关节软骨中的横向弛豫机制。

Transverse relaxation mechanisms in articular cartilage.

作者信息

Mlynárik V, Szomolányi P, Toffanin R, Vittur F, Trattnig S

机构信息

MR Center of Excellence, Department of Radiology, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria.

出版信息

J Magn Reson. 2004 Aug;169(2):300-7. doi: 10.1016/j.jmr.2004.05.003.

DOI:10.1016/j.jmr.2004.05.003

PMID:15261626

Abstract

Relaxation rates in the rotating frame (R1rho) and spin-spin relaxation rates (R2) were measured in articular cartilage at various orientations of cartilage layer to the static magnetic field (B0), at various spin locking field strengths and at two different static magnetic field strengths. It was found that R1rho in the deep radial zone depended on the orientation of specimens in the magnet and decreased with increasing the spin locking field strength. In contrast, R1rho values in the transitional zone were nearly independent of the specimen orientation and the spin locking field strength. Measurements of the same specimens at 2.95 and 7.05 T showed an increase of R1rho and most R2 values with increasing B0. The inverse B0 dependence of some R2 values was probably due to a multicomponent character of the transverse magnetization decay. The experiments revealed that the dominant T1rho and T2 relaxation mechanism at B0 < or = 3 T is a dipolar interaction due to slow anisotropic motion of water molecules in the collagen matrix. On average, the contribution of scalar relaxation due to rapid proton exchange in femoral head cartilage at 2.95 T is about 6% or less of the total R1rho at the spin locking field of 1000 Hz.

摘要

在软骨层相对于静磁场（B0）的不同取向、不同自旋锁定场强以及两种不同静磁场强度条件下，测量了关节软骨在旋转坐标系中的弛豫率（R1rho）和自旋 - 自旋弛豫率（R2）。研究发现，深层放射状区域的R1rho取决于样品在磁体中的取向，并随自旋锁定场强的增加而降低。相比之下，过渡区域的R1rho值几乎与样品取向和自旋锁定场强无关。在2.95 T和7.05 T对相同样品进行测量，结果显示随着B0增加，R1rho和大多数R2值升高。一些R2值对B0的反比关系可能归因于横向磁化衰减的多组分特性。实验表明，在B0≤3 T时，占主导地位的T1rho和T2弛豫机制是由于胶原基质中水分子缓慢各向异性运动引起的偶极相互作用。平均而言，在2.95 T时，股骨头软骨中由于快速质子交换导致的标量弛豫对1000 Hz自旋锁定场下总R1rho的贡献约为6%或更低。