An assessment of how the anterior cerebral artery anatomy impacts ACoA aneurysm formation based on CFD analysis

OBJECTIVE

The aim of this study was to identify independent anatomic, morphologic and hemodynamic features of the ACoA (anterior communicating artery) complex that serve as risk factors for the occurrence of ACoA aneurysms.

METHODS

Fifteen consecutive patients with 15 ACoA aneurysms were included. Computational fluid dynamics (CFD) simulations based on patient-specific models were carried out using 3D time-of-flight magnetic resonance angiography (3D-TOF-MRA) images. A reverse reconstruction technique was used to generate a pre-aneurysm vessel anatomy. Geometric parameters and hemodynamic changes were compared and evaluated.

RESULTS

The overall prevalence of symmetric, dysplastic, and absent A1 segments were 53.3%, 26.7%, and 20%. The mean wall shear stress (WSS) of the absent group (AG) was significantly higher than that of the symmetric group (SG) and dysplastic group (DG). The absolute mean A1 artery flow rate (410.2 ± 88 versus 439.4 ± 101 mL/min; p = .45) of the aneurysm side was similar between the SG and DG but significantly higher in the AG (528.1 ± 77 mL/min; p < .05). The A1-A2 angles of the aneurysm side showed no significant differences among the 3 groups (p = .32). However, the mean A1-A2 angle on the aneurysm side was smaller than the contralateral A1-A2 angle (101.9 ± 9.1˚ versus 120.3 ± 7.7˚; p <.05). A regression analysis demonstrated that high WSS was significantly associated with a large A1-A2 ratio (R2=0.52; p <.05).

CONCLUSIONS

ACoA aneurysms are a high-WSS pathology. Severe flow impingement and the anatomic vasculature structures play a role in triggering the occurrence of ACoA aneurysms.

A modified method of elastase-induced saccular aneurysm creation in rabbits: Schematic representation of the method

BACKGROUND

The purpose of our study was to investigate the safety and effectiveness of a modified technique using a short guiding catheter for instillation of elastase in comparison with the previously described method of creating elastase-induced aneurysm in rabbits.

METHODS

Following right common carotid artery (RCCA) access using an arterial sheath and inflating the Fogarty balloon in the subclavian artery, a short guiding catheter was used for the instillation of the elastase in the experimental group (n = 5) while it was performed with a microcatheter in the control group (n = 5). The procedure duration was recorded from the RCCA puncture to the sheath removal. The histological changes were characterized using H&E and Masson's trichrome (MT) staining.

RESULTS

The procedure time was 23 ± 2 min in the experimental group and 29 ± 2 min in the control group. All the rabbits (100%) in the experimental group survived without neurologic deficits, but two rabbits (40%) survived in the control group. All aneurysms were created in the saccular shape (100%) with a neck size of 2.3 ± 0.29 mm, a width of 2.75 ± 0.36 mm, and height of 6.37 ± 0.46 mm, and a dome to neck ratio of 1.21 ± 0.23. The aneurysm walls were partly thickened due to the degradation of the media tunica and adventitia proliferation with loss of the internal elastic lamina.

CONCLUSION

By using a short guiding catheter, we could instill the elastase in a more effective and safe manner in the creation of the elastase-induced aneurysm model in rabbits.

Efficacy of comparing coil behavior and distribution using the silicone aneurysm model: difference of coil distribution in the early filling stage

This study sought to establish an experimental aneurysm model of visualizing coil insertion using radiolucent nylon coils. Moreover, this study aimed to clarify the characteristics and differences of each coil and use them clinically as indices of coil selection. The coil insertion test was performed on the 10 mm spherical silicone aneurysm model filled to a nylon coil volume embolization ratio of 11.8%. Five types of coil were randomly tested six times, and the distribution of the coils was analyzed by fluoroscopy imaging. Indices of "Area (mm²)," "Feret's diameter (mm)," and "Circularity" were calculated from the fluoroscopic images. Among the indices, only "Area" showed a significant difference between coils (p = 0.002). On multivariate analysis, "Area" of the ED Infini was larger than those of Target XL soft and Galaxy G3 (p = 0.018 and 0.026, respectively). Furthermore, the area of the 360 soft was larger than that of G3 (p = 0.049). Analysis of the correlation between these values and the coil configuration showed that "Area" was negatively correlated with the stock-wire diameter (r = -0.50; p = 0.004) and primary coil configuration (r = -0.65; p < 0.001). When inserting the coils in the early stage, although the difference between each coil is relatively difficult to obtain, knowledge on the proper use of the coils with differences in characteristics can help in selecting the coil most appropriate for the conditions.

The accuracy and reliability of 3D printed aortic templates: a comprehensive three-dimensional analysis

Background

Advances in 3D printing technology allow us to continually find new medical applications. One of them is 3D printing of aortic templates to guide vascular surgeons or interventional radiologists to create fenestrations in the stent-graft surface for the implantation procedure called fenestrated endovascular aortic aneurysm repair. It is believed that the use of 3D printing significantly improves the quality of modified fenestrated stent-grafts. However, the accuracy and reliability of personalized 3D printed models of aortic templates are not well established.

Methods

Thirteen 3D printed templates of the visceral aorta and sixteen of the aortic arch and their corresponding computer tomography of angiography images were included in this accuracy study. The 3D models were scanned in the same conditions on computed tomography (CT) and evaluated by three physicians experienced in vascular CT assessment. Model and patient CT measurements were performed at key landmarks to maintain quality for stent-graft modification, including side branches and aortic diameters. CT-scanned aortic templates were segmented, aligned with sourced patient data, and evaluated for the Hausdorff matrix. Next, Bland-Altman plots determined the degree of agreement.

Results

The Intraclass Correlation Coefficients values were more than 0.9 for all measurements of aortic diameters and aortic branches diameter in all landmark locations. Therefore, the reliability of the aortic templates was considered excellent. The Bland-Altman plots analysis indicated measurement biases of 0.05 to 0.47 for aortic arch templates and 0.06 to 0.38 for reno-visceral aortic templates. The arithmetic mean of Hausdorff's mean distances of the aortic arch templates was 0.47 mm (SD =0.06) and ranged from 0.34 to 0.58. The mean metrics for abdominal models was 0.24 mm (SD =0.03) and ranged from 0.21 to 0.31.

Conclusions

The printed models of 3D aortic templates are accurate and reliable, thus can be widely used in endovascular surgery and interventional radiology departments as aortic templates to guide the physician-modified fenestrated stent-graft fabrication.

Secondary Fill Minimizes Gutter Size in Chimney EVAS Configurations In Vitro

Purpose: To investigate in an in vitro model if secondary endobag filling can reduce gutter size during chimney endovascular aneurysm sealing (chEVAS). Materials and Methods: Nellix EVAS systems were deployed in 2 silicone juxtarenal aneurysm models with suprarenal aortic diameters of 19 and 24 mm. Four configurations were tested: EVAS with 6-mm balloon-expandable (BE) or self-expanding (SE) chimney grafts (CGs) in the renal branches of both models. Balloons were inflated simultaneously in the CGs and main endografts during primary and secondary endobag filling and polymer curing. Computed tomography (CT) was performed immediately after the primary and secondary fills. Cross-sectional lumen areas were measured on the CT images to calculate gutter volumes and percent change. CG compression was calculated as the reduction in lumen surface area measured perpendicular to the central lumen line. The largest gutter volume and highest compression were presented per CG configuration per model. Results: Secondary endobag filling reduced the largest gutter volumes from 99.4 to 73.1 mm³ (13.2% change) and 84.2 to 72.0 mm³ (27.6% change) in the BECG configurations and from 67.2 to 44.0 mm³ (34.5% change) and 92.7 to 82.3 mm³ (11.2% change) in the SECG configurations in the 19- and 24-mm models, respectively. Secondary endobag filling increased CG compression in 6 of 8 configurations. BECG compression changed by −0.2% and 5.4% and by −1.0% and 0.4% in the 19- and 24-mm models, respectively. SECG compression changed by 10.2% and 16.0% and by 7.2% and 7.3% in the 19- and 24-mm models, respectively. Conclusion: Secondary endobag filling reduced paragraft gutters; however, this technique did not obliterate them. Increased CG compression and prolonged renal ischemia time should be considered if secondary endobag filling is used.

Surgical options in experimental porcine model for endovascular training in complex vascular lesions

We describe a new, elegant, two-phase, microsurgical method that minimizes the surgical preparation time for different complex vascular lesions in a swine model. In the first phase, the model is prepared microsurgically in the experimental laboratory using arterial or/and venous grafts. In the second phase, the model is implanted in the experimental animal. This two-fold method allows for increasing the complexity and accuracy of the model while reducing preparation time on the day of the training session.

A Modified Method for Creating Elastase-Induced Aneurysms by Ligation of Common Carotid Arteries in Rabbits and Its Effect on Surrounding Arteries

BACKGROUND AND PURPOSE

Rabbit models of intracranial aneurysms are frequently used in pre-clinical settings. This study aimed to demonstrate an alternative, extravascular method for creating elastase-induced aneurysms, and how ligation of the right common carotid arteries (RCCA) can impact flow redistribution into left CCA (LCCA).

METHODS

Elastase-induced aneurysms in 18 New Zealand rabbits (4.14 ± 0.314 kg) were created by applying 3-5 U of concentrated elastase solution to the exterior of the right and left CCA roots (RCCA and LCCA). After the induction of the aneurysm, the aneurysm was either kept intact to the rest of the corresponding CCA, severed from the rest of the CCA to allow for a free standing aneurysm, or was anchored to nearby tissue to influence the angle and orientation of the aneurysm with respect to the parent vessel. Ultrasound studies were performed before and after creation of aneurysms to collect blood flow measurements inside the aneurysm pouch and surrounding arteries. Prior to sacrificing the animals, computed tomography angiography studies were performed. Harvested aneurysmal tissues were used for histological analysis.

RESULTS

Elastase-induced aneurysms were successfully created by the extravascular approach. Histological studies showed that the biological response was similar to human cerebral aneurysms and previously published elastase-induced rabbit aneurysm models. Ultrasound measurements indicated that after the RCCA was ligated, blood flow significantly increased in the LCCA at one-month follow-up.

CONCLUSION

An alternate method for creating elastase-induced aneurysms has been demonstrated. The novel aspects of our method allow for ligation of one or both common carotid arteries to create a single or bilateral aneurysm with an ability to control the orientation of the induced aneurysm.