Breitkreutz Dylan Y, Fallone B Gino, Yahya Atiyah
Department of Oncology, University of Alberta, Edmonton, AB, Canada.
Department of Medical Physics, Cross Cancer Institute, Edmonton, AB, Canada.
NMR Biomed. 2015 Oct;28(10):1324-31. doi: 10.1002/nbm.3387. Epub 2015 Aug 28.
The purpose of this work was to investigate the effect of J-coupling interactions on the quantification and T2 determination of 1.3-ppm lipid methylene protons at 3 T. The response of the 1.3-ppm protons of hexanoic, heptanoic, octanoic, linoleic and oleic acid was measured as a function of point-resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM) TE. In addition, a narrow-bandwidth refocusing PRESS sequence designed to rewind J-coupling evolution of the 1.3-ppm protons was applied to the five fatty acids, to corn oil and to tibial bone marrow of six healthy volunteers. Peak areas were plotted as a function of TE, and data were fitted to monoexponentially decaying functions to determine Mo (the extrapolated area for TE = 0 ms) and T2 values. In phantoms, rewinding J-coupling evolution resulted in 198%, 64%, 44%, 20% and 15% higher T2 values for heptanoic, octanoic, linoleic and oleic acid, and corn oil, respectively, compared with those obtained with standard PRESS. The narrow-bandwidth PRESS sequence also resulted in significant changes in Mo , namely -77%, -22%, 28%, 23% and 28% for heptanoic, octanoic, linoleic and oleic acid, and corn oil, respectively. T2 values obtained with STEAM were closer to the values measured with narrow-bandwidth PRESS. On average, in tibial bone marrow (six volunteers) rewinding J-coupling evolution resulted in 21% ± 3% and 9 % ± 1% higher Mo and T2 values, respectively. This work demonstrates that the consequence of neglecting to consider scalar coupling effects on the quantification of 1.3-ppm lipid methylene protons and their T2 values is not negligible. The linoleic and oleic acid T2 results indicate that T2 measures of lipids with standard MRS techniques are dependent on lipid composition.
本研究的目的是探究J耦合相互作用对3 T磁场下1.3 ppm脂质亚甲基质子定量及T2测定的影响。测量了己酸、庚酸、辛酸、亚油酸和油酸的1.3 ppm质子响应随点分辨光谱法（PRESS）和激励回波采集模式（STEAM）回波时间（TE）的变化。此外，将一种旨在消除1.3 ppm质子J耦合演化的窄带宽重聚焦PRESS序列应用于这五种脂肪酸、玉米油以及六名健康志愿者的胫骨骨髓。将峰面积绘制为TE的函数，并将数据拟合为单指数衰减函数以确定Mo（TE = 0 ms时的外推面积）和T2值。在模型中，与标准PRESS相比，消除J耦合演化使庚酸、辛酸、亚油酸、油酸和玉米油的T2值分别提高了198%、64%、44%、20%和15%。窄带宽PRESS序列还使Mo发生了显著变化，庚酸、辛酸、亚油酸、油酸和玉米油的Mo变化分别为-77%、-22%、28%、23%和28%。STEAM获得的T2值更接近窄带宽PRESS测量的值。平均而言，在胫骨骨髓（六名志愿者）中，消除J耦合演化使Mo和T2值分别提高了21%±3%和9%±1%。这项工作表明，在1.3 ppm脂质亚甲基质子定量及其T2值测定中忽略标量耦合效应的影响不可忽略。亚油酸和油酸的T2结果表明，标准磁共振波谱技术对脂质的T2测量取决于脂质组成。
