gms | German Medical Science

Objective: Intraoperative magnetic resonance imaging (iMRI) was shown to optimize the extent of resection (EOR) of parenchymal brain tumors and is therefore increasingly used all over the globe. Yet, while preoperative MRI-based treatment plans contain additional functional information such as tractography, additional recording of diffusion imaging for intraoperative tractography is frequently limited by the MRI scanner and available time. To facilitate the use of elaborate preoperative treatment plans after an intraoperative navigation update via iMRI, an elastic image fusion (EIF) algorithm was developed, which enables spatial alignment of preoperative data with respect to the intraoperative images and its physical deformation. This study was therefore designed to evaluate the gain in accuracy by using EIF compared to standard rigid fusion.

Methods: Ten MRI-iMRI data pairs (3D T1-weighted) were evaluated and typical anatomical landmarks, such as vessel bifurcations, were assessed in both hemispheres. The preoperative and intraoperative MRI scans were elastically fused by using a prototype EIF software (Brainlab AG, Munich). For each landmark pair, the Euclidean distance was calculated for rigidly and elastically fused image data.

Results: In all patients, typical predefined anatomical landmarks could be endorsed in pre- and intraoperative MRI. The Euclidean distance, between specific landmarks, was 2.66 ± 2.64 mm using standard rigid fusion and 1.85 ± 1.57 mm using our EIF algorithm (p<0.01). For landmarks near the resected lesion, which were subject to higher anatomical distortion due to the nearby resection cavity, the Euclidian distances were 4.36 ± 3.36 mm and 2.60 ± 1.90 mm, respectively (p<0.01).

Conclusion: Our data show that EIF can compensate for surgery-related brain shift and our approach is able to quantify the accuracy of this newly-evolved algorithm. The establishment of an easy applicable and reliable EIF tool integrated in the clinical workflow, e.g. by updating preoperative planning content, such as fiber tractography, could open a large variety of new options for image-guided tumor surgery.