Department of Radiology, Thomas Jefferson University, 132 S. 10th Street, Philadelphia, PA 19107, USA.
Radiographics. 2010 Jan;30(1):185-99. doi: 10.1148/rg.301095076.
Abdominal magnetic resonance (MR) imaging involves many challenges and is complicated by physiologic motion not encountered to the same degree in other regions of the body. Problems that uniquely affect abdominal MR imaging include motion artifact (from respiratory, cardiac, gastrointestinal, and voluntary movement), susceptibility artifact, conductive and dielectric effects, and wraparound artifact. Techniques to minimize these artifacts often need to be addressed within the time constraints of a single breath hold. Patient motion during image acquisition is minimized by using physical restraint, respiratory gating, and reduction of acquisition time. Correction of motion-induced dephasing (through gradient moment nulling), signal averaging, and suppression of signal in moving structures all address unavoidable motion (eg, cardiac pulsation). Acquisition time is minimized by obtaining fewer phase-encoding steps, decreasing repetition time, and increasing efficiency with use of parallel imaging and multiecho acquisitions. Adjusting the echo time does not directly affect scanning time, but it does allow more time for section sampling per repetition time interval in multisection acquisitions by means of closer echo spacing and it plays a pivotal role in optimizing image quality. Familiarity with basic MR imaging principles and the ability to minimize the effects of motion and other artifacts are essential to optimizing abdominal MR imaging protocols and improving efficiency.
腹部磁共振（MR）成像是一个充满挑战的过程，由于人体腹部器官的生理运动与其他部位不同，因此腹部 MR 成像更为复杂。独特影响腹部 MR 成像的问题包括运动伪影（来自呼吸、心脏、胃肠道和自主运动）、磁化率伪影、传导和介电效应以及绕射伪影。为了尽量减少这些伪影，通常需要在单次屏气的时间限制内解决技术问题。通过使用物理约束、呼吸门控和减少采集时间来最小化图像采集期间的患者运动。通过梯度矩置零、信号平均和移动结构信号抑制来校正运动引起的去相位（通过梯度矩置零），所有这些都可以解决不可避免的运动（例如心脏搏动）。通过减少相位编码步骤、缩短重复时间和使用并行成像和多回波采集提高效率，来最小化采集时间。调整回波时间不会直接影响扫描时间，但通过更紧密的回波间隔，可以在多段采集的每个重复时间间隔内为部分采样提供更多时间，并且在优化图像质量方面发挥着关键作用。熟悉基本的磁共振成像原理并能够最大限度地减少运动和其他伪影的影响，对于优化腹部磁共振成像方案和提高效率至关重要。
