Update of diagnostic preoperative images using low-field interventional MRI for navigation in neurosurgery: rigid-body registration

摘要

This study looks into the rigid-body registration of pre-operative anatomical high field and interventional lowfield magnetic resonance images (MRI) . The accurate 3D registration of these modalities is required to enhancethe content of interventional images with anatomical (CT, high field MRI, DTI), functional (DWI, fMRI, PWI),metabolic (PET) or angiography (CTA, MRA) pre-operative images. The specific design of the interventionalMRI scanner used in the present study, a PoleStar N20, induces image artifacts, such as ellipsoidal maskingand intensity inhomogeneities, which affect registration performance. On MRI data from eleven patients, whounderwent resection of a brain tumor, we quantitatively evaluated the effects of artifacts in the image registrationprocess based on a normalized mutual information (NMI) metric criterion. The results show that the quality ofalignment of pre-operative anatomical and interventional images strongly depends on pre-processing carried outprior to registration. The registration results scored the highest in visual evaluation only if intensity variationsand masking were considered in image registration. We conclude that the alignment of anatomical high fieldMRI and PoleStar interventional images is the most accurate when the PoleStar's induced image artifacts arecorrected for before registration.