Two‐point dixon method with flexible echo times

Abstract

The two-point Dixon method is a proton chemical shift imaging technique that produces separated water-only and fat-only images from a dual-echo acquisition. It is shown how this can be achieved without the usual constraints on the echo times. A signal model considering spectral broadening of the fat peak is proposed for improved water/fat separation. Phase errors, mostly due to static field inhomogeneity, must be removed prior to least-squares estimation of water and fat. To resolve ambiguity of the phase errors, a corresponding global optimization problem is formulated and solved using a message-passing algorithm. It is shown that the noise in the water and fat estimates matches the Cramér-Rao bounds, and feasibility is demonstrated for in vivo abdominal breath-hold imaging. The water-only images were found to offer superior fat suppression compared with conventional spectrally fat suppressed images. Magn Reson Med 65:994-1004, 2011.

Comparison between modified Dixon MRI techniques, MR spectroscopic relaxometry, and different histologic quantification methods in the assessment of hepatic steatosis

“…In recent years, several techniques of quantitative magnetic resonance imaging (qMRI) have been introduced for fast acquisition of quantitative proton density fat fraction (PDFF) maps covering large parts of the liver or the entire organ [17][18][19][20][21]. Based on the original method exploiting the periodic MR signal cancelation and addition during spin precession in water and lipids, modified Dixon techniques (mDixon) permit flexible echo times (TE) not restricted to exact in-phase/opposed-phase values.…”

“…Based on the original method exploiting the periodic MR signal cancelation and addition during spin precession in water and lipids, modified Dixon techniques (mDixon) permit flexible echo times (TE) not restricted to exact in-phase/opposed-phase values. Thus, dual-echo mDixon (2E-mDixon) techniques are also used for fast and high resolution fat suppressed imaging [17,18,22]. Besides inclusion of a multipeak spectral model with several lipid components, mDixon can be extended to a multi-echo variant, e.g.…”

Correction of Fat-Water Swaps in Dixon MRI

“…There are several extensions [8] and alternatives to the original IDEAL method, including graph-cut formulations [7] and other discrete optimization approaches [9,10]. All require access to the original echo sequences or a B0 field map [11] as part of their optimization procedure.…”

Fast triple-spin-echo Dixon (FTSED) sequence for water and fat imaging

“…Dixon methods can be classified as single-point (SPD or 1PD) [18], two-point (2PD) [19,20,21,22,23,24,25], three-point (3PD) [26,27,28] and multipoint (MPD) [29,30,31,32,33]. The various implementations attempt to overcome several common problems of all Dixon methods.…”