title: Separation of collagen-bound and porous bone-water longitudinal relaxation in mice using a segmented inversion recovery zero-echo-time sequence.
abstract: 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.
  
  
  
  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.
  
  
  
  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).
  
  
  
  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.
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: Magda
authors.initials: M
authors.lastname: Marcon
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.|Department of Urology, University Hospital Zurich, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Keller
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: Moritz C
authors.initials: MC
authors.lastname: Wurnig
authors.affiliation: Institute for Biomedical Engineering, University of Zurich and Swiss Federal Institute for Technology, Zurich, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Weiger
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Kenkel
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Eberhardt
authors.affiliation: Department of Urology, University Hospital Zurich, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Eberli
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Boss
mesh_terms: D000465:Algorithms; D000818:Animals; D016477:Artifacts; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D003094:Collagen / Q000737:chemistry*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D051379:Mice; D015233:Models, Statistical; D019047:Phantoms, Imaging; D016062:Porosity; D013314:Stress, Mechanical
chemical_list: D003094:Collagen
keywords: cortical bone; longitudinal relaxation; mice; zero-echo-time imaging