title: Quantitative in vivo diffusion imaging of cartilage using double echo steady-state free precession.
abstract: Single-shot echo-planar imaging techniques are commonly used for diffusion-weighted imaging (DWI) but offer rather poor spatial resolution and field-of-view coverage for species with short T(2) . In contrast, steady-state free precession (SSFP) has shown promising results for DWI of the musculoskeletal system, but quantification is generally hampered by its prominent sensitivity on relaxation times. In this work, a new and truly diffusion-weighted (that is relaxation time independent) SSFP DWI technique is introduced using a double-echo steady-state approach. Within this framework (and this is in contrast to common SSFP DWI techniques using SSFP-Echo) both primary echo paths of nonbalanced SSFP are acquired, namely the FID and the Echo. Simulations and in vitro measurements reveal that the ratio of the Echo/FID signal ratios of two double-echo steady-state scans acquired with and without diffusion sensitizing dephasing moments provides a highly relaxation independent quantity for diffusion quantification. As a result, relaxation-independent high-resolution (0.4 × 0.4 - 0.6 × 0.6 mm(2) in-plane resolution) quantitative in vivo SSFP DWI is demonstrated for human articular cartilage using diffusion-weighted double-echo steady-state scans in the knee and ankle joint at 3.0 T. The derived diffusion coefficients for cartilage (D ∼ 1.0-1.5 μm(2) /ms) and synovial fluid (D ∼ 2.6 μm(2) /ms) are in agreement with previous work.
authors.affiliation: Division of Radiological Physics, Department of Medical Radiology, University of Basel Hospital, Basel, Switzerland. oliver.bieri@unibas.ch
authors.forename: Oliver
authors.initials: O
authors.lastname: Bieri
authors.forename: Carl
authors.initials: C
authors.lastname: Ganter
authors.forename: Klaus
authors.initials: K
authors.lastname: Scheffler
mesh_terms: D000465:Algorithms; D002358:Cartilage, Articular / Q000033:anatomy & histology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007719:Knee Joint / Q000033:anatomy & histology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity