Three‐dimensional ultrashort echo time imaging with tricomponent analysis for human cortical bone

Abstract

Purpose:To investigate tricomponent analysis of human cortical bone using a multipeak fat signal model with 3D ultrashort TE Cones sequences on a clinical 3T scanner. Methods: Tricomponent fitting of bound water, pore water, and fat content using a multipeak fat spectra model was proposed for 3D ultrashort TE imaging of cortical bone. Three-dimensional ultrashort TE Cones acquisitions combined with tricomponent analysis were used to investigate bound and pore water T * 2 and fractions, as well as fat T * 2 and fraction in cortical bone. Feasibility studies were performed on 9 human cortical bone specimens with regions of interest selected from the endosteum to the periosteum in 4 circumferential regions. Microcomputed tomography studies were performed to measure bone porosity and bone mineral density for comparison and validation of the bound and pore water analyses. Results: The oscillation of the signal decay was well-fitted with the proposed tricomponent model. The sum of the pore water and fat fractions from tricomponent analysis showed a high correlation with microcomputed tomography porosity (R = 0.74, P < 0.01). Estimated bound-water fraction also demonstrated a high correlation with bone mineral density (R = 0.70, P < 0.01). Conclusion: Tricomponent analysis significantly improves the estimation of boundwater and pore-water fractions in human cortical bone. K E Y W O R D Sbound water, multipeak fat spectral model, pore water, T * 2 , UTE

Correlations of cortical bone microstructural and mechanical properties with water proton fractions obtained from ultrashort echo time (UTE) MRI tricomponent T2* model

“…This tricomponent T2* fitting model has been examined by scanning entire cross‐sections of eight tibial cortical bone using a clinical knee coil on a clinical 3 T scanner. Estimated water fractions by the tricomponent T2* fitting demonstrated improved correlations with μCT‐based porosity compared with bicomponent analyses . It is hypothesized that providing higher correlations with bone porosity by tricomponent T2* analysis can also lead to an improved correlation with bone mechanical properties.…”

“…From recently advanced MRI techniques, ultrashort echo time (UTE) MRI can image cortical bone, thus allowing for quantitative assessment of cortical bone. 3,4,[6][7][8][9][10][11] Using UTE-MRI techniques, signal can be acquired quickly (tens of microseconds) after radiofrequency (RF) excitation and before a major decay in transverse magnetization.…”

“…Estimated water fractions by the tricomponent T2* fitting demonstrated improved correlations with μCT-based porosity compared with bicomponent analyses. 8 It is hypothesized that providing higher correlations with bone porosity by tricomponent T2* analysis can also lead to an improved correlation with bone mechanical properties. However, the relationship between tricomponent T2* analyses and mechanical properties of cortical bone has not been investigated.…”

Fat suppression for ultrashort echo time imaging using a novel soft‐hard composite radiofrequency pulse

“…Such efficient fat-signal suppression may improve MRI-based bone assessments [25][26][27] and reduce the need for extensive scans for sophisticated multicomponent signal analysis. 28 The proposed soft-hard composite pulse can preserve the short T 2 signals while suppressing the fat components, thus providing much higher contrast for short T 2 tissues than the non-fat-suppressed images. The soft-hard pulse is relatively sensitive to the B 0 field inhomogeneity because of the narrow bandwidth of the soft pulse.…”

“…Significantly higher SSRs were achieved with the composite pulse, especially for short T 2 tissues. Such efficient fat‐signal suppression may improve MRI‐based bone assessments and reduce the need for extensive scans for sophisticated multicomponent signal analysis …”