Smith F W
J Perinat Med. 1985;13(6):265-76. doi: 10.1515/jpme.1985.13.6.265.
Nuclear magnetic resonance (NMR) imaging is a new technique for in-vivo human imaging. The technique does not use ionizing radiation but employs a radiofrequency pulse and a strong magnetic field to map the hydrogen proton distribution in the body. Since most of the hydrogen in the body is present in either water or fat it is the best imaging method yet devised for displaying the soft tissues of the body. The principles of NMR imaging are briefly described in simple terms for the benefit of the reader not yet familiar with the technique before discussing its potential use in the study of the developing fetus. The absence of ionizing radiation together with the good resolution soft tissue images allow for accurate demonstration of the uterus, placenta and fetus in the pregnant patient. Prior to 22 weeks gestation the fetus may be difficult to image due to its movement during imaging. After 26 weeks the fetus is generally well demonstrated and measurements of fetal size easily made. Observations of the fetal brain, lungs, heart, liver and genito-urinary tract are possible and by measuring the strength of the NMR signal the development of these fetal organs may be made. In the fetus of the diabetic mother measurement of the fetal subcutaneous fat is possible and may be of use in assessing gestational age. The placenta is easily localized even when situated posteriorly. Observations of maternal organs are also possible, especially the kidneys and spine.
核磁共振（NMR）成像是一种用于人体活体成像的新技术。该技术不使用电离辐射，而是利用射频脉冲和强磁场来绘制体内氢质子的分布。由于体内大部分氢存在于水或脂肪中，所以它是目前设计出的用于显示人体软组织的最佳成像方法。在讨论其在发育中胎儿研究中的潜在用途之前，为了让尚未熟悉该技术的读者受益，将以简单的术语简要描述核磁共振成像的原理。电离辐射的缺失以及软组织图像的高分辨率，使得能够准确显示孕妇的子宫、胎盘和胎儿。在妊娠22周之前，由于胎儿在成像过程中的移动，可能难以成像。26周之后，胎儿通常能得到很好的显示，并且很容易测量胎儿大小。可以观察胎儿的脑、肺、心脏、肝脏和泌尿生殖道，通过测量核磁共振信号的强度，可以了解这些胎儿器官的发育情况。对于患有糖尿病母亲的胎儿，可以测量胎儿皮下脂肪，这可能有助于评估孕周。即使胎盘位于后方，也很容易定位。也可以观察母体器官，尤其是肾脏和脊柱。
