Comparison of Multi-Echo Dixon Methods with Volume Interpolated Breath-Hold Gradient Echo Magnetic Resonance Imaging in Fat-Signal Fraction Quantification of Paravertebral Muscle

Abstract

ObjectiveTo assess whether multi-echo Dixon magnetic resonance (MR) imaging with simultaneous T2* estimation and correction yields more accurate fat-signal fraction (FF) measurement of the lumbar paravertebral muscles, in comparison with non-T2*-corrected two-echo Dixon or T2*-corrected three-echo Dixon, using the FF measurements from single-voxel MR spectroscopy as the reference standard.Materials and MethodsSixty patients with low back pain underwent MR imaging with a 1.5T scanner. FF mapping images automatically obtained using T2*-corrected Dixon technique with two (non-T2*-corrected), three, and six echoes, were compared with images from single-voxel MR spectroscopy at the paravertebral muscles on levels L4 through L5. FFs were measured directly by two radiologists, who independently drew the region of interest on the mapping images from the three sequences.ResultsA total of 117 spectroscopic measurements were performed either bilaterally (57 of 60 subjects) or unilaterally (3 of 60 subjects). The mean spectroscopic FF was 14.3 ± 11.7% (range, 1.9-63.7%). Interobserver agreement was excellent between the two radiologists. Lin's concordance correlation between the spectroscopic findings and all the imaging-based FFs were statistically significant (p < 0.001). FFs obtained from the T2*-corrected six-echo Dixon sequences showed a significantly better concordance with the spectroscopic data, with its concordance correlation coefficient being 0.99 and 0.98 (p < 0.001), as compared with two- or three-echo methods.ConclusionT2*-corrected six-echo Dixon sequence would be a better option than two- or three-echo methods for noninvasive quantification of lumbar muscle fat quantification.

Measurement of fat content in vertebral marrow using a modified dixon sequence to differentiate benign from malignant processes

“…However, it is well known that there are so many confounding factors in the calculation of fat or water signals by chemical shift‐encoded MRI, including main magnetic field inhomogeneity effects, the presence of multiple peaks in the fat spectrum, effects, T 1 effects, eddy current effects, and the presence of susceptibility‐induced fat resonance shifts . Among them, signal decay is particularly important in the fat quantification of bone marrow because trabecular bone, in general, shortens the of water and fat components, inducing the confounded separation of fat and water signals . The multiple spectral peaks of fat are another large issue in fat quantification using chemical shift‐encoded MRI.…”

“…With recent technical advancements, various chemical shift‐based water–fat separation methods, eg, Dixon methods, have been used to provide the distinctive separation of water and fat by correcting such confounding factors . The FF estimated from these methods is expected to improve the diagnostic performance of chemical shift‐encoded shift MRI in the differentiation of benign from malignant lesions.…”

“…To avoid T 1 saturation, a low excitation flip angle of 3′ was applied. The R2* map is corrected for effects because trabecular bone shortens the of water and fat components inducing a rapid decay of the measured gradient echo signal with TE . A multipeak spectral model with several lipid components was also used in the calculation of the FF map .…”

“…Recently, the Dixon methods with two or more echo times have been applied for the rapid assessment of fat content, which is also called the quantitative water–fat imaging technique or fat fraction MRI . Many Dixon variants have been developed, providing a more consistent separation of fat and water signals by correcting many confounding factors, including the main magnetic field inhomogeneity effects, the presence of multiple peaks in the fat spectrum, effects, T 1 effects, eddy current effects, and the presence of susceptibility‐induced fat resonance shifts . Among them, a modified Dixon (modified Dixon) has been proposed allowing the two echo times at the in‐phase and out‐of‐phase of the water and fat signals to be flexible .…”

Measurement and Compensation of Respiration-Induced B0 Variations in Lumbar Spine Bone Marrow Fat Quantification

“…For both uncompensated and compensated complex images, fat quantification was performed using T2*-IDEAL technique with 6 echoes (8) We used six echoes for both T2* and fat fraction rather than three echoes because previous studies have shown the improved fat fraction estimation when six-echo is applied in GRE-based fat quantification (14)(15)(16). Assuming identical T2* decay for both water and fat, the signal from a voxel including water and fat can be represented as:…”