FSE T2-weighted two-point Dixon technique for fat suppression in the lumbar spine: comparison with SPAIR technique

Abstract

PURPOSEFat suppression magnetic resonance imaging (MRI) technique has been used to improve the diagnostic confidence in lumbar spine diseases. We aimed to compare T2-weighted water-fat separation technique (T2 Dixon) with spectral attenuated inversion recovery (SPAIR) image for fat suppression. METHODSLumbar spine MRI examinations were performed in 79 patients by using a 3.0 T machine. We compared T2 Dixon water-only image and SPAIR image for the evaluation of fat suppression quality and lesion conspicuity. For qualitative evaluation, two radiologists scored the images from Dixon and SPAIR for fat suppression uniformity and lesion conspicuity. Quantitative assessment was also performed for 39 lesions in 26 patients who had lesions in their spine bodies. Contrast ratio (CR) and contrast-to-noise ratio (CNR) were calculated by signal intensity measurement of the lesions, adjacent bodies, and background noise. The Wilcoxon's signed-rank test and paired sample t-test were used to assess the statistical significance of qualitative and quantitative data, respectively. RESULTSFor qualitative assessment, T2 Dixon water-only image showed higher mean scores for fat suppression quality and lesion conspicuity than SPAIR (2.99±0.11 vs. 2.18±0.38 and 2.84±0.37 vs. 2.28±0.51, respectively). For quantitative measurement, the CR and CNR values of the lesions were higher on T2 Dixon than on SPAIR. Both qualitative and quantitative results showed statistically significant differences between T2 Dixon and SPAIR (P < 0.01 in all). (1-3). However, the train of 180° rephasing pulses in FSE and short T1 relaxation time of fat affect J-coupling modulation, which produces bright signal of the fat on T2-weighted image (4). Increased signal of the fat on T2-weighted image can obscure underlying pathology with elongated T2 signal such as edema, bone marrow infiltration, and metastasis (5). Thus, additional T2-weighted image with fat suppression is necessary to improve visualization of abnormalities in an anatomical region with abundant fat component such as the lumbar spine. CONCLUSIONSeveral fat suppression techniques have been developed and widely used: chemical shift-selective saturation (CHESS), short-tau inversion recovery (STIR) and spectral attenuated inversion recovery (SPAIR) (6-8). The CHESS and STIR have advantages and disadvantages. Although CHESS has advantages of selectivity for fat and high signal-to-noise ratio (SNR), it is vulnerable to magnetic field inhomogeneity. STIR is insensitive to magnetic field inhomogeneity; however, it is not specific for fat. SPAIR is a hybrid technique combining the fat selectivity of CHESS and the inversion radiofrequency pulse of STIR. Thus, it has advantages of high fat selectivity and low vulnerability to the magnetic field inhomogeneity (7, 9).

Occult Disco-Ligamentous Lesions of the Subaxial c-Spine—A Comparison of Preoperative Imaging Findings and Intraoperative Site Inspection

“…Acquiring T2-weighted DIXON sequences may allow to skip dedicated T1-weighted, T2-weighted, and STIR sequences, saving scan time and limiting the duration of time inside the scanner for trauma patients, which could limit motion artifacts related to long acquisition times. Furthermore, simultaneous to such time savings, the DIXON method could generate images with an elevated signal-to-noise ratio compared to STIR imaging and more homogeneous fat suppression [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. These advancements may increase the diagnostic yield of preoperative MRI in suspected disco-ligamentous injury; however, due to the novelty of the approach on commercially available and clinically used MRI systems, data for comparison to standard protocols is currently mostly lacking in trauma patients.…”

Inter-observer variations of the tumor bed delineation for patients after breast conserving surgery in preoperative magnetic resonance and computed tomography scan fusion

“…T2-SPAIR is a technique combining the fat selectivity of chemical shift-selective saturation and the inversion radiofrequency pulse of short-tau inversion recovery [16].…”

Implementation of a sagittal T2-weighted DIXON turbo spin-echo sequence may shorten MRI acquisitions in the emergency setting of suspected spinal bleeding

“…In a study among patients showing various types of vertebral lesions (including recent fractures, spondylitis, metastasis, and haemangioma), a T2-weighted DIXON sequence showed more homogeneous fat suppression and superior lesion conspicuity when compared to imaging using spectral attenuated inversion recovery (SPAIR) [ 17 ]. For the degenerative lumbar spine, previous studies were able to demonstrate that imaging with a single sagittal T2-weighted DIXON sequence could replace the combination of dedicated T1-weighted, T2-weighted, and STIR sequences, which would not be at the expense of worsened diagnostic performance [ 18 , 19 ].…”

“…For the detection of bone metastases along the spine, it has recently been demonstrated that fat and water images derived from a T2-weighted DIXON sequence provide diagnostic performance similar to a protocol including standard T1-weighted sequences; thus, the fat images of the T2-weighted DIXON sequence might probably replace conventional T1weighted imaging [15,16]. In a study among patients showing various types of vertebral lesions (including recent fractures, spondylitis, metastasis, and haemangioma), a T2-weighted DIXON sequence showed more homogeneous fat suppression and superior lesion conspicuity when compared to imaging using spectral attenuated inversion recovery (SPAI R) [17]. For the degenerative lumbar spine, previous studies were able to demonstrate that imaging with a single sagittal T2-weighted DIXON sequence could replace the combination of dedicated T1-weighted, T2weighted, and STIR sequences, which would not be at the expense of worsened diagnostic performance [18,19].…”