title: MRI quantification of diffusion and perfusion in bone marrow by intravoxel incoherent motion (IVIM) and non-negative least square (NNLS) analysis.
abstract: OBJECTIVE
  To assess the feasibility of measuring diffusion and perfusion fraction in vertebral bone marrow using the intravoxel incoherent motion (IVIM) approach and to compare two fitting methods, i.e., the non-negative least squares (NNLS) algorithm and the more commonly used Levenberg-Marquardt (LM) non-linear least squares algorithm, for the analysis of IVIM data.
  
  
  METHODS
  MRI experiments were performed on fifteen healthy volunteers, with a diffusion-weighted echo-planar imaging (EPI) sequence at five different b-values (0, 50, 100, 200, 600 s/mm2), in combination with an STIR module to suppress the lipid signal. Diffusion signal decays in the first lumbar vertebra (L1) were fitted to a bi-exponential function using the LM algorithm and further analyzed with the NNLS algorithm to calculate the values of the apparent diffusion coefficient (ADC), pseudo-diffusion coefficient (D*) and perfusion fraction.
  
  
  RESULTS
  The NNLS analysis revealed two diffusion components only in seven out of fifteen volunteers, with ADC=0.60±0.09 (10(-3) mm(2)/s), D*=28±9 (10(-3) mm2/s) and perfusion fraction=14%±6%. The values obtained by the LM bi-exponential fit were: ADC=0.45±0.27 (10(-3) mm2/s), D*=63±145 (10(-3) mm2/s) and perfusion fraction=27%±17%. Furthermore, the LM algorithm yielded values of perfusion fraction in cases where the decay was not bi-exponential, as assessed by NNLS analysis.
  
  
  CONCLUSIONS
  The IVIM approach allows for measuring diffusion and perfusion fraction in vertebral bone marrow; its reliability can be improved by using the NNLS, which identifies the diffusion decays that display a bi-exponential behavior.
authors.affiliation: Department of Imaging, Rennes University Hospital, Rennes, France.
authors.forename: A J
authors.initials: AJ
authors.lastname: Marchand
authors.affiliation: INSERM, UMR 1099, Rennes F-35000, France; Université de Rennes 1, LTSI, Rennes F-35000, France.
authors.forename: E
authors.initials: E
authors.lastname: Hitti
authors.affiliation: INSERM, UMR 1099, Rennes F-35000, France; Université de Rennes 1, LTSI, Rennes F-35000, France.
authors.forename: F
authors.initials: F
authors.lastname: Monge
authors.affiliation: INSERM, UMR 1099, Rennes F-35000, France; Université de Rennes 1, LTSI, Rennes F-35000, France; CRLCC, Centre Eugène Marquis, Rennes F-35000, France.
authors.forename: H
authors.initials: H
authors.lastname: Saint-Jalmes
authors.affiliation: Department of Imaging, Rennes University Hospital, Rennes, France.
authors.forename: R
authors.initials: R
authors.lastname: Guillin
authors.affiliation: Department of Imaging, Rennes University Hospital, Rennes, France.
authors.forename: R
authors.initials: R
authors.lastname: Duvauferrier
authors.affiliation: INSERM, UMR 1099, Rennes F-35000, France; Université de Rennes 1, LTSI, Rennes F-35000, France. Electronic address: gambarota@gmail.com.
authors.forename: G
authors.initials: G
authors.lastname: Gambarota
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001853:Bone Marrow / Q000033:anatomy & histology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016018:Least-Squares Analysis; D008297:Male; D015203:Reproducibility of Results; D013131:Spine; D055815:Young Adult
keywords: Bone marrow; Diffusion; IVIM; Intravoxel incoherent motion; NNLS; Perfusion