Time-resolved 3D rotational angiography: display of detailed neurovascular anatomy in patients with intracranial vascular malformations
The purpose of this pilot study was to demonstrate the applicability of time-resolved three-dimensional (3D) reconstructions from 3D digital subtraction angiography (DSA) rotational angiography (RA) datasets (four-dimensional (4D) DSA) to provide a more detailed display of the architecture of intracranial vascular malformations.Methods
The experimental reconstruction software was applied to the existing 3D DSA datasets obtained with Siemens Artis zee biplane neuroangiography equipment. We included 27 patients with clinical indications for 3DRA for preinterventional or preoperative evaluation of intracranial dural arteriovenous fistulas (dAVFs, n=8) or arteriovenous malformations (AVMs, n=19). A modified DSA acquisition protocol covering an extended rotation angle of the C-arm of 260° during a scan time of 12 s was used. 4D volumes were displayed with up to 30 frames/s in a transparent volume rendering (VRT) mode and time-resolved multiplanar reconstructions (MPRs). Arterial feeders, fistulous points, or the shunt zone within the AVM nidus and venous drainage patterns as well as associated aneurysms were assessed after definition of a standardized evaluation procedure by consensus of two reviewers in comparison with 2D DSA and conventional 3D reconstructions.Results
In all cases calculation of 4D reconstructions were technically feasible and evaluable. In two cases image quality was slightly compromised by movement artifacts. Compared with standard DSA projection images and 3D reconstructions, 4D VRTs and MPRs were rated significantly superior to define a proper projection and display of the shunt zone. In 12 out of 27 cases 4D reconstructions showed details of the angioarchitecture at the fistulous point or the nidus better than the other modalities and came close to the quality of superselective angiography. The efficacy of 3D and 4D applications was equal in the detection of pre- and intranidal aneurysms. The course of long arterial feeders and draining veins was difficult to assess on VRTs and MPRs. Especially for dAVFs, 2D DSA was clearly superior in identifying meningeal feeders. For detecting smaller vessels and for distinction between angiographic phases, 2D DSA is still considered to be superior to 4D imaging. Venous drainage was slightly better displayed in 4D reconstructions.Conclusions
Time-resolved 3DRA with 4D VRTs and MPRs is technically feasible and provides a detailed display of the angioarchitecture at the fistulous point or the nidus. Visualization of all angiographic features demands additional post-processing. Further standardization of evaluation tools and studies with blinded independent reviewers are necessary before the new technique can replace conventional neuroangiographic approaches.