Abstract
ObjectiveTo determine the image quality of fast spin echo (FSE) with mDixon relative to spectral attenuated inversion recovery (SPAIR) FSE sequences in musculoskeletal tumor imaging on a 1.5-T MRI system.Materials and methodsIn a HIPAA-compliant prospective study, 265 patients requiring musculoskeletal tumor MRI scans were included. Patient consent was waived by the medical ethical committee. Two radiologists compared SPAIR and mDixon FSE water-only images in both T2- and T1-weighted gadolinium-enhanced (T1-Gd) sequences using a five-point scale (paired samples t test and visual grading characteristics curves (VGC)). Homogeneity of fat suppression, noise, contrast, several artifacts (motion, phase, edge blurring and water–fat swap) and subjective preference were evaluated.ResultsReaders did not have subjective preference for either sequence in 71% and 55% (reader 1 and 2, respectively). Scores for homogeneous fat suppression were significantly (p < 0.01) higher for mDixon (4.88 in T2 and 4.87 in T1-Gd) than for SPAIR (4.31 for T2 and 4.21 for T1-Gd). All VGC curves for homogeneity demonstrated preference for mDixon. In 57 individual mDixon cases, fat-suppression homogeneity was strikingly better (≥ 2 points higher), namely in areas with field heterogeneity. Average noise and contrast scores were slightly higher for mDixon, as were motion artifact scores for SPAIR (< 0.5 points difference).ConclusionsmDixon fat suppression was significantly more homogeneous than SPAIR on both T2 and T1-Gd FSE images in musculoskeletal tumor protocols. In areas of field inhomogeneity, mDixon outperforms SPAIR. SPAIR had slightly less motion artifacts than mDixon.
Highlights
Fat suppression in musculoskeletal oncology magnetic resonance imaging (MRI) is used for improving lesion conspicuity and lesion characterization
Since the introduction of turbo or fast spin echo sequences (FSE), fat suppression has become indispensable because decreased J-coupling causes high signal intensity of fat in these sequences [1]
During the first year (129 patients), a T1-weighted gadolinium-enhanced (T1-Gd) modified Dixon (mDixon) sequence was added to the standard protocol
Summary
Fat suppression in musculoskeletal oncology magnetic resonance imaging (MRI) is used for improving lesion conspicuity and lesion characterization. Several methods of fat suppression have been developed and implemented over the years, each with their own advantages and limitations. These techniques are often based on chemical shift, non-selective inversion pulses, and hybrid techniques. In the 1980s, Dixon introduced a chemical shift method based on phase shift secondary to water–fat resonance frequency differences. The method allowed the separation of water and fat signals to be postponed to the image postprocessing phase, and required only a single data acquisition sequence with multiple echo times [2]. Relative to other fatsuppression techniques, the classic Dixon techniques have long acquisition times and high sensitivity to B0 heterogeneity.
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