Peto S, Gillis P
Groupe de résonance magnétique nucléaire, Faculté de médecine, Université de Mons-Hainaut, Belgium.
Magn Reson Imaging. 1990;8(6):705-12. doi: 10.1016/0730-725x(90)90005-m.
Longitudinal and transverse proton relaxation times were measured on pig tendon. For T1, dispersion curves and more accurate measurements at 20 MHz are presented. Values of T2 were obtained from CPMG pulse sequences, at 20 MHz. The dependence of relaxation times against the fiber-to-field angle was particularly investigated. Longitudinal relaxation rate was found to be almost orientation independent, and presented quadrupolar peaks between 1 and 4 MHz. On the contrary, transverse relaxation, that was well fitted by the sum of four exponentials, was highly orientation dependent. Deconvolution showed that the exponentials decaying most quickly are most orientation dependent. For those two fractions, a cross-relaxation model allowed explaining the fiber-to-field angle dependence, and the specially low rate corresponding to the magic angle of 55 degrees. Finally, each decaying mode was assigned to a fraction of protons localized in the macromolecular structure and characterized by particular dynamics.
在猪肌腱上测量了纵向和横向质子弛豫时间。对于T1，给出了色散曲线以及在20MHz下更精确的测量结果。T2值是通过CPMG脉冲序列在20MHz下获得的。特别研究了弛豫时间与纤维到场方向夹角的关系。发现纵向弛豫率几乎与方向无关，并且在1至4MHz之间出现四极峰。相反，横向弛豫由四个指数之和很好地拟合，高度依赖于方向。去卷积表明，衰减最快的指数对方向的依赖性最强。对于这两个部分，交叉弛豫模型可以解释纤维到场方向夹角的依赖性以及对应于55度魔角的特别低的速率。最后，每个衰减模式都被分配给大分子结构中特定质子部分，并由特定动力学特征表征。
