Experimental investigation of intravascular OCT for imaging of intracranial aneurysms

Rupture risk assessment of an intracranial aneurysm (IA) is an important factor for indication of therapy. Until today, there is no suitable objective prediction method. Conventional imaging modalities cannot assess the IA's vessel wall. We investigated the ability of intravascular optical coherence tomography (OCT) as a new tool for the characterization and evaluation of IAs. An experimental setup for acquisition of geometrical aneurysm parameters was developed. Object of basic investigation was a silicone phantom with six IAs from patient data. For structural information, three circle of Willis were dissected and imaged postmortem. All image data were postprocessed by medical imaging software. Geometrical image data of a phantom with six different IAs were acquired. The geometrical image data showed a signal loss, e.g., in aneurysms with a high bottleneck ratio. Imaging data of vessel specimens were evaluated with respect to structural information that is valuable for the characterization of IAs. Those included thin structures (intimal flaps), changes of the vessel wall morphology (intimal thickening, layers), adjacent vessels, small vessel outlets, arterial branches and histological information. Intravascular OCT provides new possibilities for diagnosis and rupture assessment of IAs. However, currently used imaging system parameters have to be adapted and new catheter techniques have to be developed for a complete assessment of the morphology of IAs.