title: Modeling of T2* decay in vertebral bone marrow fat quantification.
abstract: Bone marrow fat fraction mapping using chemical shift encoding-based water-fat separation is becoming a useful tool in investigating the association between bone marrow adiposity and bone health and in assessing cancer treatment-induced bone marrow damage. Vertebral bone marrow is characterized by short T2* relaxation times, which are in general different for the water and fat components and can confound fat quantification. The purpose of the present study is to compare different approaches to T2* correction in chemical shift encoding-based water-fat imaging of vertebral bone marrow using single-voxel MRS as reference. Eight-echo gradient-echo imaging and single-voxel MRS measurements were made on the spine (L3-L5) of 25 healthy volunteers. Different approaches were evaluated for correction of T2* effects: (a) single-T2* correction, (b) dual-T2* correction, (c) T2' correction using the a priori-known T2 from the MRS at each vertebral body and (d) T2' correction using the a priori-known T2 equal to previously measured average values. Dual-T2* correction resulted in noisier imaging fat fraction maps than single-T2* correction or T2' correction using a priori-known T2. Linear regression analysis between imaging and MRS fat fraction showed a slope significantly different from 1 when using single-T2* correction (R(2) = 0.96) or dual-T2* correction (R(2) = 0.87). T2' correction using the a priori-known T2 resulted in a slope not significantly different from 1, an intercept significantly different from 0 (between 2.4% and 3%) and R(2) = 0.96. Therefore, a T2' correction using a priori-known T2 can remove the fat fraction bias induced by the difference in T2* between water and fat components without degrading noise performance in fat fraction mapping of vertebral bone marrow.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany.
authors.forename: Dimitrios C
authors.initials: DC
authors.lastname: Karampinos
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Ruschke
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Dieckmeyer
authors.affiliation: Philips Research Laboratory, Hamburg, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Eggers
authors.affiliation: Philips Healthcare, Hamburg, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Kooijman
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany.
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Rummeny
authors.affiliation: Section of Neuroradiology, Technische Universität München, Munich, Germany.
authors.forename: Jan S
authors.initials: JS
authors.lastname: Bauer
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Baum
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology / Q000502:physiology*; D050154:Adiposity / Q000502:physiology*; D000328:Adult; D001853:Bone Marrow / Q000033:anatomy & histology / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: MRI; MRS; fat quantification; spine; vertebral bone marrow; water-fat separation