepared UTE acquisitions with varying TEs were used for T 2 ∗ measurement. Saturation recovery UTE acquisitions were used for T 1 measurement. Bone water concentration was measured with the aid of an external reference phantom. UTE techniques were evaluated on cadaveric specimens and healthy volunteers. A signal-to-noise ratio of around 30, contrast-to-noise ratio of around 27/20 between bone and muscle/fat were achieved in tibia in vivo with a nominal voxel size of 0.23 × 0.23 × 6.0 mm 3 in a scan time of 5 min. A mean T 1 of 223 ± 11 ms and mean T 2 ∗ of 390 ± 19 μs were found. Mean bone water concentrations of 23.3 ± 1.6% with UTE and 21.7 ± 1.3% with adiabatic inversion prepared UTE sequences were found in tibia in five normal volunteers. The results show that in vivo qualitative and quantitative evaluation of cortical bone is feasible with 2D UTE sequences.