title: MRI of bone marrow in the distal radius:  in vivo precision of effective transverse relaxation times.
abstract: The effective transverse relaxation time T2* is influenced by the presence of trabecular bone, and can potentially provide a measure of bone density as well as bone structure. We determined the in vivo precision of T2* in repeated bone marrow measurements. The T2* measurements of the bone marrow of the distal radius were performed twice within 2 weeks in six healthy young volunteers using a modified water-presaturated 3D Gradient-Recalled Acquisition at Steady State (GRASS) sequence with TE 7, 10, 12, 20, and 30; TR 67; flip angle (FA) 90 degrees. An axial volume covering a length of 5.6 cm in the distal radius was measured. Regions of interest (ROIs) were determined manually and consisted of the entire trabecular bone cross-section extending proximally from the radial subchondral endplate. Reproducibility of T2* and area measurements was expressed as the absolute precision error (standard deviation [SD] in ms or mm2) or as the relative precision error (SD/mean x 100, or coefficient of variation [CV] in %) between the two-point measurements. Short-term precision of T2* and area measurements varied depending on section thickness and location of the ROI in the distal radius. Absolute precision errors for T2* times were between 1.3 and 2.9 ms (relative precision errors 3.8-9.5 %) and for area measurements between 20 and 55 mm2 (relative precision errors 5.1-16.4%). This MR technique for quantitative assessment of trabecular bone density showed reasonable reproducibility in vivo and is a promising future tool for the assessment of osteoporosis.
authors.affiliation: Department of Radiology, University of California, San Francisco 94143, USA.
authors.forename: S
authors.initials: S
authors.lastname: Grampp
authors.forename: S
authors.initials: S
authors.lastname: Majumdar
authors.forename: M
authors.initials: M
authors.lastname: Jergas
authors.forename: P
authors.initials: P
authors.lastname: Lang
authors.forename: A
authors.initials: A
authors.lastname: Gies
authors.forename: H K
authors.initials: HK
authors.lastname: Genant
mesh_terms: D000328:Adult; D015519:Bone Density / Q000502:physiology*; D001853:Bone Marrow / Q000033:anatomy & histology; D001856:Bone Marrow Examination; D003720:Densitometry; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D010024:Osteoporosis / Q000175:diagnosis*; D011884:Radius / Q000033:anatomy & histology; D015203:Reproducibility of Results