Amin Naima, Afzal Mohammad
Department of Physics, The Islamia University of Bahawalpur, Pakistan.
J Pak Med Assoc. 2009 Apr;59(4):231-5.
To evaluate the practical impact of alteration of key imaging parameters of Magnetic Resonance Imaging on image quality and effectiveness provided by widely available fast imaging pulse sequences.
A tissue equivalent material for Magnetic resonance Imaging (MRI) has been produced from a polysaccharide gel, agros, containing gadolinium chloride chelated to Ethylene Diamine Tetra- Acetic acid (EDTA) with a sort of T1 and T2 values. Experimental variations in key parameters included echo time (TE) and repetition time TR. Quantitative analysis consisted of image nonuniformity.
In T2 weighted images; any change in TE played a critical role in the signal homogeneity in all pulse sequences. The percentage of nonuniformity was incredibly high in T2 weighted image but the change of TR was insignificant in T2-weighted study. Involving T1 weighted images, percentage of nonuniformity was high in gradient recalled echo (GRE), also noticeable in fast fluid attenuated recovery (FLAIR) but quite acceptable in fast spin echo (FSE) and conventional spin echo (CSE).
Selection of parameters relatively simple in CSE both in T1, T2-weighted study that maintains image uniformity and quality as well. GRE is a very sensitive pulse sequence for any variation in parameters and loose signal uniformity rapidly.
评估磁共振成像关键成像参数的改变对广泛应用的快速成像脉冲序列所提供的图像质量和有效性的实际影响。
用一种含有与乙二胺四乙酸（EDTA）螯合的氯化钆且具有一定T1和T2值的多糖凝胶琼脂糖制备了一种用于磁共振成像（MRI）的组织等效材料。关键参数的实验变化包括回波时间（TE）和重复时间（TR）。定量分析包括图像不均匀性。
在T2加权图像中；TE的任何变化在所有脉冲序列的信号均匀性方面都起着关键作用。T2加权图像中的不均匀百分比极高，但在T2加权研究中TR的变化不显著。在T1加权图像中，梯度回波（GRE）中的不均匀百分比很高，快速液体衰减反转恢复（FLAIR）中也很明显，但在快速自旋回波（FSE）和传统自旋回波（CSE）中相当可接受。
在T1、T2加权研究中，CSE中参数的选择相对简单，既能保持图像的均匀性又能保持图像质量。GRE对参数的任何变化都是非常敏感的脉冲序列，会迅速失去信号均匀性。
