Anisotropic Diffusion Phantom For Calibration Of Diffusion Tensor Imaging Pulse Sequences Used In MRI

Abstract

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 H 2 contained in H 2 O or LC, for example. The diffusion standard according to the invention is preferably a pipe with a bundle of capillaries filled with H 2 O, hydrogel or any other substance that contains hydrogen nuclei or any volume, preferably cylindrical, filled with H 2 O, 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 H 2 O, 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 Δ 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 “b o ” 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 D M of the matrix whose columns correspond to the components of the diffusion tensor D is different from zero after each rotation.

1 . An anisotropic diffusion phantom forming a model for the calibration of an MR-DTI imaging sequence for an MR scanner at a specified temperature for a specified range of diffusion times, characterised in that it is formed by a volume densely filled with non-magnetic elements ( 1 ) aligned in parallel to at least one common parallel alignment axis and a substance ( 2 ) that contains hydrogen nuclei, the non-magnetic elements ( 1 ) and the substance ( 2 ) arranged such that diffusion of the substance ( 2 ) that contains hydrogen nuclei is significantly restricted in the direction perpendicular to the parallel alignment axis for the specified temperature with respect to the specified range of diffusion times. 
     
     
         2 . The anisotropic diffusion phantom according to  claim 2 , wherein the non-magnetic elements form a bundle of capillaries filled with the substance ( 2 ) that contains hydrogen nuclei. 
     
     
         3 . The anisotropic diffusion phantom according to  claim 2 , wherein the non-magnetic elements form a bundle of rods surrounded by the substance ( 2 ) that contains hydrogen nuclei. 
     
     
         4 . The anisotropic diffusion phantom according to  claim 2 , wherein the non-magnetic elements form an array of thin plates ( 1 ) between which the substance ( 2 ) that contains hydrogen nuclei is located. 
     
     
         5 . The anisotropic diffusion phantom according to  claim 2 , wherein the substance ( 2 ) that contains hydrogen nuclei is H 2 O or hydrogel. 
     
     
         6 . The anisotropic diffusion phantom according to  claim 2 , wherein the substance ( 2 ) that contains hydrogen nuclei comprises liquid crystals (LC). 
     
     
         7 . The anisotropic diffusion phantom according to  claim 2 , wherein the substance ( 2 ) that contains hydrogen nuclei comprises a substance containing  2 H,  3 He,  13 C,  14 N,  17 O,  19 F,  29 Si,  31 P etc. 
     
     
         8 . The anisotropic diffusion phantom according to  claim 2 , wherein the non-magnetic elements are made of glass or Teflon. 
     
     
         9 . The anisotropic diffusion phantom according to  claim 2 , wherein the non-magnetic elements are free of hydrogen nuclei.