Lundbom Jesper, Heikkinen Sami, Fielding Barbara, Hakkarainen Antti, Taskinen Marja-Riitta, Lundbom Nina
Department of Medicine, Division of Cardiology, University of Helsinki, 00029 HUS Helsinki, Finland.
J Magn Reson. 2009 Nov;201(1):39-47. doi: 10.1016/j.jmr.2009.07.026. Epub 2009 Aug 3.
This study investigated the impact of fatty acid (FA) composition on the echo time behavior of triglyceride resonances in a clinical setting. The feasibility of (1)H NMR spectroscopy to detect these resonances was also evaluated in human adipose tissue in vivo.
Ten edible oils chosen to cover a wide spectrum of FA compositions were used as phantom material. The detailed FA composition and intrinsic proton spectra of the oils were characterized by gas chromatography and high-resolution (1)H NMR spectroscopy (11.7T), respectively. The detailed echo time behavior of the oils were subsequently measured by (1)H NMR spectroscopy in a clinical scanner (1.5T) using PRESS. The effect of temperature was investigated in five oils.
The olefinic (5.3 ppm) and diallylic (2.8 ppm) resonances exhibited distinct J-modulation patterns independent of oil FA composition. The methylene resonance (1.3 ppm) displayed an exponential decay, with the apparent T(2) showing a weak positive correlation with oil unsaturation (R=0.628, P=0.052), probably a result of changes in viscosity. For the methyl resonance (0.9 ppm), oils high in omega-3 FA displayed a markedly different J-modulation pattern compared to non-omega-3 oils. The characteristic J-modulation of the omega-3 methyl group could be attributed to the phase behavior of the omega-3 methyl triplet signal (all triplet lines in-phase at TE of 135 ms), a result of the omega-3 methyl end forming a first order spin system. The omega-3 methyl outer triplet line at 1.08ppm of the TE=140 ms spectrum was found to be useful for determining the omega-3 content of the oils (R=0.999, standard error of estimate (SE) 0.80). The olefinic and diallylic proton resonance (measured at TE=50 ms) areas correlated with the olefinic (R=0.993, SE 0.33) and diallylic (R=0.997, SE 0.19) proton contents calculated from the GC data. Information derived from long echo time spectra (TE=200) demonstrated good correlations to GC data and showed no change with increasing temperature (and T(2)). In (1)H NMR spectra (1.5T) of adipose tissue in five healthy subjects, the analytically important olefinic and diallylic resonances were clearly resolved with a coefficient of variation of 1.6% and 8.4%, respectively, for repeated measurements. The characteristic phase behavior of the omega-3 methyl outer triplet line at 1.08 ppm could also be detected at very long echo times (470 and 540 ms).
Fatty acid composition has an impact on the echo time behavior of triglyceride resonances. Long TE spectra can resolve omega-3 FA in adipose tissue in vivo. These findings will benefit long TE studies of tissue lipids.
本研究在临床环境中调查了脂肪酸（FA）组成对甘油三酯共振回波时间行为的影响。还评估了体内人体脂肪组织中利用氢核磁共振波谱法检测这些共振的可行性。
选择十种涵盖广泛FA组成的食用油作为模型材料。分别通过气相色谱法和高分辨率氢核磁共振波谱法（11.7T）对油的详细FA组成和固有质子光谱进行表征。随后在临床扫描仪（1.5T）中使用激励回波采集模式（PRESS）通过氢核磁共振波谱法测量油的详细回波时间行为。在五种油中研究了温度的影响。
烯烃（5.3 ppm）和二烯丙基（2.8 ppm）共振呈现出与油的FA组成无关的独特J调制模式。亚甲基共振（1.3 ppm）呈现指数衰减，表观横向弛豫时间（T(2)）与油的不饱和度呈弱正相关（R = 0.628，P = 0.052），这可能是粘度变化的结果。对于甲基共振（0.9 ppm），富含ω-3脂肪酸的油与非ω-3油相比呈现出明显不同的J调制模式。ω-3甲基基团的特征J调制可归因于ω-3甲基三重峰信号的相位行为（在135 ms的回波时间处所有三重峰线同相），这是ω-3甲基端形成一级自旋系统的结果。在回波时间为140 ms的谱图中，1.08 ppm处的ω-3甲基外部三重峰线被发现可用于确定油中的ω-3含量（R = 0.999，估计标准误差（SE）为0.80）。烯烃和二烯丙基质子共振（在回波时间为50 ms时测量）面积与根据气相色谱数据计算出的烯烃（R = 0.993，SE为0.33）和二烯丙基（R = 0.997，SE为0.19）质子含量相关。从长回波时间谱图（回波时间 = 200）获得的信息与气相色谱数据显示出良好的相关性，并且随着温度（和T(2)）升高没有变化。在五名健康受试者的脂肪组织的氢核磁共振波谱图（1.5T）中，分析上重要的烯烃和二烯丙基共振清晰可辨，重复测量的变异系数分别为1.6%和8.4%。在非常长的回波时间（470和540 ms）也能检测到1.08 ppm处ω-3甲基外部三重峰线的特征相位行为。
脂肪酸组成对甘油三酯共振的回波时间行为有影响。长回波时间谱图可在体内分辨脂肪组织中的ω-3脂肪酸。这些发现将有利于组织脂质的长回波时间研究。
