Chang Kevin J, Kamel Ihab R, Macura Katarzyna J, Bluemke David A
Department of Diagnostic Imaging, Rhode Island Hospital and The Miriam Hospital, Warren Alpert Medical School of Brown University, Providence, RI 02903, USA.
Radiographics. 2008 Nov-Dec;28(7):1983-98. doi: 10.1148/rg.287075154.
Three-tesla magnetic resonance (MR) imaging offers substantially higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) than 1.5-T MR imaging does, which can be used to improve image resolution and shorten imaging time. Because of these increases in SNR and CNR, as well as changes in T1 and T2 relaxation times, an increase in magnetic susceptibility, and an increase in chemical shift effect, many abdominal applications can benefit from 3.0-T imaging. Increased CNR obtained with a gadolinium-based contrast agent improves lesion conspicuity, requires less intravenous contrast material, and improves MR angiography by increasing spatial and temporal resolution. Increased SNR improves fluid conspicuity and resolution for applications such as MR cholangiopancreatography. Increased chemical shift effect also improves spectral resolution for MR spectroscopy. Several potential problems remain for abdominal imaging at 3.0 T. Limitations on energy deposition may require compromises in pulse sequence timing and flip angles. These compromises result in prolonged imaging time and altered image contrast. Magnetic susceptibility and chemical shift artifacts are worsened, but they may be counteracted by shortening echo time, performing parallel imaging, and increasing bandwidth. Radiofrequency field inhomogeneity is also a major concern in imaging larger fields of view and often leads to standing wave effects and large local variations in signal intensity. Many issues related to MR device compatibility and safety have yet to be addressed at 3.0 T. A 3.0-T MR imaging system has a higher initial cost and a higher cost of upkeep than a 1.5-T system does.
3特斯拉磁共振（MR）成像提供的信噪比（SNR）和对比噪声比（CNR）比1.5特斯拉MR成像显著更高，可用于提高图像分辨率并缩短成像时间。由于SNR和CNR的这些提高，以及T1和T2弛豫时间的变化、磁化率的增加和化学位移效应的增加，许多腹部应用可受益于3.0-T成像。使用钆基造影剂获得的CNR增加可提高病变的可见性，减少静脉内造影剂用量，并通过提高空间和时间分辨率改善磁共振血管造影。SNR的增加改善了诸如磁共振胰胆管造影等应用中液体的可见性和分辨率。化学位移效应的增加也提高了磁共振波谱的频谱分辨率。3.0 T腹部成像仍存在一些潜在问题。能量沉积的限制可能需要在脉冲序列定时和翻转角度上做出妥协。这些妥协导致成像时间延长和图像对比度改变。磁化率和化学位移伪影会恶化，但可通过缩短回波时间、进行并行成像和增加带宽来抵消。射频场不均匀性在大视野成像中也是一个主要问题，并且常常导致驻波效应和信号强度的大局部变化。在3.0 T时，许多与MR设备兼容性和安全性相关的问题尚未得到解决。3.0-T MR成像系统的初始成本和维护成本比1.5-T系统更高。
