Robert Adam Horch1,2, Richard Darrell Dortch1,2, Jeffrey S. Nyman3, Daniel Frank Gochberg2,4, Mark. D. Does1,2
1Biomedical Engineering, Vanderbilt University, Nashville, TN, USA; 2Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA; 3Orthopaedics & Rehabilitation, Vanderbilt University, Nashville, TN, USA; 4Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
Human cortical bone contains an array of microanatomical water environments, such as restricted pore spaces, collagen networks, and hydroxyapatite mineral surface hydration zones. As such, in proton NMR measurements cortical bone exhibits a distribution of relaxation times, which are characterized herein by CPMG at 0.5, 4.7, 7, and 9.4 T to examine magnetic field dependencies. Hard and soft inversion-recovery CPMG measurements are also presented, which yield T1-T2 spectra indicative of magnetization transfer among cortical bone relaxation components. At the studied field strengths, cortical bone exhibits a range of T2s from 100us to 500ms, with T1s spanning 20ms to 500ms.