Ferrucci J T
Department of Radiology, Boston University School of Medicine, Boston Medical Center, MA 02118, USA.
Radiographics. 1998 Nov-Dec;18(6):1569-86. doi: 10.1148/radiographics.18.6.9821200.
Major technical advances in MR imaging have led to its wider use in the evaluation of abdominal disease. The principle new pulse sequence is the RARE sequence for T2-weighted imaging. Multishot and breath-hold single-shot RARE techniques are now widely used, and both have performed as well as conventional spin-echo imaging with far shorter acquisition times. The most notable improvements have been in the detection and characterization of hepatic lesions. Two liver-specific contrast agents received FDA approval during 1997: SPIO particles or ferumoxide and mangafodipir trisodium, a hepatocyte-specific agent. Both of these agents provide considerable benefit in the detection and characterization of hepatic lesions. Manganese enhancement has also proved useful in MR imaging of the pancreas, although fat-suppressed T1-weighted imaging with dynamic gadolinium enhancement has also yielded results comparable with those of contrast-enhanced CT. MR hydrography, a generic term for static fluid imaging, is another derivative of RARE fast T2-weighted imaging. MRCP, the best known example of MR hydrography, has been rapidly and widely employed as a primary method for imaging the biliary and pancreatic ducts and has become competitive with ERCP. MR vascular imaging, especially portal venography, has been used for noninvasive imaging of portal venous disease in Budd Chiari disease, before placement of transjugular intrahepatic portosystemic shunts, and for pancreatic cancer staging. Finally, the development of conventional phased-array body coils and endorectal coils has enabled high-quality MR imaging of perirectal disease (including Crohn disease, fistula in ano, and postpartum sphincter dysfunction). Future abdominal applications of MR imaging will involve second-generation MR interventional techniques, including use of open systems, functional or diffusion-weighted imaging exploiting the molecular activity of tissues, and virtual MR endoscopy. Although CT continues to evolve as the premier technique for survey screening of the abdomen, the technical advances in MR imaging have enabled this modality to assume some special nitch roles (in which it adds unique value) in the evaluation of the abdomen. Radiologists can safely assume that there will undoubtedly be much more to come.
磁共振成像（MR）技术的重大进展使其在腹部疾病评估中的应用更为广泛。主要的新型脉冲序列是用于T2加权成像的快速采集弛豫增强（RARE）序列。多次激发和屏气单次激发RARE技术目前已被广泛应用，且二者在采集时间远短于传统自旋回波成像的情况下，成像效果与传统自旋回波成像相当。最显著的改进在于肝脏病变的检测和特征分析。1997年，两种肝脏特异性造影剂获得了美国食品药品监督管理局（FDA）的批准：超顺磁性氧化铁（SPIO）微粒或铁葡聚糖，以及一种肝细胞特异性造影剂——锰福地匹三钠。这两种造影剂在肝脏病变的检测和特征分析方面均提供了显著的帮助。锰增强在胰腺的MR成像中也已证明是有用的，尽管脂肪抑制T1加权成像结合动态钆增强也已产生了与对比增强CT相当的结果。MR水成像，即静态液体成像的通用术语，是RARE快速T2加权成像的另一个衍生技术。磁共振胰胆管造影（MRCP）是MR水成像最著名的例子，已迅速且广泛地被用作胆管和胰管成像的主要方法，并已与内镜逆行胰胆管造影（ERCP）形成竞争。MR血管成像，尤其是门静脉造影，已被用于布加综合征门静脉疾病的无创成像、经颈静脉肝内门体分流术（TIPS）放置前的评估以及胰腺癌分期。最后，传统相控阵体线圈和直肠内线圈的发展使得对直肠周围疾病（包括克罗恩病、肛瘘和产后括约肌功能障碍）进行高质量的MR成像成为可能。MR成像未来在腹部的应用将涉及第二代MR介入技术，包括开放系统的使用、利用组织分子活性的功能或扩散加权成像以及虚拟MR内镜检查。尽管CT作为腹部普查筛查的首要技术仍在不断发展，但MR成像的技术进步已使该检查手段在腹部评估中承担了一些特殊的细分角色（在这些角色中它能提供独特的价值）。放射科医生可以放心地认为，毫无疑问，未来还会有更多的进展。
