Magnetic Resonance Engineering Laboratory, Ming Hsieh Department of Electrical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA.
Obesity (Silver Spring). 2010 Apr;18(4):841-7. doi: 10.1038/oby.2009.352. Epub 2009 Oct 15.
The ability to accurately and noninvasively quantify fatty infiltration in organs such as the liver and the pancreas remains a critical component in understanding the link between obesity and its comorbidities such as type 2 diabetes and fatty liver disease. Single-voxel ((1)H) proton magnetic resonance spectroscopy (MRS) has long been regarded as the gold-standard noninvasive technique for such measurements. Recent advances in three-dimensional fat-water magnetic resonance imaging (MRI) methods have led to the development of rapid, robust, and quantitative approaches that can accurately characterize the proportion of fat and water content in underlying tissues across the full imaging volume, and hence entire organs of interest. One such technique is called IDEAL (Iterative Decomposition with Echo Asymmetry and Least squares estimation). This article prospectively compares three-dimensional (3D) IDEAL-MRI and single-voxel MRS in the assessment of hepatic (HFF) and pancreatic fat fraction (PFF) in 16 healthy subjects. MRS acquisitions took 3-4 min to complete whereas IDEAL acquisitions were completed in 20-s breath-holds. In the liver, there was a strong correlation (slope = 0.90, r(2) = 0.95, P < 0.001) between IDEAL and MRS-based fat fractions. In the pancreas, a poorer agreement between IDEAL and MRS was observed (slope = 0.32, r(2) = 0.51, P < 0.02). The discrepancy of PFF is likely explained by MRS signal contamination from surrounding visceral fat, presumably during respiratory motion. We conclude that IDEAL is equally accurate in characterizing hepatic fat content as MRS, and is potentially better suited for fat quantification in smaller organs such as the pancreas.
准确且无创地定量评估肝脏和胰腺等器官的脂肪浸润能力，是理解肥胖及其合并症（如 2 型糖尿病和脂肪肝疾病）之间关联的关键组成部分。单体素 (1)H 质子磁共振波谱 (MRS) 一直以来被视为此类测量的金标准无创技术。近年来，三维水脂磁共振成像 (MRI) 方法的进步，催生了快速、稳健且定量的方法，这些方法可以准确地描述整个成像容积内（进而整个感兴趣器官）的脂肪和水含量比例。其中一种技术被称为 IDEAL（带回波不对称和最小二乘估计的迭代分解）。本文前瞻性地比较了三维 (3D) IDEAL-MRI 和单体素 MRS 技术，以评估 16 位健康受试者的肝脏 (HFF) 和胰腺脂肪分数 (PFF)。MRS 采集耗时 3-4 分钟，而 IDEAL 采集耗时 20 秒屏气。在肝脏中，IDEAL 和基于 MRS 的脂肪分数之间存在很强的相关性（斜率 = 0.90，r² = 0.95，P < 0.001）。在胰腺中，IDEAL 和 MRS 之间的一致性较差（斜率 = 0.32，r² = 0.51，P < 0.02）。PFF 的差异可能是由于呼吸运动期间周围内脏脂肪对 MRS 信号的污染所致。我们的结论是，IDEAL 同样准确地描述了肝脏的脂肪含量，并且可能更适合于胰腺等较小器官的脂肪定量。
