Visualization of pressure distribution within loaded joint cartilage by application of angle-sensitive NMR microscopy

High-resolution MRI measurements on knee joints show a multilaminar appeara nce of the cartilage. This intracartilaginar structure, visualized as hypoi ntense zones in T-2-weighted MR images is based on the dipolar interaction of water molecules within regions of anisotropic arrangement of collagen ne twork. Using the different angle dependence of the MR signal, tones of radi ally and tangentially oriented network structures can be distinguished. Inf ormation equivalent to that from polarization light microscopy can be deriv ed noninvasively, This is demonstrated by polarization light microscopic re ference investigations, It is shown that this multilaminar MRI appearance i s sensitively influenced by mechanical stress. A model explaining the contr ary behavior of loaded tangential and radial network structures is given. B ased on this pressure dependence, a noninvasive determination of mechanical properties is possible. Using the variation of size and intensity of the h ypointense zones under pressure, dynamic high resolution MRI yields noninva sive information about the intracartilaginar pressure distribution similar to photoelastic measurements. Magn Reson Med 43:884-891, 2000. (C) 2000 Wil ey-Liss, Inc.