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E1103. Body Dixon Imaging: Pearls and Pitfalls
Authors
  1. Reza Salari; Mallinckrodt Institute of Radiology
  2. Anup Shetty; Mallinckrodt Institute of Radiology
  3. Mark Hoegger; Mallinckrodt Institute of Radiology
  4. Daniel Young; Mallinckrodt Institute of Radiology
Background
The Dixon method is a powerful body MR diagnostic tool, but many radiologists are unfamiliar with this valuable technique. Described in the 1980s by W. Thomas Dixon, this method generates fat- and water-only sequences via voxel intensity differences between in- and opposed-phase MR images [1, 2]. Water- and fat-only sequences can better reveal lesions and characterize their composition. Modern MR scanners can leverage the Dixon method water-only sequences for superior fat suppression. Compared to traditional frequency-selective fat suppression, Dixon water-only sequences are less sensitive to magnetic field inhomogeneities and provide more uniform fat suppression [2, 3]. The purpose of this exhibit is to review the Dixon method’s physics, artifacts, limitations, and protocol design and demonstrate its value in body MR.

Educational Goals / Teaching Points
This exhibit will describe the fundamental physics of the Dixon method. Dixon method-generated water-only reconstructions will be compared to other fat suppression methods. The value of the Dixon method for characterizing fat-containing and fat-absent lesions in the torso will be illustrated using a case-based approach. The relationship of in- and opposed-phase sequences to Dixon method fat-only and water-only sequences will be reviewed. Effective use of Dixon imaging with attention to artifacts, sequence parameters, and protocol construction will be highlighted. After reviewing the exhibit, the reader should be able to use Dixon imaging in their practice.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Practical considerations such as more robust and uniform fat suppression, fat/water swap artifacts, longer TRs, and breath-holding will be discussed. Case-based examples will highlight the Dixon method’s utility for identifying metastatic lesions and characterizing fat-containing lesions in the bone, liver, adrenal glands, kidneys, and other soft tissues.

Conclusion
The Dixon method generates fat-only and water-only images using data from in-phase and opposed-phase acquisitions. A basic understanding of this powerful technique, and its pearls and pitfalls, can aid the body MR imager in lesion detection and characterization.