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Separation of collagen‐bound and porous bone‐water longitudinal relaxation in mice using a segmented inversion recovery zero‐echo‐time sequence
Author(s) -
Marcon Magda,
Keller Daniel,
Wurnig Moritz C.,
Weiger Markus,
Kenkel David,
Eberhardt Christian,
Eberli Daniel,
Boss Andreas
Publication year - 2017
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26277
Subject(s) - exponential function , cortical bone , exponential decay , nuclear magnetic resonance , in vivo , relaxation (psychology) , materials science , biomedical engineering , nuclear medicine , chemistry , physics , mathematics , anatomy , mathematical analysis , medicine , nuclear physics , biology , microbiology and biotechnology
Purpose Cortical bone mechanical properties are related to the collagen‐bound water (CBW) and pore water (PW) components of cortical bone. The study evaluates the feasibility of zero‐echo‐time imaging in mice in vivo for longitudinal relaxation time (T1) measurements in cortical bone and separation of CBW and PW components. Methods Zero‐echo‐time data were acquired at 4.7 Tesla in six mice with 14 different inversion times (0–2,600 ms). Region‐of‐interest analysis was performed at level of femur diaphysis. The T1 of cortical bone and of CBW (T1cbw) and PW (T1pw) as well as the CBW fraction (cbwf) was computed using a mono‐exponential and a bi‐exponential fitting approach, respectively. The sum of the squared residuals (Res) to the fit was provided for both approaches. Results For the mono‐exponential model, mean T1 ± standard deviation (SD) was 1,057 ± 160 ms. The bi‐exponential approach provided a reliable separation of two different bone‐water components, with a mean T1cbw of 213 ± 95 ms, T1pw of 2,152 ± 894 ms, and cbwf of 7.4 ± 2.7 %. Lower Res was obtained with bi‐exponential approach ( P < 0.001), and Res mean values ± SD were 0.016 ± 0.007 (bi‐exponential) and 0.033 ± 0.016 (mono‐exponential). Conclusion Zero‐echo‐time imaging allows for longitudinal relaxation measurements of cortical bone in vivo in mice models, with a reliable separation of PW and CBW components using a bi‐exponential curve fitting approach. Magn Reson Med 77:1909–1915, 2017. © 2016 International Society for Magnetic Resonance in Medicine