Peng Qi, McColl Roderick W, Wang Jihong, Chia Jonathan M, Weatherall Paul T
Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9085, USA.
J Magn Reson Imaging. 2005 Mar;21(3):263-71. doi: 10.1002/jmri.20252.
To compare the performance of a novel water-saturated b-SSFP sequence with that of a conventional T1-weighted turbo spin echo (T1W TSE) sequence for abdominal fat quantification.
A water-saturated, segmented, three-dimensional balanced steady-state free precession (b-SSFP) sequence and a traditional T1W TSE sequence were both employed on phantom and human studies. For phantom studies, a dual-layered phantom with known internal/external oil volumes was imaged using the two sequences. Images obtained by the two sequences were both processed using a computer-aided semiautomatic program for oil volume quantification. For human studies, six volunteers were scanned axially, centered at L2-L3 levels. Signal-to-noise ratio (SNR)(fat), contrast-to-noise ratio (CNR)(fat-muscle), CNR(fat-large bowel), and CNR(fat-small bowel) were calculated on hand-drawn regions of interest (ROIs), and averaged over all six slices for each subject. Statistical analyses were then performed to determine the SNR and CNR differences between images obtained by the two techniques.
The phantom studies show that water-saturated b-SSFP offers a significantly closer estimation of true oil volumes compared with that of T1W TSE (P < 0.0001), as well as a more accurate internal/external volume ratio (P = 0.0001). In human studies, three-dimensional water-saturated b-SSFP images demonstrated higher CNR than that of T1W TSE (P < 0.0005), and very close SNR(fat) (P = 0.045).
The proposed three-dimensional water-saturated b-SSFP sequence can generate high quality fat-only abdominal images with high CNR and SNR in shorter scan duration than the conventional T1W TSE approach. As images generated by this sequence suffer from no flow artifacts, and are less sensitive to bulk, respiratory, and bowel motion, three-dimensional water-saturated b-SSFP is a faster and more robust method for improving abdominal fat quantification using MRI.
比较一种新型水饱和b-SSFP序列与传统T1加权涡轮自旋回波（T1W TSE）序列在腹部脂肪定量方面的性能。
在体模和人体研究中均采用了水饱和、分段、三维平衡稳态自由进动（b-SSFP）序列和传统的T1W TSE序列。对于体模研究，使用这两种序列对具有已知内部/外部油体积的双层体模进行成像。由这两种序列获得的图像均使用计算机辅助半自动程序进行处理以进行油体积定量。对于人体研究，对六名志愿者在L2-L3水平中心进行轴向扫描。在手绘感兴趣区域（ROI）上计算信噪比（SNR）（脂肪）、对比噪声比（CNR）（脂肪-肌肉）、CNR（脂肪-大肠）和CNR（脂肪-小肠），并对每个受试者的所有六个切片求平均值。然后进行统计分析以确定两种技术获得的图像之间的SNR和CNR差异。
体模研究表明，与T1W TSE相比，水饱和b-SSFP对真实油体积的估计明显更接近（P < 0.0001），并且内部/外部体积比更准确（P = 0.00）。在人体研究中，三维水饱和b-SSFP图像显示出比T1W TSE更高的CNR（P < 0.0005），并且SNR（脂肪）非常接近（P = 0.045）。
所提出的三维水饱和b-SSFP序列能够在比传统T1W TSE方法更短的扫描时间内生成具有高CNR和SNR的高质量仅含脂肪的腹部图像。由于该序列生成的图像不存在流动伪影，并对整体、呼吸和肠道运动不太敏感，三维水饱和b-SSFP是一种使用MRI改善腹部脂肪定量的更快、更稳健的方法。
