Petrou Myria, Sundgren Pia C, Pang Yuxi, Rohrer Suzan, Foerster Bradley, Chenevert Thomas L
Department of Radiology, University of Michigan Health System, 1500 E. Medical Center Drive, Ann Arbor, MIMI 48109-0030, USA.
Acad Radiol. 2007 Mar;14(3):340-3. doi: 10.1016/j.acra.2006.12.011.
Metabolite peak boundary definition is an important postprocessing step in proton magnetic resonance spectroscopy (1H-MRS). We compare metabolite ratios calculated using three different postprocessing strategies: software-rendered default peak boundaries, manually adjusted peak boundaries and a curve-fitting program. The first two of these methods are commercially available.
A total of 42 spectra acquired on a 1.5-T MR unit using two-dimensional chemical shift proton MR spectroscopy (TR/TE = 1500/144 ms) were analyzed. Choline (Cho), creatine (Cr), and N-acetylaspartate (NAA) relative concentrations were derived and the following metabolite ratios were calculated: Cho/Cr, Cho/NAA, and NAA/Cr. Metabolite concentrations/ratios were calculated using (a) default peak boundaries rendered by commercially available, postprocessing software (Functool 2000, version 2.6.0); (b) manually adjusted peak boundaries by an experienced spectroscopist, using an option offered by the same commercially available software; and (c) an offline in-house curve-fitting program. Measurements obtained with method (c) were considered as the "gold standard." Paired t-tests comparing default and adjusted metabolite ratios, as well as default and adjusted ratios with their respective curve-fit values were used for statistical analysis.
Significant differences between default and manually adjusted values were found for Cho/Cr ratios <1.5 and for all Cho/NAA ratios. For Cho/Cr ratios <1.5, significant differences between default and curve-fit values were present; this was not the case when comparing manually adjusted and curve-fit values. Default and manually adjusted Cho/NAA ratios were significantly higher than corresponding curve-fit ratios. Manually adjusted values were, however, closer to the curve-fit values. No significant differences were noted between default and adjusted NAA/Cr values; default and manually adjusted ratios were significantly lower than curve-fit ratios.
There can be significant differences in metabolite ratios calculated using default and manually adjusted peak limits in proton MR spectroscopy. Furthermore, Cho/Cr and NAA/Cho adjusted metabolite ratios are closer to curve-fit values, which are considered the most accurate of the three.
代谢物峰边界定义是质子磁共振波谱（1H-MRS）中一个重要的后处理步骤。我们比较了使用三种不同后处理策略计算的代谢物比率：软件渲染的默认峰边界、手动调整的峰边界和曲线拟合程序。前两种方法可通过商业途径获得。
使用二维化学位移质子磁共振波谱（TR/TE = 1500/144 ms）在1.5-T MR设备上采集了42个光谱并进行分析。得出胆碱（Cho）、肌酸（Cr）和N-乙酰天门冬氨酸（NAA）的相对浓度，并计算以下代谢物比率：Cho/Cr、Cho/NAA和NAA/Cr。代谢物浓度/比率使用以下方法计算：（a）由商用后处理软件（Functool 2000，版本2.6.0）渲染的默认峰边界；（b）由经验丰富的波谱学家使用同一商用软件提供的选项手动调整峰边界；（c）一个离线的内部曲线拟合程序。用方法（c）获得的测量值被视为“金标准”。使用配对t检验比较默认和调整后的代谢物比率，以及默认和调整后的比率与其各自的曲线拟合值，进行统计分析。
发现Cho/Cr比率<1.5以及所有Cho/NAA比率时，默认值和手动调整值之间存在显著差异。对于Cho/Cr比率<1.5，默认值和曲线拟合值之间存在显著差异；而比较手动调整值和曲线拟合值时则不存在这种情况。默认和手动调整的Cho/NAA比率显著高于相应的曲线拟合比率。然而，手动调整值更接近曲线拟合值。默认和调整后的NAA/Cr值之间未发现显著差异；默认和手动调整的比率显著低于曲线拟合比率。
在质子磁共振波谱中，使用默认和手动调整的峰限值计算的代谢物比率可能存在显著差异。此外，调整后的Cho/Cr和NAA/Cho代谢物比率更接近曲线拟合值，在这三种方法中曲线拟合值被认为是最准确的。
