Wang Jinghua, Qiu Maolin, Constable R Todd
Department of Diagnostic Radiology, Yale University School Medical Center, The Anlyan Center, 300 Cedar Street, New Haven, CT 06510, USA.
Magn Reson Med. 2005 Mar;53(3):666-74. doi: 10.1002/mrm.20377.
Phased array coils are finding widespread applications in both the research and the clinical setting. However, intensity nonuniformities with such coils can reduce the potential benefits of these coils, particularly for applications such as tissue segmentation. In this work, a method is described for correcting the nonuniform signal response based on in vivo measures of both the transmission field of body coil and the reception sensitivity of phased array coils, separately. For a uniform phantom, the reception sensitivity can be calculated using both Bloch equations and transmission field maps. For a heterogeneous object such as a brain, a minimal contrast acquisition must be obtained to map the receiver nonuniformities. This transmit field/receiver sensitivity (TFRS) approach is compared with the standard methods of using the body coil to obtain a reference scan and low-pass filtering. The quantitative comparison results shows that the TFRS approach provides superior results in correcting intensity nonuniformities for a uniform phantom. This approach reduces the ratio between signal intensity SD of an image and its mean intensity from approximately 21% before correction to 13% after correction. Results are also shown demonstrating the utility of this approach in vivo with human brain images. The method is general and can be applied with most pulse sequences, any coil combination for transmission and reception, and in any anatomic region.
相控阵线圈在研究和临床环境中都有广泛的应用。然而，此类线圈产生的强度不均匀性会降低这些线圈的潜在优势，尤其是在组织分割等应用中。在这项工作中，描述了一种基于分别对体线圈的发射场和相控阵线圈的接收灵敏度进行活体测量来校正非均匀信号响应的方法。对于均匀体模，可以使用布洛赫方程和发射场图来计算接收灵敏度。对于像大脑这样的异质物体，必须获取最小对比度采集来绘制接收器的不均匀性。将这种发射场/接收器灵敏度（TFRS）方法与使用体线圈获得参考扫描和低通滤波的标准方法进行了比较。定量比较结果表明，TFRS方法在校正均匀体模的强度不均匀性方面提供了更好的结果。这种方法将图像的信号强度标准差与其平均强度之比从校正前的约21%降低到校正后的13%。结果还表明了该方法在人脑图像活体应用中的实用性。该方法具有通用性，可应用于大多数脉冲序列、任何发射和接收的线圈组合以及任何解剖区域。
