Yu B C, Jara H, Vanhoenacker P K, Yucel E K
Department of Radiology, Boston University Medical Center, MA 02118, USA.
Magn Reson Imaging. 1997;15(3):267-73. doi: 10.1016/s0730-725x(96)00394-3.
The objectives of this study were to optimize T2-weighted hybrid-RARE pulse sequences for clinical MR imaging of the liver, and to compare them to the conventional spin-echo (CSE) sequence. Specifically, the ranges of the echo train length (ETL) and the effective echo time (TEeff) were investigated to optimize image quality and liver-spleen contrast, in healthy volunteers. A total of thirteen volunteers were scanned at 1.5 Tesla with an extensive array of hybrid-RARE scans. The images were analyzed quantitatively with respect to CNR (contrast-to-noise ratio of spleen vs. liver), SNR (signal to noise ratio of the spleen), SIR (signal intensity ratio of liver and spleen) and CDR (contrast difference ratio between the spleen and liver). The images were also analyzed qualitatively with respect to image sharpness, vascular artifacts, ghosting, chemical shift, and truncations. Results of quantitative analysis indicated that CDR and SIR of hybrid-RARE at higher ETL (> 13) were consistently better than both the reference CSE and the lower ETL sequences (p < 0.05) at all TEeff. SNR was slightly inferior for all hybrid-RARE sequences than for the CSE sequence. Image quality for hybrid-RARE sequences with ETL > 13 proved to be consistently better than that for the CSE (TE = 90 ms) with respect to imaging sharpness, vascular artifacts and ghosting artifacts (p < 0.05). In conclusion, the optimized hybrid-RARE sequences with ETL greater than or equal to 13 are capable of producing sharp and relatively artifact free images with the advantage of a much greater acquisition time efficiency.
本研究的目的是优化用于肝脏临床磁共振成像的T2加权混合快速自旋回波（hybrid-RARE）脉冲序列，并将其与传统自旋回波（CSE）序列进行比较。具体而言，在健康志愿者中研究回波链长度（ETL）和有效回波时间（TEeff）的范围，以优化图像质量和肝脾对比度。共有13名志愿者在1.5特斯拉磁场下进行了一系列广泛的混合RARE扫描。对图像进行了定量分析，涉及对比噪声比（CNR，脾脏与肝脏的对比噪声比）、信噪比（SNR，脾脏的信噪比）、信号强度比（SIR，肝脏与脾脏的信号强度比）和对比差异比（CDR，脾脏与肝脏之间的对比差异比）。还对图像进行了定性分析，涉及图像清晰度、血管伪影、重影、化学位移和截断。定量分析结果表明，在所有TEeff下，较高ETL（>13）的混合RARE的CDR和SIR始终优于参考CSE和较低ETL序列（p<0.05）。所有混合RARE序列的SNR略低于CSE序列。在成像清晰度、血管伪影和重影伪影方面，ETL>13的混合RARE序列的图像质量始终优于CSE（TE = 90 ms）（p<0.05）。总之，优化后的ETL大于或等于13的混合RARE序列能够产生清晰且相对无伪影的图像，并且具有更高的采集时间效率优势。
