Localization Technique for Frameless Image-guided Robotic Radiosurgery of Arteriovenous Malformations

Abstract

Purpose/Objective(s): To integrate three-dimensional digital rotation angiography (3D DRA) and two-dimensional digital subtraction angiography (2D DSA) imaging in a localization technique that enables frameless image-guided robotic radiosurgery of arteriovenous malformations (AVMs). Materials/Methods: The geometric integrity of the 3D DRA images generated by a clinical flat panel detector Carm neuroangiography system was evaluated and quantified by imaging a phantom with embedded markers. Dedicated DSA acquisition modes with preset C-arm positions were configured. The geometric reproducibility of the C-arm presets was investigated and its impact on localization accuracy evaluated. An imaging protocol comprising anterior-posterior (AP) and lateral (LAT) 2D DSA series combined with 3D DRA without couch displacement between acquisitions was introduced. A software environment (Angio-Localize) was developed for 2D-3D registration of the 3D DRA and the 2D DSA images to correct for: (i) small misalignments of the C-arm with respect to the assumed geometry of the preset imaging positions and (ii) potential patient motion between the image series. Within the same environment, correlated navigation of the registered 3D DRA and DSA images was incorporated so that an AVM could be localized and contoured within the 3D DRA coordinate space. AVM contours were then transferred onto a planning CT by CT-3D DRA registration. The subsequent treatment planning and delivery followed the standard process for frameless image-guided robotic radiosurgery treatments. Results: The magnitude of the 3D DRA spatial distortions was smaller than 0.3 mm throughout a 140 mm x 140 mm x 140 mm field of view. Localization uncertainties resulting from the achievable reproducibility of the C-arm preset positions were reduced to less than 0.2 mm with 3D-2D image registration. Overall system-related localization uncertainty within the DRA coordinate space was estimated to be 0.4-0.5 mm. The localization protocol was implemented clinically and image-guided frameless robotic radiosurgical treatments with this technique were initiated. Conclusions:The integration of three-dimensional digital rotation angiography (3D DRA) and two-dimensional digital subtraction angiography (2D DSA) imaging in a localization technique that enables frameless image-guided robotic radiosurgery of arteriovenous malformations (AVMs) is possible. Clinically it is expected to result in increased patient comfort; reduced time pressure on clinical and technical staff, and possible reduction of the number of neuro-angiography procedures for particular patient.