| 摘要 |
The subject matter of the invention concerns the anisotropic diffusion phantom for the calibration of any diffusion MR-DTI imaging sequence and a method for the calibration of all the MRI scanners by using anisotropic diffusion models based on the “b” matrix, which is a quantity specific for every magnetic resonance (MR) imaging sequence and the MRI scanner used. It has application in the study of solids, amorphous materials, liquids and biological tissues. The anisotropic diffusion phantom for the calibration of any MR imaging sequence is any anisotropic diffusion model of any shape for the hydrogen H2 contained in H2O or LC, for example. The diffusion standard according to the invention is preferably a pipe with a bundle of capillaries filled with H2O, hydrogel or any other substance that contains hydrogen nuclei or any volume, preferably cylindrical, filled with H2O, hydrogel or any other substance that contains hydrogen nuclei or densely filled with non-magnetic cylindrical rods free of hydrogen nuclei. In another embodiment, the diffusion model is an array of thin glass plates (1) separated with layers of H2O, hydrogel or any other substance that contains hydrogen nuclei (2). The model, being a pipe with a bundle of capillaries, has the capillaries selected so that the restriction of diffusion at a temperature in the direction perpendicular to the capillary axis is significant with respect to the range of diffusion times &Dgr; in the diffusion MR imaging sequence. For the calibration of any MR imaging sequence using the anisotropic diffusion phantom of the invention, the anisotropic diffusion phantom is placed in the volume of the MRI scanner tested. Subsequently, the number of “b” matrices needed for the calculation of the diffusion tensor is determined based on the anisotropic diffusion model. This constitutes no less than six “b” matrices as defined spatially for each voxel and for the specific directions of the diffusion gradient vector. Therefore, in the simplest case, 36 “b” matrices and one “bo” matrix without diffusion gradients are determined. The anisotropic diffusion phantom is a diffusion model for which the diffusion tensor in the system of principal axes assumes known values. The diffusion model is rotated by various Euler angles, so that the determinant DM of the matrix whose columns correspond to the components of the diffusion tensor D is different from zero after each rotation. |
