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measurements of both intrapedicular and intravenous pressure would have been more useful, since this would have provided a better estimate of the net ΔP across the AVM nidus. Furthermore, the simultaneous measurement of either volumetric blood flow or blood-flow velocities would have been invaluable in further defining the flow conditions of a given system. Without these measurements, we are unable to adequately speculate about the etiology of differences in intrapedicular pressures observed in this study. For example, it is difficult to know if the relative elevation of

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Satoshi Tateshima, Yuichi Murayama, J. Pablo Villablanca, Taku Morino, Hikoichiro Takahashi, Takatsugu Yamauchi, Kazuo Tanishita and Fernando Viñuela

Object. To obtain precise flow profiles in patients' aneurysms, the authors developed a new in vitro study method featuring an aneurysm model manufactured using three-dimensional computerized tomography (3D CT) angiography.

Methods. A clear acrylic basilar artery (BA) tip aneurysm model manufactured from a patient's 3D CT angiogram was used to analyze flow modifications during one cardiac cycle. Stereolithography was utilized to create the aneurysm model. Three-dimensional flow profiles within the aneurysm model were obtained from velocity measurements by using laser Doppler velocimetry. The aneurysm inflow/outflow zones changed dynamically in their location, size of their cross-sectional area, and also in their shapes over one cardiac cycle. The flow velocity at the inflow zone was 16.8 to 81.9% of the highest axial velocity in the BA with a pulsatility index (PI) of 1.1. The flow velocity at the outflow zone was 16.8 to 34.3% of the highest axial velocity of the BA, with a PI of 0.68. The shear stress along the walls of the aneurysm was calculated from the fluid velocity measured at a distance of 0.5 mm from the wall. The highest value of shear stress was observed at the bleb of the aneurysm.

Conclusions. This clear acrylic model of a BA tip aneurysm manufactured using a CT angiogram allowed qualitative and quantitative analysis of its flow during a cardiac cycle. Accumulated knowledge from this type of study may reveal pertinent information about aneurysmal flow dynamics that will help practitioners understand the relationship among anatomy, flow dynamics, and the natural history of aneurysms.

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Satoshi Tateshima, Fernando Viñuela, J. Pablo Villablanca, Yuichi Murayama, Taku Morino, Kiyoe Nomura and Kazuo Tanishita

was noted at the center of the lesion, dividing two outflow zones located at the distal and proximal areas of the orifice. The inflow zone moved to the distal and medial aspects of the aneurysm opening and became smaller in size during the early systolic phase. There was no appreciable change in the shape of the inflow zone between the early systolic and peak systolic phases, but blood flow velocity rapidly increased. The inflow zone moved to the distal area of the orifice during the early diastolic phase. Another small inflow zone was formed at the proximal lateral

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Satoshi Tateshima, John Grinstead, Shantanu Sinha, Yih-Lin Nien, Yuichi Murayama, J. Pablo Villablanca, Kazuo Tanishita and Fernando Viñuela

. 2, 5–7, 24 The phase-contrast MR imaging procedure has already been used in a clinical setting to visualize in vivo fluid motions such as cerebrospinal fluid flow in the cisterns and ventricular systems. 7, 16, 23 Blood flow velocity in the intracranial arteries can be measured using the phase-contrast MR imaging procedure. 7, 9 This technique appears to be feasible for visualizing complex 3D flow structures in large vessels with the use of phase-contrast MR imaging. 11, 12 It has been a challenge to visualize complex 3D flow structures in cerebral aneurysms

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Prem Venugopal, Daniel Valentino, Holger Schmitt, J. Pablo Villablanca, Fernando Viñuela and Gary Duckwiler

include the implicit assumption that the flow rate in the patient may not be very different from that in a healthy volunteer. Nevertheless, there could be substantial interindividual variability in intracranial artery blood flow velocities. For example, in a group of 62 women, Hart and Haluszkiewicz 9 found, using TCD ultrasonography, that the mean blood flow velocity in the middle cerebral artery could be anywhere between 41.4 cm/second and 71.4 cm/second. Similar interindividual variations in blood flow velocity have been noted in the ACA, 9 the internal carotid