A Primer on Dixon Imaging

Dixon imaging is a technique for separating out water and fat in an MR image that depends on the relative chemical shift between water and fat (as opposed to relying on the absolute resonance frequencies, as in saturation-based techniques). For someone just getting started in this area, or who is simply interested, here is a list of references. I am not attempting to be exhaustive. In particular, I am not focusing strongly on clinical papers or more historical ones.

download: Dixon primer (zipped EndNote library)

• Dixon WT. Simple proton spectroscopic imaging. Radiology 1984;153(1):189-194. PMID 6089263.

As is often the case, reading the original paper is not strictly necessary for a full understanding of either the theory or practice of Dixon imaging. However, this paper does describe in-phase and opposed-phase imaging and gives a good description of the basic idea. Also, it features a fairly entertaining selection of phantoms (an egg, margarine, and dish soap).

• Ma J. Breath-hold water and fat imaging using a dual-echo two-point Dixon technique with an efficient and robust phase-correction algorithm. Magn Reson Med. 2004 Aug;52(2):415-9. PMID 15282827.
• Reeder SB, et al. Multicoil Dixon chemical species separation with an iterative least-squares estimation method. Magn Reson Med. 2004 Jan;51(1):35-45. PMID 14705043.

The two most prolific publishers in Dixon imaging are currently the groups of Jingfei Ma and Scott Reeder. These two papers describe the basic approaches taken by each. Both techniques have been licensed by GE-Healthcare as MEDAL and IDEAL, respectively.

• Xiang QS, An L. Water-fat imaging with direct phase encoding. J Magn Reson Imaging. 1997 Nov-Dec;7(6):1002-15. PMID 9400843.

Although not as prolific, Xiang has also published several articles and his technique is in use at some sites.

The four papers above should prepare you for reading most current research in Dixon imaging. At this point, you may decide you are more interested in reading about the clinical applications of Dixon imaging. This list is particularly non-exhaustive–as a an example, I include no papers about the usefulness of the opposed phase image as a diagnostically useful tool in its own right.

• Ma J, et al. Silicone-specific imaging using an inversion-recovery-prepared fast three-point Dixon technique. J Magn Reson Imaging. 2004 Mar;19(3):298-302. PMID 14994297.
• Ma J, et al. T2-weighted spine imaging with a fast three-point dixon technique: comparison with chemical shift selective fat suppression. J Magn Reson Imaging. 2004 Dec;20(6):1025-9. PMID 15558561.
• Ma J, et al. Fat-suppressed three-dimensional dual echo Dixon technique for contrast agent enhanced MRI. J Magn Reson Imaging. 2004 Dec;20(6):1025-9. PMID 16315212.
• Reeder SB, et al. Cardiac CINE imaging with IDEAL water-fat separation and steady-state free precession. J Magn Reson Imaging. 2005 Jul;22(1):44-52. PMID 15971192.
• Reeder SB, et al. Iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL): application with fast spin-echo imaging. Magn Reson Med. 2005 Sep;54(3):636-44. PMID 16092103.

For a more detailed treatment about the theory and assumptions behind Dixon, the following paper is a must-read:

• Glover GH. Multipoint Dixon technique for water and fat proton and susceptibility imaging. J Magn Reson Imaging. 1991 Sep-Oct;1(5):521-30. PMID 1790376.

These papers give a little more technical development of some of the techniques mentioned:

• An L, Xiang QS. Chemical shift imaging with spectrum modeling. Magn Reson Med. 2001 Jul;46(1):126-30. PMID 11443718.
• Glover GH, Schneider E. Three-point Dixon technique for true water/fat decomposition with B0 inhomogeneity correction. Magn Reson Med. 1991 Apr;18(2):371-83. PMID 2046518.
• Ma J, et al. Method for efficient fast spin echo Dixon imaging. Magn Reson Med. 2002 Dec;48(6):1021-7. PMID 12465112.
• Ma J, et al. A fast spin echo two-point Dixon technique and its combination with sensitivity encoding for efficient T2-weighted imaging. Magn Reson Imaging. 2005 Dec;23(10):977-82. PMID 16376180.
• Pineda AR, et al. Cramer-Rao bounds for three-point decomposition of water and fat. Magn Reson Med. 2005 Sep;54(3):625-35. PMID 16092102.
• Reeder SB, et al. Homodyne reconstruction and IDEAL water-fat decomposition. Magn Reson Med. 2005 Sep;54(3):586-93. PMID 16086311.
• Szumowski J, et al. Phase unwrapping in the three-point Dixon method for fat suppression MR imaging. Radiology. 1994 Aug;192(2):555-61. PMID 8029431.
• Coombs BD, Szumowski J, Coshow W. Two-point Dixon technique for water-fat signal decomposition with B0 inhomogeneity correction. Magn Reson Med. 1997 Dec;38(6):884-9. PMID 9402188.