Intra-aneurysmal flow patterns: illustrative comparison among digital subtraction angiography, optical flow, and computational fluid dynamics.

BACKGROUND AND PURPOSE: Digital subtraction angiography is the gold standard vascular imaging and it is used for all endovascular treatment of intracranial anerysms. Optical flow imaging has been described as a potential method to evaluate cerebral hemodynamics through DSA. In this study, we aimed to compare the flow patterns measured during angiography, by using an optical flow method, with those measured by using computational fluid dynamics in intracranial aneurysms. MATERIALS AND METHODS: A consecutive series of 21 patients harboring unruptured saccular intracranial aneurysms who underwent diagnostic angiography before treatment was considered. High-frame-rate digital subtraction angiography was performed to obtain an intra-aneurysmal velocity field by following the cardiac-modulated contrast wave through the vascular structures by using optical flow principles. Additionally, computational fluid dynamics modeling was performed for every case by using patient-specific inlet-boundary conditions measured with the optical flow method from both DSA and 3D rotational angiography datasets. Three independent observers compared qualitatively both the inflow direction and the apparent recirculation in regular DSA, optical flow images, and computational fluid dynamics flow patterns for each patient; κ statistics were estimated. RESULTS: We included 21 patients. In 14 of these 21, the flow patterns were conclusive and matching between the optical flow images and computational fluid dynamics within the same projection view (κ = .91). However, in only 8 of these 14 patients the optical flow images were conclusive and matching regular DSA images (observer κ = 0.87). In 7 of the 21 patients, the flow patterns in the optical flow images were inconclusive, possibly due to improper projection angles. CONCLUSIONS: The DSA-based optical flow technique was considered qualitatively consistent with computational fluid dynamics outcomes in evaluating intra-aneurysmal inflow direction and apparent recirculation. Moreover, the optical flow technique may provide the premises for new solutions for improving the visibility of flow patterns when contrast motion in DSA is not apparent. This technique is a diagnostic method to evaluate intra-aneurysmal flow patterns and could be used in the future for validation and patient evaluation.

Transjugular intrahepatic portosystemic shunt stent-graft placement: mean optimal portal venous projection view determined by three-dimensional portography.

BACKGROUND: Suboptimal stent-graft placement at the lower anastomosis during transjugular intrahepatic portosystemic shunt (TIPS) may result in early shunt stenosis and occlusion owing to incomplete covering of the parenchymal tract by the covered part of the stent-graft. PURPOSE: To determine the optimal portal venous projection view for stent-graft placement during TIPS and the potential influence of the portal vein anatomy. MATERIAL AND METHODS: On 76 cirrhotic patients (48 men and 28 women) selected for TIPS, rotational, three-dimensional (3D), catheter-directed angiography of the portal vein was performed. The 3D portograms were reviewed by two independent interventional radiologists to determine the optimal angiographic projection views for stent-graft placement. Intra-observer and inter-observer reliabilities were tested and subgroups of patient portal vein anatomy were categorized. RESULTS: Among all patients, the optimal portal venous projection views for stent-graft placement during TIPS centered around 27° (±14°) right oblique and 3° (±7°) craniocaudal. Of these, 56% were within the standard deviations. Intra-observer reliabilities were 0.60 and 0.62 for the two radiologists, respectively. Inter-observer reliability was 0.48. Anatomical variations in the patient population were: normal portal vein (67%), trifurcation at main portal vein (16%), right posterior portal vein as the first branch of main portal vein (3%), no right posterior portal vein (1%), and other variations (13%). Anatomical subgroups did not influence the best angiographic projection view significantly (F4,295 = 0.91, P = 0.457). CONCLUSION: The mean optimal angiographic projection view for TIPS stent-graft placement was 27° right oblique and 3° craniocaudal. Patient anatomic variations do not play a significant role in determining the optimal angiographic view for TIPS stent-graft placement.