Resolving phase ambiguity in dual‐echo dixon imaging using a projected power method

Abstract

Purpose To develop a fast and robust method to resolve phase ambiguity in dual-echo Dixon imaging. Methods A major challenge in dual-echo Dixon imaging is to estimate the phase error resulting from field inhomogeneity. In this work, a binary quadratic optimization program was formulated to resolve the phase ambiguity. A projected power method was developed to efficiently solve the optimization problem. Both the 1-peak fat model and 6-peak fat model were applied to 3D datasets. Additionally, the proposed method was extended to dynamic MRI applications using the 6-peak fat model. With IRB approval and patient consent/assent, the proposed method was evaluated and compared with region growing on 29 consecutive 3D high-resolution patient datasets. Results Fast and robust water/fat separation was achieved by the proposed method in different representative 3D datasets and dynamic 3D datasets. Superior water/fat separation was achieved using the 6-peak fat model compared with the 1-peak fat model. Compared to region growing, the proposed method reduced water/fat swaps from 76% to 7% of the patient cohort. Conclusion The proposed method can achieve fast and robust phase error estimation in dual-echo Dixon imaging.

Imaging and T2 relaxometry of short‐T2 connective tissues in the knee using ultrashort echo‐time double‐echo steady‐state (UTEDESS)

“…Spoiler gradients (23.5 mT 1 m −1 ms 1 area) were applied on all gradient directions to prevent steady‐state banding, minimally sensitizing the S‐ echoes to diffusion. Water and fat images for both, the S + and S‐ echoes, were generated using a flexible‐echo‐time Dixon water‐fat separation method . The short‐T 2 tissue anatomy was highlighted with a long‐T 2 subtraction where twice the water S‐ image was subtracted from the water S + image .…”

Peripheral nerve magnetic resonance imaging

“…Alternatively, with a slight shifting of the TE to be water and fat in-phase or out-of-phase, two or three of these acquisitions can be used to acquire a water-only image along with a fat-only image, known as Dixon methods 77 , and many variants of this approach exist 78– 80 . The various Dixon methods require knowledge of the B 0 variations to properly separate water from fat signals 81 . The water faction and fat fraction (FF) can be derived from these water-only and fat-only images.…”

Method of B0 mapping with magnitude‐based correction for bipolar two‐point Dixon cardiac MRI

“…It is important to notice that recent advances of the phasor-based approaches (16,28) can potentially reduce the number of fat-water swaps observed in this work when using the phasor-based approach. However, a thorough comparison between these techniques and the B0-NICEbd is out of scope of this work.…”