This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. INTRODUCTION: In order to follow the changes related to early osteoarthritis and cartilage repair, we require the capability to show the morphological and biochemical properties of cartilage. Two promising techniques are T2 mapping and diffusion- weighted imaging (DWI). The Dual-Echo Steady-State (DESS) sequence has been used for morphological imaging and T2 mapping. In this work, we improve the accuracy of T2 measurement using DESS by simultaneously solving for diffusion characteristics (ADC). THEORY: The DESS sequence acquires two echoes per repetition of the RF pulse. The echoes are separated by a spoiler gradient, which provides diffusion sensitivity. The echoes have signal contributions from different pathways and therefore exhibit different diffusion and T2 weightings depending on sequence parameters like flip angle, spoiler gradient area, and timing. While the dependence of the signal on sequence and tissue parameters is complex, two different acquisitions, resulting in four images, can be fitted to the signal equations to estimate T2 and ADC. To read about other projects ongoing at the Lucas Center, please visit http://rsl.stanford.edu/ (Lucas Annual Report and ISMRM 2011 Abstracts)
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