Purpose: To propose the combined modified-Dixon and PROPELLER sequence with low refocusing flip angle (RFA) and investigate whether this sequence can acquire clinical contrast-enhanced (CE), fat-suppressed T1-weighted (T1W) images of the head and neck.
Methods: The optimal RFA for T1W imaging was investigated in the brain of a healthy volunteer. The motion artifacts, water-fat separation error, contrast ratio (CR), and comprehensive quality were evaluated through comparison with a standard Cartesian modified-Dixon sequence in 50 patients. Two radiologists independently scored motion artifacts and water-fat separation error using a 4-point scale (1, unacceptable; 4, excellent) and comprehensive quality using a 5-point scale (1, substantially inferior; 5, substantially superior). The CR between CE lesions and non-CE muscle was calculated.
Results: The optimal RFA of 40° was determined. In the motion artifact assessment, ratings of 3 or 4 points were assigned to 83% (observer-1, 42/50; observer-2, 41/50) and 99% (50/50; 49/50) of cases for the standard and proposed sequences, respectively (p < 0.001; p < 0.001). For the water-fat separation error assessment, ratings of 3 or 4 points were assigned to 100% (50/50; 50/50) and 97% (48/50; 49/50) of cases, respectively (p < 0.001; p = 0.02). In comprehensive evaluation, the proposed sequence was equal, slightly superior, or substantially superior to the standard sequence in 85% (39/50; 46/50). The CR was significantly higher with the proposed sequence [2.27 (1.99-2.97) vs. 2.08 (1.88-2.42), p < 0.001].
Conclusion: The proposed sequence acquired stable fat-suppressed CE T1W images without motion artifacts and yielded superior overall image quality compared with the standard sequence.
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