T1 Correlates Age: A Short-TE MR Relaxometry Study in vivo on Human Cortical Bone Free Water at 1.5T
A Akbari, Shahrokh Abbasi Rad, Hamidreza Saligheh Rad .
Large pores of human cortical bone (N30 μm) are filled with fluids, essentially consisting of water, suggesting that cortical bone free water can be considered as a reliable surrogate measure of cortical bone porosity and hence quality. Signal from such pores can be reliably captured using Short Echo Time (STE) pulse sequence with echo-time in the range of 1–1.5 msec (which should be judiciously selected correspond to T2 value of free water molecules). Furthermore, it is well-known that cortical bone T1-relaxivity is a function of its geometry, suggesting that cortical bone free water increases with age. In this work, we quantified cortical bone free water longitudinal relaxation time (T1) by a Dual-TR technique using STE pulse sequence. In the sequel, we investigated relationship between STE-derived cortical bone free water T1-values and age in a group of healthy volunteers (thirty subjects covering the age range of 20–70 years) at 1.5 T. Preliminary results showed that cortical bone free water T1 highly correlates with age (r2 = 0.73, p b 0.0001), representing cortical bone free water T1 as a reliable indicator of cortical bone porosity and age-related deterioration. It can be concluded that STE-MRI can be utilized as proper alternative in quantifying cortical bone porosity parameters in-vivo, with the advantages of widespread clinical availability and being cost-effective.
Relaxometry, Cortical bone, Porosity, Bone water, T1 quantification .