http://www.nitrc.org/forum/forum.php?forum_id=7139 <table border="0" width="100%"><tr><td align="left"/></tr></table> <p><b>An efficient reconstruction algorithm based on the alternating direction method of multipliers for joint estimation of R2* and off-resonance in fMRI.</b></p> <p>IEEE Trans Med Imaging. 2017 Feb 13;:</p> <p>Authors: Hu C, Reeves S, Peters D, Twieg D</p> <p>Abstract<br/> R 2 mapping is a useful tool in blood-oxygen-level dependent (BOLD) fMRI due to its quantitative nature. However, like T 2 -weighted imaging, standard R 2 mapping based on multiecho EPI suffers from geometric distortion, due to strong offresonance near the air-tissue interface. Joint mapping of R 2 and off-resonance can correct the geometric distortion and is less susceptible to motion artifacts. Single-shot joint mapping of R 2 and off-resonance is possible with a rosette trajectory due to its frequent sampling of the k-space center. However, the corresponding reconstruction is nonlinear, ill-conditioned, largescale, and computationally inefficient with current algorithms. In this work, we propose a novel algorithm for joint mapping of R 2 and off-resonance, using rosette k-space trajectories. The new algorithm, based on the alternating direction method of multipliers (ADMM), improves the reconstruction efficiency by simplifying the original complicated cost function into a composition of simpler optimization steps. Compared to a recently developed trust region algorithm, the new algorithm achieves the same accuracy and an acceleration of 3-6 fold in reconstruction time. Based on the new algorithm, we present simulation and in vivo data from single-shot, double-shot, and quadruple-shot rosettes and demonstrate the improved image quality and reduction of distortions in the reconstructed R 2 map.<br/> </p><p>PMID: 28207389 [PubMed - as supplied by publisher]</p> en-us Copyright 2000-2026 NITRC OSI Wed, 06 May 2026 10:13:06 GMT http://blogs.law.harvard.edu/tech/rss NITRC RSS generator