Ahead of Print: Distortion Correction for Stereotactic MR

Background: Image distortion limits direct 3T MR image application for stereotactic functional neurosurgery.

Objective: To test the application of a method to correct and curtail image distortion for 3T MR images.

Methods: We used a phantom head model mounted on a platform with the dimensions and features of a stereotactic frame. The phantom was scanned within the head coil of a Philips Achieva 3T X series (TM). For each scan, 2 images were obtained-the normal and the reversed image (nMR and rMR, respectively). We applied the inverted gradient correction protocol to produce a corrected x, y and z coordinate. We applied the Cronbach test or coefficient of reliability to assess the internal consistency of the data.

Results: For all analyzed data, the P value was above .05, indicating that the differences among the observers were not statistically significant. Moreover, the data rectification proved to be effective, as the average distortion after correction was 1.05 mm. The distortion varied between 0.7 mm and 3.7 mm, depending on the target location.

Conclusion: This study examined a rectifying technique for correcting geometric distortions encountered in the MR images related to static field inhomogeneities (resonance offsets), and the technique proved to be highly successful in producing consistently accurate stereotactic target registration. The technique is applicable to all routinely employed spin-echo MR images.

From: An Image Correction Protocol to Reduce Distortion for 3T Stereotactic MRI by Tavares et al.

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