Original contributions A fast spin echo two-point Dixon technique and its combination with sensitivity encoding for efficient T2-weighted imaging B Jingfei Ma a, 4 , Jong Bum Son a,b , James A. Bankson a , R. Jason Stafford a , Haesun Choi c , Dustin Ragan a a Department of Imaging Physics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030-4009, USA b Department of Electrical Engineering, Texas A&M University, College Station, TX 77840, USA c Department of Diagnostic Radiology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030-4009, USA Received 30 June 2005; revised 16 October 2005; accepted 16 October 2005 Abstract A fast spin echo two-point Dixon (fast 2PD) technique was developed for efficient T2-weighted imaging with uniform water and fat separation. The technique acquires two interleaved fast spin echo images with water and fat in-phase and 1808 out-of-phase, respectively, and generates automatically separate water and fat images for each slice. The image reconstruction algorithm uses an improved and robust region- growing scheme for phase correction and achieves consistency in water and fat identification between different slices by exploiting the intrinsic correlation between the complex images from two neighboring slices. To further lower the acquisition time to that of a regular fast spin echo acquisition with a single signal average, we combined the fast 2PD technique with sensitivity encoding (SENSE). Phantom experiments show that the fast 2PD and SENSE are complementary in scan efficiency and signal-to-noise ratio (SNR). In vivo data from scanning of clinical patients demonstrate that T2-weighted imaging with uniform and consistent fat separation, including breath-hold abdominal examinations, can be readily performed with the fast 2PD technique or its combination with SENSE. D 2005 Elsevier Inc. All rights reserved. Keywords: Two-point Dixon technique; Fast spin echo; SENSE; T2-weighted imaging; Water and fat separation 1. Introduction Suppression of the signal from lipids is essential in many clinical MR imaging applications. Although the chemical shift selective saturation technique (CHESS) [1,2] and the short-tau inversion recovery technique (STIR) [3,4] have been developed and in widespread use for this purpose, both have serious drawbacks. Among them, CHESS is prone to failure in the presence of large magnetic and radiofrequency field inhomogeneities, and is thus subopti- mal in many cases of clinical interest, such as imaging over large fields of view (FOV), at off-isocenter locations, or near interfaces between soft-tissue and body cavities. The STIR technique provides more robust fat suppression in the presence of field inhomogeneities; however, it suffers from a reduced signal-to-noise ratio (SNR) and reduced scan efficiency due to the inclusion of the inversion pulses. Additionally, STIR may adversely affect image contrast, particularly for contrast-enhanced images, because it sup- presses the signal of all tissues with a spin-lattice relaxation time constant (T 1 ) close to that of fat. Multipoint Dixon (MPD) techniques have been shown capable of providing more uniform fat suppression than the CHESS technique in the presence of field inhomogeneities and, unlike the STIR technique, have the additional advantage of maintaining the image contrast, even when contrast agents are injected [5,6]. A major factor preventing the widespread acceptance of the MPD techniques for clinical use, however, is that their acquisition time is typically several times longer than that of a conventional technique with a similar scan protocol. For example, while two-point or even one-point Dixon techniques have been proposed [7–9], most studies on the MPD techniques so far have relied on three-point Dixon (TPD) acquisitions in order to achieve a reasonable image-processing reliability. Using 0730-725X/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.mri.2005.10.005 B Grant support: Bracco Diagnostics/RSNA Research Scholar Grant Award and Goodwin Funds for Targeted Molecular Diagnosis. 4 Corresponding author. E-mail address: jma@di.mdacc.tmc.edu (J. Ma). Magnetic Resonance Imaging 23 (2005) 977 – 982