Inglese M, Spindler M, Babb J S, Sunenshine P, Law M, Gonen O
Department of Radiology, New York University School of Medicine, New York, NY 10016, USA.
AJNR Am J Neuroradiol. 2006 Mar;27(3):684-8.
Clinical MR imaging scanners now offer many choices of hardware configurations that were not available in the first 25 years of their existence. Our goal was to assess the influence of coil technology, magnetic field strength, and echo time (TE) on the sensitivity, reflected by the signal intensity-to-noise-ratio (SNR) and reproducibility of proton MR spectroscopy (1H-MR spectroscopy).
The SNR, the intersubject reproducibility, and the intrasubject reproducibility of N-acetylaspartate (NAA), creatine (Cr), and choline (Cho) levels were compared at the common TEs of 30, 144, and 288 ms, by using 1H-MR spectroscopy in 6 volunteers at (1) 3T with a single-element quadrature (SEQ); (2) 1.5T with SEQ; and (3) 1.5T with a 12-channel phased-array (PA) head coil.
In terms of sensitivity, the best SNR for all metabolites was obtained at the shortest TE (30 ms). It was comparable between the 3 and 1.5T with the PA, but approximately 35% better than the 1.5T with SEQ. This SNR difference declined <25% at TE of 144 ms and to equity among all imagers at TE of 288 ms. Reproducibility, reflected in the coefficient of variation (CV), was best for NAA at TE of 288 ms, 15%-50% better than at TE of 30 ms in either gray (GM) or white matter (WM). The CV for Cr was best, at TE of 288 ms for GM, but its WM results were independent of TE. Metabolite level reproducibility did not depend on coil technology or magnetic field strength.
For the same coil type, the SNR of all major metabolites was approximately 35% better at 3T than at 1.5T. This advantage, however, was offset at 1.5T with a PA coil, making it a cost-effective upgrade for existing scanners. Surprisingly and counterintuitively, despite the lowest SNR, the best reproducibility was obtained at the longest TE (288 ms), regardless of field or coil.
临床磁共振成像扫描仪如今提供了许多在其发展的最初25年中所没有的硬件配置选择。我们的目标是评估线圈技术、磁场强度和回波时间（TE）对质子磁共振波谱（1H-MR波谱）的灵敏度（由信号强度与噪声比（SNR）反映）和可重复性的影响。
通过在6名志愿者中使用1H-MR波谱，在30、144和288 ms的常见TE下，比较了N-乙酰天门冬氨酸（NAA）、肌酸（Cr）和胆碱（Cho）水平的SNR、受试者间可重复性和受试者内可重复性，分别为：（1）3T单元素正交线圈（SEQ）；（2）1.5T SEQ；（3）1.5T 12通道相控阵（PA）头部线圈。
就灵敏度而言，所有代谢物在最短TE（30 ms）时获得最佳SNR。3T和带PA的1.5T之间相当，但比带SEQ的1.5T约好35%。在144 ms的TE时，这种SNR差异下降<25%，在288 ms的TE时所有成像仪之间相当。以变异系数（CV）反映的可重复性，对于NAA在288 ms的TE时最佳，在灰质（GM）或白质（WM）中比在30 ms的TE时好15%-50%。Cr的CV最佳，在GM中为288 ms的TE时，但在WM中的结果与TE无关。代谢物水平可重复性不依赖于线圈技术或磁场强度。
对于相同的线圈类型，所有主要代谢物在3T时的SNR比在1.5T时约好35%。然而，这种优势在带PA线圈的1.5T时被抵消，使其成为现有扫描仪的一种经济有效的升级选择。令人惊讶且与直觉相反的是，尽管SNR最低，但在最长TE（288 ms）时获得了最佳可重复性，与场强或线圈无关。
