Quantitative analysis of digital subtraction angiography using optical flow method on occlusive cerebrovascular disease

Background and purpose: Traditional digital subtraction angiography (DSA) provides detailed spatial resolution in the treatment of cerebrovascular disease. However, the available temporal information is often underutilized. The purpose of this study is to use deformable image registration with DSA to quantify the hemodynamic improvement of intracranial vessels after carotid stenting.

Materials and methods: Eighteen patients with carotid stenosis (greater than 70% degree by NASCET criteria) were treated using percutaneous transluminal angioplasty with stents. Carotid angiograms of the anterior-posterior and lateral views were acquired before and after the treatment. The arterial and venous phases of each single acquisition were classified according to the first arrival time of contrast in the distal middle cerebral artery and the superior sagittal sinus, respectively. The optical flow method was subsequently applied to determine the blood flow velocity in intracranial vessels. Blood flow velocity comparisons were performed to determine the therapeutic effects of blood flow restoration.

Results: The pixel-by-pixel blood flow velocity was estimated using the optical flow method. A color scale was used in the visualization and estimation of the blood flow velocity in the vascular bed. The improvements of blood flow velocity in both the arterial and the venous phases were significant (p<0.05). The changes with contrast agent motion were more easily observed in the arterial phase compared with the venous phases.

Conclusion: Quantitative digital subtraction angiography provides reliable blood flow velocity measurements, which facilitates pretherapeutic evaluation and a reliable follow-up analysis method for the evaluation of occlusive vascular disorder treatment in the head and neck regions.