Lin Yi-Ru, Chiu Jian-Jia, Tsai Shang-Yueh
Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan.
Graduate Institute of Applied Physics, National Chengchi University, Taipei, Taiwan.
PLoS One. 2014 Dec 16;9(12):e114436. doi: 10.1371/journal.pone.0114436. eCollection 2014.
1H-MRS is widely regarded as the most accurate noninvasive method to quantify hepatic fat content (HFC). When practical period of breath holding, and acquisition of HFC over multiple liver areas is considered, a fast MR spectroscopic imaging technique is desired. The aim of this study is to examine the feasibility and reproducibility of echo planar spectroscopic imaging (EPSI) on the quantification of HFC in subject with various HFCs.
Twenty two volunteers were examined in a 3T MR system. The acquisition time of proposed EPSI protocol was 18 seconds. The EPSI scans were repeated 8 times for each subject to test reproducibility. The peak of water and individual peaks of fat including methyl, methylene, and allylic peaks at 0.9, 1.3, and 2.0 ppm were fitted. Calculated amount of water and fat content were corrected for T2 relaxation. The total HFC was defined as the combination of individual peaks. Standard deviation (SD), coefficient of variance (COV) and fitting reliability of HFC quantified by LCModel were calculated.
Our results show that the SDs of total HFC for all subjects are less than 2.5%. Fitting reliability is mostly under 10% and positively correlates with COV. Subjects separated into three subgroups according to quantified total HFC show that improved fitting reliability and reproducibility can be achieved on subjects with higher total HFC.
We have demonstrated feasibility of the proposed EPSI protocols on the quantification of HFC over a whole slice of liver with scan time in a single breath hold.
1H-磁共振波谱（1H-MRS）被广泛认为是定量肝脏脂肪含量（HFC）最准确的非侵入性方法。考虑到实际屏气时间以及在多个肝脏区域获取HFC时，需要一种快速磁共振波谱成像技术。本研究的目的是检验回波平面波谱成像（EPSI）在定量不同HFC水平受试者肝脏脂肪含量方面的可行性和可重复性。
22名志愿者在3T磁共振系统中接受检查。所提出的EPSI方案采集时间为18秒。对每位受试者的EPSI扫描重复8次以测试可重复性。对水峰以及脂肪的各个峰，包括0.9、1.3和2.0 ppm处的甲基、亚甲基和烯丙基峰进行拟合。计算得到的水和脂肪含量针对T2弛豫进行校正。总HFC定义为各个峰的总和。计算由LCModel定量的HFC的标准差（SD）、变异系数（COV）以及拟合可靠性。
我们的结果表明，所有受试者总HFC的SD均小于2.5%。拟合可靠性大多低于10%，且与COV呈正相关。根据定量的总HFC将受试者分为三个亚组，结果显示，对于总HFC较高的受试者，拟合可靠性和可重复性有所提高。
我们已经证明了所提出的EPSI方案在单次屏气扫描时间内对整个肝脏切片的HFC进行定量的可行性。
