A high-resolution phantom for MRI

Assessment of spatial resolution is an important step to test the performan ce of new sequence techniques-especially ultrafast techniques with dedicate d k-space trajectories or interpolation algorithms. Measurement of the modu lation transfer function (MTF) is a rather difficult procedure, but using s uitable resolution phantoms allows a simple visual evaluation of spatial re solution. In contrast to commonly used test objects with a very restricted number of resolution patterns we developed a phantom containing resolution patterns f rom 0.1 to 1.5 mm in steps of 0.1 mm. One resolution pattern consists of fi ve parallel Plexiglas strips with the distance of the strips being equal to their thickness. Together with a Plexiglas cuboid the resolution patterns are mounted on a Plexiglas plate on the bottom of the cylindrical phantom. An aqueous solution of manganese chloride is used to fill the phantom. High resolution cross sections (pixel size: 50 mum) through the resolution patt erns were measured to confirm the correct dimensions of the phantom. To ver ify the appropriateness of the 0.1 and 0.2 mm stacks micro-CT images with a pixel size of 25 mum were acquired additionally for both patterns. Besides visual inspection evaluation of the profile function of signal intensity a cross the stacks demonstrates that the resolution patterns are sufficiently correct. T-1-weighted SE sequences with slightly different pixel sizes as well as T-1- and T-2-weighted gradient echo sequences were applied to demon strate some possible applications of this phantom. In conclusion, the propo sed phantom is well suited to assess the spatial resolution qualitatively ( i.e., visually) and quantitatively over a wide range in steps of 0.1 mm. (C ) 2001 Elsevier Science Inc. All rights reserved.