Long-term follow-up of Intracranial Aneurysms facilitated by three-dimensional reconstruction of DSA and MRA Imaging

Introduction: The long-term follow-up of treated cerebral aneurysms is mostly performed analyzing 2D images. The objective of the present study was to evaluate 3D-visualisation techniques for quantification and classification of regrowth patterns of treated aneurysms.

Methods: Retrospective analyses of 20 patients was performed that were treated for intracerebral aneurysms by either neurosurgical clipping or endovascular coiling. The patients had a median imaging follow-up of 6 years including rotational digital subtraction angiography (rDSA) or magnetic resonance angiography (MRA) imaging. The volume data sets were coregistered and visualized using the Amira software system. The remaining or recurring aneurysms were analysed with regards to their growth pattern and the volume.

Volumetric quantification was performed after coregistration of data sets and subsequent subtraction between different time points to demonstrate a time dependent shrinkage or growth.

Results: After import and coregistration, the vessels were segmented and various analyses ensued, including calculation of the relative surface area of the parent vessel related to the aneurysmal surface, resulting reconstructed vessel surface, volume of remnant or new aneurysm, vascular caliber measurements, principal direction of blood stream. Comparison of three-dimensional reconstruction of cerebral aneurysms including overlay and subtraction improved detection of subtle changes in aneurysm size and configuration over time. Growth patterns were classified according to compaction and circumferential regrowth (coiling only), neck enlargement, paralesional enlargement.

Conclusion: The selected series of treated aneurysms does not allow to quantify the risk for recurrence but demonstrates new tools for processing of complex 3D vascular data. This type of visualization provide valuable time-dependent changes that are more difficult to extract from 2D slices. Further analysis includes the calculation of vascular shear stress around the treated aneurysm to generate algorithms that might help to find lesions at risk for recurrence.