k-Space Water-Fat Decomposition With T-2* Estimation and Multifrequency Fat Spectrum Modeling for Ultrashort Echo Time Imaging

Purpose: To demonstrate the feasibility of combining a chemical shift-based water-fat separation method (IDEAL) with a 2D ultrashort echo time (UTE) sequence for imaging and quantification of the short T-2 tissues with robust fat suppression. Materials and Methods: A 2D multislice UTE data acquisition scheme was combined with IDEAL processing, including T-2* estimation, chemical shift artifacts correction, and multifrequency modeling of the fat spectrum to image short T-2 tissues such as the Achilles tendon and meniscus both in vitro and in vivo. The integration of an advanced field map estimation technique into this combined method, such as region growing (RG), is also investigated. Results: The combination of IDEAL with UTE imaging is feasible and excellent water-fat separation can be achieved for the Achilles tendon and meniscus with simultaneous T-2* estimation and chemical shift artifact correction. Multifrequency modeling of the fat spectrum yields more complete water-fat separation with more accurate correction for chemical shift artifacts. The RG scheme helps to avoid water-fat swapping. Conclusion: The combination of UTE data acquisition with IDEAL has potential applications in imaging and quantifying short T-2 tissues, eliminating the necessity for fat suppression pulses that may directly suppress the short T-2 signals.