Koutcher J A, Burt C T, Lauffer R B, Brady T J
J Nucl Med. 1984 Apr;25(4):506-13.
The demand for higher diagnostic specificity has led to the increased use of "foreign" agents to increase tissue contrast and/or spectroscopic sensitivity in NMR studies. The primary agents used to enhance tissue contrast in NMR imaging are paramagnetic. They cause a decrease in the proton T1 of H2O leading to enhanced signal intensity. This effect depends on the large gyromagnetic ratio of the electron, the number of unpaired electrons, the concentration of paramagnetic ions, the number of coordinated water molecules, and the rate of exchange of water. Spectroscopic enhancement has relied primarily on attempt at isotopic enrichment (usually C-13), which causes a direct increase in signal.
对更高诊断特异性的需求导致在核磁共振（NMR）研究中更多地使用“外来”试剂以提高组织对比度和/或光谱灵敏度。用于增强NMR成像中组织对比度的主要试剂是顺磁性的。它们会导致H2O的质子T1降低，从而增强信号强度。这种效应取决于电子的大旋磁比、未成对电子的数量、顺磁性离子的浓度、配位水分子的数量以及水的交换速率。光谱增强主要依赖于同位素富集（通常是C-13）的尝试，这会直接增加信号。
