Ruel Lucile, Brugières Pierre, Luciani Alain, Breil Stéphane, Mathieu Didier, Rahmouni Alain
Départment Imagerie Médicale, Centre Hospitalo-Universitaire Henri Mondor, Université de Créteil, Paris XII, 51 Ave. du Marechal de Lattre de Tassigny, Créteil 94010 Cedex, France.
AJR Am J Roentgenol. 2004 Mar;182(3):749-55. doi: 10.2214/ajr.182.3.1820749.
The purpose of this study was to compare the image quality of two parallel-imaging methods applied to standard turbo spin-echo T2-weighted imaging of the lumbar spine.
Phantom imaging and lumbar spine studies of 15 healthy subjects were performed using T2-weighted turbo spin-echo sequences obtained with and without parallel imaging (generalized autocalibrating partially parallel acquisition [GRAPPA] and modified sensitive encoding [mSENSE]) on a 1.5-T magnet. The signal-to-noise ratio (SNR) and uniformity were measured in the phantom, and SNR and signal difference-noise ratio were evaluated in cerebrospinal fluid, vertebral bodies, and subcutaneous fat of the volunteers, using both techniques sequentially. Aliasing artifacts on GRAPPA and mSENSE images were visually evaluated. SNRs were compared using the Student's paired t test, with p values less than 0.05 considered significant.
In the phantom study, when the same number of coil elements were used (n = 3), SNR and uniformity values obtained with standard T2-weighted turbo spin-echo sequences were higher than those obtained with parallel sequences. The GRAPPA SNR obtained with three coil elements was higher than the standard T2-weighted SNR obtained with one coil element. Similar findings were noted regarding uniformity. In the lumbar spine, GRAPPA SNR values for fat, cerebrospinal fluid, and vertebral bodies were significantly higher than mSENSE SNR values, with a p value less than 0.01, but were not significantly different from T2-weighted turbo spin-echo SNR values. GRAPPA signal difference-noise ratio values were significantly higher than mSENSE signal difference-noise ratio values, with a p value less than 0.01, but were not significantly different from T2-weighted turbo spin-echo signal difference-noise ratio values. GRAPPA produced fewer aliasing artifacts than mSENSE.
In spine MRI, GRAPPA may be used to reduce scanning time and yields a higher SNR than mSENSE without any increase in aliasing artifacts and with an SNR similar to that obtained with standard T2-weighted turbo spin-echo.
本研究旨在比较两种并行成像方法应用于腰椎标准快速自旋回波T2加权成像时的图像质量。
对15名健康受试者进行体模成像和腰椎研究，使用1.5-T磁共振仪上在有和没有并行成像（广义自校准部分并行采集[GRAPPA]和改良灵敏度编码[mSENSE]）的情况下获得的T2加权快速自旋回波序列。在体模中测量信噪比（SNR）和均匀性，并在志愿者的脑脊液、椎体和皮下脂肪中依次使用两种技术评估SNR和信号差异噪声比。对GRAPPA和mSENSE图像上的混叠伪影进行视觉评估。使用配对t检验比较SNR，p值小于0.05认为具有统计学意义。
在体模研究中，当使用相同数量的线圈单元（n = 3）时，标准T2加权快速自旋回波序列获得的SNR和均匀性值高于并行序列获得的值。三个线圈单元获得的GRAPPA SNR高于一个线圈单元获得的标准T2加权SNR。在均匀性方面也有类似发现。在腰椎中，脂肪、脑脊液和椎体的GRAPPA SNR值显著高于mSENSE SNR值，p值小于0.01，但与T2加权快速自旋回波SNR值无显著差异。GRAPPA信号差异噪声比值显著高于mSENSE信号差异噪声比值，p值小于0.01，但与T2加权快速自旋回波信号差异噪声比值无显著差异。GRAPPA产生的混叠伪影比mSENSE少。
在脊柱MRI中，GRAPPA可用于减少扫描时间，并且在不增加混叠伪影的情况下产生比mSENSE更高的SNR，且其SNR与标准T2加权快速自旋回波获得的SNR相似。
