Intracranial aneurysms: in vitro study of “intracranial” pressure and parent vessel curvature as potential modifiers of aneurysm pulsation amplitude

Intracranial aneurysms: in vitro study of “intracranial” pressure and parent vessel curvature as potential modifiers of aneurysm pulsation amplitude | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Intracranial aneurysms: in vitro study of “intracranial” pressure and parent vessel curvature as potential modifiers of aneurysm pulsation amplitude Axel E. Vanrossomme, Kamil J. Chodzyński, Robert Tropsek, Simon Henkes, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8211535/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Although aneurysm pulsation – or wall motion – has been studied as a potential criterion to identify aneurysms prone to rupture, factors affecting this pulsation are not well understood. The purpose of this study was to test in vitro whether external – “intracranial” – pressure and/or parent vessel curvature impacted aneurysm pulsation and how. In this study, time-resolved CT angiography was used to detect and quantify volume pulsation of silicon aneurysm models using a test bench that could reproduce pulsatile flow within these models. A hermetic pressure box allowed us to test a range of external pressure on a simplified straight aneurysm model. For the second part, four silicon aneurysm models were custom made with varying curve radiuses at the aneurysm neck. Results show that in a simplified in vitro setting an increase in external – “intracranial” – pressure leads to a decrease in pulsation amplitude and vice versa, and that the parent vessel curvature is not correlated with pulsation amplitude. Health sciences/Diseases Physical sciences/Engineering Health sciences/Medical research Health sciences/Neurology Biological sciences/Neuroscience Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Intracranial aneurysm pulsation – or wall motion – has been proposed as a potential criterion to identify aneurysms that are more likely to rupture, and to rupture sooner [ 1 – 4 ]. Although several imaging techniques have been used to detect and quantify aneurysm pulsation [ 5 ], factors that might affect aneurysm pulsation and its measurement have not been identified. Wardlaw et al hypothesized that intracranial pressure could modulate the amplitude of pulsation by increasing or decreasing tensile forces in the aneurysm wall. According to these authors, an decrease in intracranial pressure leads to an increase in aneurysm volume. The increase in volume increases the tensile forces in the wall which could reduce wall motion. This could explain why neurosurgeons usually do not detect aneurysm pulsation during surgery [ 6 ]. This hypothesis however was not properly tested. Similarly, parent vessel curvature is known to modify the intra-aneurysmal fluid dynamics as studied both by computational fluid dynamics and 4D-flow magnetic resonance imaging [ 7 – 10 ]. However, the impact of this parameter on aneurysm pulsation is not clear and has not, to our knowledge, been formally tested. Therefore, the aim of our study has been to test in an in vitro setting whether external – “intracranial” – pressure or parent vessel curvature had a detectable impact on the aneurysm pulsation, and how it impacted it. Materials and methods Acquisitions were made out on a 64 detector-rows CT scanner (Somatom Definition AS, Siemens Healthineers, Erlanger, Germany) equipped with a z-flying focal spot X-ray tube (Straton, Siemens). All acquisitions were done with a stationary table using the following parameters: peak kilovoltage = 120 kVp; time-current product = 190 mAs; acquisition scan time = 5 s; tube rotation time = 0.3 s. Each acquisition was reconstructed as a series of volumes each containing 64 slices with a nominal thickness of 0,6 mm with a time interval of 50 ms between each successive volume. This resulted in 94 volumes per acquisition. Both parts of this study were carried out using a test bench that could apply reproducible pulsatile flow to silicon aneurysm phantoms (European patent reference EP2779144—Fig. 1 ). The circuit was filled with a glycerine and water solution, the viscosity of which was similar to the average human blood viscosity (3.45 x 10 − 3 Pa.s at 20°C). Iopromide 370 mgI/ml (Ultravist, Bayer HealthCare, Leverkusen, Germany) was then added to the aforementioned solution at a ratio of 1:4 in order to achieve sufficient opacification. The centrifugal pump was adjusted to generate a mean flow of 180 ml/min. Piston pump frequency was set at 1.5 Hz and pulse pressure was gradually increased as detailed below. The mean pressure in the circuit was maintained at 90 mmHg using valves. Pulsation was defined as the difference between the highest and lowest volume of each pulse cycle. Average volume pulsation and standard deviations were calculated for each experiment. All pressure values are to be understood as taking atmospheric pressure as reference (0 mmHg). Part 1 – Intracranial pressure and pulsation To mimic intracranial pressure, a spherical silicon aneurysm phantom on a straight silicon tube connected to the test bench described above was put inside a sealed pressure chamber. This chamber consisted of a poly(methyl methacrylate) box equipped with a manometric valve. Pressure inside that box – later referred to as “external pressure” – was set at 0 mmHg, 12.5 mmHg, 25 mmHg, 50 mmHg, and 70 mmHg. For each value of external pressure, piston pump voltage was set at 0 V, 1 V, 1.5 V, 2 V, and 2.5 V for the first two repetition of the experiment, generating pulse pressures of approximately 0 mmHg, 70 mmHg, 115 mmHg, 190 mmHg and 270 mmHg respectively. The pulse pressures were measured during the experiment and recorded. 4D-CTA acquisitions were made for each combination of external pressure and pulse pressure. Part 2 – Parent vessel curvature and pulsation Four different models of silicon aneurysm (Fig. 2 ) were custom made by Elastrat (Geneva, Switzerland). The radius of curvature (RC) of the silicon tube at the aneurysm neck was 10 mm, 20 mm and 30 mm in the first three models. The last one was straight. The tubes were stabilized using 3D printed guides, to ensure there would be no variation of curvature during the acquisitions or between the repetitions. For each value of external pressure, piston pump voltage was set at 0 V, 1 V, 1.5 V, 2 V, and 2.5 V generating pulse pressures of approximately 0 mmHg, 70 mmHg, 115 mmHg, 190 mmHg and 270 mmHg respectively. The pulse pressures were measured during the experiment and recorded. 4D-CTA acquisitions were made for each combination of curvature – defined as 1/RC – and pulse pressure. The whole set of experiments was repeated 3 times to ensure that the findings were reproducible. In addition to this, computational fluid dynamics was used to determine velocity magnitude maps inside the aneurysm models. Image post-processing and analysis Pulsation analysis was performed using a semi-automated method that was developed in the lab, using MATLAB 2015b software (MathWorks, Natcick, MA) with additional toolboxes (Parallel Computing Toolbox 6.7 and Image Processing Toolbox 9.3). DICOM imaged were organized as a three-dimensional matrix where X and Y units were the pixel size and Z unit was the slice thickness. “Imwarp” MATLAB function was used to perform a linear interpolation to obtain isotropic voxels with a nominal size equal to that of the original X-Y pixels. The grey scale matrix was converted to a black-and-white matrix using a Hounsfield Unit threshold that was defined visually for each acquisition by a radiologist with more than 10 years of expertise in cardiovascular imaging, in order to best fit the aneurysm. All voxels with an attenuation value that was higher than the defined threshold were given a value of 1, those lower than the threshold a value of 0. Masks were then applied to the resulting 3D matrix to remove the tube and extract only the aneurysm. The first mask was applied to extract a smaller region of interest containing the aneurysm to remove any potential close object and to reduce calculation time, using “imcrop” MATLAB function. The second mask was an XY elliptic mask applied manually on the tube on one image using “imellipse” MATLAB function, to remove the tube and the contrast medium within it. As the tubes were not all straight, the position of this mask was corrected automatically using an algorithm that followed the center of the tube on each 2D image. The resulting matrix contained only voxels from the aneurysm with a value of 1, all the other voxels being replaced by 0. To calculate the volume of the aneurysm sac, the following equation was used: Volume (mm³) = N V1 x X V x Y V x Z V with N V1 = the total number of voxels with a value of 1 X V , Y V and Z V = the size of each voxel in the X, Y and Z directions respectively Pulsation amplitude was calculated as follows: AVP (%) = 100 x (AV max – AV min ) / AV mean with AVP = aneurysm volume pulsation or pulsation amplitude AV max , AV min and AV mean = maximum, minimum and mean aneurysm volume This whole process was repeated for each time step. Statistics Sigmaplot12 software was used. Comparisons were done using One-Way ANOVA. Normality was calculated by using the Shapiro-Wilk's test. A probability level of p < 0.05 was considered as statistically significant. Results Part 1 – Intracranial pressure and pulsation The relation between pulsation and external pressure was linear in the range that was tested. The average volume amplitude of all three repetition with standard deviations are summarized in Table 1. EP (mmHg) PP ± SD (mmHg) AAV ± SD (mm 3 ) APA ± SD (mm 3 ) 0 0 ± 0 532 ± 11 0.24 ± 0.09 12.5 0 ± 0 537 ± 20 0.36 ± 0.22 25 0 ± 0 541 ± 20 0.25 ± 0.13 50 0 ± 0 530 ± 15 0.26 ± 0.11 70 0 ± 0 518 ± 11 0.27 ± 0.12 0 69.4 ± 1.5 536 ± 7 8.51 ± 0.95 12.5 69.4 ± 1.5 525 ± 5 8.07 ± 0.80 25 69.4 ± 1.5 535 ± 21 7.80 ± 1.27 50 69.4 ± 1.5 528 ± 24 7.36 ± 0.91 70 69.4 ± 1.5 523 ± 5 6.98 ± 0.71 0 112.4 ± 5.5 536 ± 6 14.03 ± 2.01 12.5 112.4 ± 5.5 532 ± 9 13.22 ± 2.06 25 112.4 ± 5.5 530 ± 12 12.97 ± 2.32 50 112.4 ± 5.5 528 ± 13 12.37 ± 1.55 70 112.4 ± 5.5 522 ± 10 12.04 ± 2.39 0 186.6 ± 8.4 537 ± 16 22.70 ± 3.68 12.5 186.6 ± 8.4 542 ± 20 22.73 ± 4.27 25 186.6 ± 8.4 533 ± 13 21.79 ± 2.68 50 186.6 ± 8.4 531 ± 12 21.15 ± 3.29 70 186.6 ± 8.4 257 ± 13 20.41 ± 2.99 0 267.8 ± 9.1 540 ± 13 35.41 ± 4.13 12.5 267.8 ± 9.1 530 ± 13 33.88 ± 2.77 25 267.8 ± 9.1 535 ± 11 32.02 ± 5.79 50 267.8 ± 9.1 532 ± 13 31.17 ± 4.93 70 267.8 ± 9.1 531 ± 14 30.06 ± 5.12 EP : external pressure ; PP : pulse pressure ; SD : standard deviation ; AAV : average aneurysm volume ; APA : average pulsation amplitude. Results show that for each non-null value of pulse pressure, pulsation decreased with increasing external pressure (Fig. 3 ). PP: pulse pressure; APA: average pulsation amplitude ; EP : external pressure Additionally the average volume of the aneurysm decreased by 2 to 3% between 0 and 70 mmHg of external pressure (Fig. 5 ). AAV: average aneurysm volume; EP: external pressure Part 2 – Parent vessel curvature and pulsation Results of the three repetitions are summarized in Table 2. Relative pulsation amplitude (%) PP (mmHg) Str R10 R20 R30 Str vs R10 vs R20 vs R30 Str vs R20 vs R30 R1 R2 R3 R1 R2 R3 R1 R2 R3 R1 R2 R3 p p 0 0.23 0.19 0.18 0.17 0.23 0.20 0.22 0.24 0.32 0.23 0.37 0.30 0.08 0.12 70 3.75 3.28 3.13 2.86 2.45 2.66 3.41 3.32 3.26 3.65 3.44 3.30 0.01 0.75 115 5.78 5.27 5.05 4.34 3.85 4.60 5.09 4.72 6.18 6.23 5.08 5.59 0.06 0.79 190 9.20 7.77 8.10 7.32 6.15 7.32 8.45 7.32 9.32 10.14 8.46 8.86 0.06 0.48 270 13.30 11.31 11.50 10.47 9.37 10.75 12.07 10.71 12.76 14.29 11.28 12.47 0.12 0.70 Str : straight model ; R10, R20, R30 : models with a 10 mm, 20 mm or 30 radius of curvature respectively ; PP : pulse pressure. Comparisons were done using One-Way ANOVA. A probability level of p < 0.05 was considered as statistically significant. Taking all models into consideration, there was no significant different between pulsation amplitudes except at 70 mmHg. However, further investigation showed that the silicon of the 10 mm-RC aneurysm was thicker and less compliant than the other three : the models volume was quantify for different values of internal pressure, in the absence of pulsation, and the relative variation compared to 0 mmHg interior pressure (over atmospheric pressure) was calculated for each model (Fig. 6 ). Normalizing the compliance of each model to the smallest one (10mm-RC), normalized deformation coefficient were quantified as follows: 1 for the 10 mm-RC model; 2.01 for the 20mm-RC model ; 2.23 for the 30mm-RC model and 1.81 for the straight model. As the compliance of the 10 mm-RC model was approximately half of the compliance of the other models, it was decided to exclude 10 mm-RC model as it induced a significant bias. Excluding the data from the 10 mm-RC model, there was no significant difference between pulsation amplitudes of straight, 20 mm-RC and 30 mm-RC aneurysm models. Computational fluid dynamic analysis however shows different velocity and pressure maps with an increase in inflow jet velocity and a slight increase in intra-aneurysmal pressure with increasing curvature (Fig. 7 ). Discussion Our results show that 1) contrary to what had been hypothesized before, in an in vitro setting, an increase in external pressure reduces the amplitude of pulsation of the aneurysm model, although the total volume of the aneurysm decreases; 2) tube curve radius does not seem to impact pulsation amplitude. In our simplified in vitro setting, an increase in external pressure led to a decrease in total aneurysm volume but that was not accompanied by an increase in pulsation amplitude as had been hypothesized by Wardlaw [ 6 ]. An increase in external pressure actually reduced wall motion. If wall tensile forces are obviously a crucial determinant of pulsation amplitude, the importance of its variation was probably overestimated. Tensile forces are proportional to \(\:\sqrt{r}\) . As we mentioned above, the variation in aneurysm volume between 0 and 70 mmHg of external pressure was only 2 to 3%. The resulting variation in tensile forces would therefore be negligible compared to the effect of external pressure opposing the outward expansion of the aneurysm, which is proportional to the external pressure. What could therefore explain the absence of visible pulsation during surgery? Our hypothesis is a combination of three factors. Firstly, even though a decrease in external pressure was associated with an increase in pulsation amplitude, the effect was very small for the normal range of arterial pulse pressure – 30 to 60 mmHg – and intracranial pressure – 0 to 15 mmHg if we consider open neurosurgery within the range. Secondly, the human eye is not very effective at detecting motions of very small amplitude. The usually admitted angular resolution of the human eye is approximately 1 arcminute which translate to 0.10 to 0.12 mm at 40 cm for an individual with 20/20 Snellen acuity [ 11 ]. A variation of 5% of volume in a 7 mm aneurysm equals to an overall change in diameter of 0.11 mm which would most probably go unnoticed for a surgeon focused on another task than actually trying to assess aneurysm wall motion. Thirdly, during anesthesia, arterial pressure and pulse pressure are usually kept lower than normal. In a recent report, systolic blood pressure decreased by an average of 39 mmHg between the baseline and the lowest point during aneurysm surgery whereas the diastolic pressure was only decreased by 27 mmHg [ 12 ] meaning that the pulse pressure also decreased during surgery. As was previously published, pulse pressure was the main determinant for aneurysm pulsation in an in-vitro setting [ 13 ]. Tube curve radius did not impact aneurysm pulsation: in our setting there was no correlation between curve radius and volume pulsation. We however had to exclude the aneurysm with the lowest curve radius due to manufacturing issues. These models were made by hand and the manufacturer indeed mentions that the wall thickness may vary up to twice the nominal thickness. Results with the 10 mm curve radius model showed a completely different behavior than the other three but further investigation – measuring the change in volume in non-pulsatile flow with increasing mean pressures – indeed revealed that the volume changes in the 10 mm model were only approximately half of the volume changes of the other models, meaning a much lower compliance of the wall. Attempting to correct for this seemed at too great of a risk to introduce bias in our results. CFD was performed on the four models revealing variation in the simulated intra-aneurysmal flow, verifying that the geometry of our models indeed had an impact on aneurysm hemodynamics. Inflow jet velocity at the distal wall increased with curvature which is in agreement with published studies. Several studies showed that, in curved vessels, high velocity, wall shear stress and wall shear rate is seen at the distal wall of aneurysms and that such morphology was associated with aneurysm rupture [ 9 , 14 ]. The effect of mechanical stress on vessel wall remodeling [ 15 ] is therefore a more probable cause of eventual rupture than a localized increase pressure leading to abnormal wall motion and subsequent rupture. This study has limitations: 1) the in vitro design cannot fully grasp the complexity of the living, however this study would not be feasible in human subject; 2) silicon properties are somewhat different from vessel walls but it is widely recognized as a good approximation and used in many simulation test benches; 3) manufacturing problems forced us to exclude one of the models from the second experiment but it seemed less likely to introduce bias than the alternative which was trying to correct for the difference in wall thickness. In conclusion, this study shows that in a simplified in vitro setting: 1) an increase in external – “intracranial” – pressure leads to a decrease in pulsation amplitude and vice versa although the variation is marginal in the normal range of arterial pulse pressure and intracranial pressure; 2) the parent vessel curvature is not correlated with pulsation amplitude although additional study would be needed to confirm this second result. Declarations Author Contribution A.V., K.Z.B. and K.C. designed the study.A.V., K.C. and R.T. conducted the "pressure" experiments.A.V., K.C. and S.H. conducted the "curvature" experiments.A.V., K.C., R.T. and K.Z.B. analyzed the results of the "pressure" experiments.A.V., K.C., S.H. and K.Z.B. analyzed the results of the "curvature" experiments.A.V. wrote the main manuscript text.A.V. and K.C. prepared tables and figures. All authors reviewed the manuscript. Data Availability All data is based on CT-scanners acquisitions that cannot readily be made accessible online (close to 1 million high resolution images with long file names that are often not supported by various program). We have provided as supplementary data the first raw analysis of aneurysm volume and surface area for each timsestep of each experiment. If requested the CT images could be stored on a hard drive and physically shipped. References Meyer, F. B., Huston, J. & Riederer, S. S. Pulsatile increases in aneurysm size determined by cine phase-contrast MR angiography. J. Neurosurg. 78 , 879–883 (1993). Kato, Y. et al. Prediction of impending rupture in aneurysms using 4D-CTA: histopathological verification of a real-time minimally invasive tool in unruptured aneurysms. Minim. Invasive Neurosurg. MIN 47 , 131–135 (2004). Ishida, F., Ogawa, H., Simizu, T., Kojima, T. & Taki, W. Visualizing the dynamics of cerebral aneurysms with four-dimensional computed tomographic angiography. Neurosurgery 57 , 460–471; discussion 460-471 (2005). Oubel, E. et al. Wall motion estimation in intracranial aneurysms. Physiol. Meas. 31 , 1119–1135 (2010). Vanrossomme, A. E., Eker, O. F., Thiran, J.-P., Courbebaisse, G. P. & Zouaoui Boudjeltia, K. Intracranial Aneurysms: Wall Motion Analysis for Prediction of Rupture. AJNR Am. J. Neuroradiol. 36 , 1796–1802 (2015). Wardlaw, J. M., Cannon, J., Statham, P. F. & Price, R. Does the size of intracranial aneurysms change with intracranial pressure? Observations based on color ‘power’ transcranial Doppler ultrasound. J. Neurosurg. 88 , 846–850 (1998). Hassan, T. et al. A proposed parent vessel geometry-based categorization of saccular intracranial aneurysms: computational flow dynamics analysis of the risk factors for lesion rupture. J. Neurosurg. 103 , 662–680 (2005). Lauric, A., Hippelheuser, J., Safain, M. G. & Malek, A. M. Curvature effect on hemodynamic conditions at the inner bend of the carotid siphon and its relation to aneurysm formation. J. Biomech. 47 , 3018–3027 (2014). Hoi, Y. et al. Effects of arterial geometry on aneurysm growth: three-dimensional computational fluid dynamics study. J. Neurosurg. 101 , 676–681 (2004). Futami, K. et al. Parent artery curvature influences inflow zone location of unruptured sidewall internal carotid artery aneurysms. AJNR Am. J. Neuroradiol. 36 , 342–348 (2015). Yanoff, M. & Duker, J. S. in Ophtalmology 3rd Edition , p. 54 (Elsevier, St. Louis, MO, 2008). Thongrong, C., Kasemsiri, P., Duangthongphon, P. & Kitkhuandee, A. Appropriate Blood Pressure in Cerebral Aneurysm Clipping for Prevention of Delayed Ischemic Neurologic Deficits. Anesthesiol. Res. Pract. 2020 , 6539456 (2020). Vanrossomme, A. E., Chodzyński, K. J., Eker, O. F. & Boudjeltia, K. Z. Development of experimental ground truth and quantification of intracranial aneurysm pulsation in a patient. Sci. Rep. 11 , 9441 (2021). Meng, H., Wang, Z., Kim, M., Ecker, R. D. & Hopkins, L. N. Saccular aneurysms on straight and curved vessels are subject to different hemodynamics: implications of intravascular stenting. AJNR Am. J. Neuroradiol. 27 , 1861–1865 (2006). Katoh, K. Effects of Mechanical Stress on Endothelial Cells In Situ and In Vitro. Int. J. Mol. Sci. 24 , 16518 (2023). Additional Declarations No competing interests reported. Supplementary Files CTResultPextExp1.xlsx CTResultPextExp2.xlsx CTResultPextExp3.xlsx CTResultCurvExp1.xlsx CTResultCurvExp2.xlsx CTResultCurvExp3.xlsx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8211535","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":594042792,"identity":"24a8dc5e-de12-44ef-a5bd-71ec5f11796f","order_by":0,"name":"Axel E. 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A: reservoir ; B: centrifugal pump ; C: anti-reflow valve ; D : piston pump ; E : aneurysm model ; G: flow meter ; H: scanner gantry (half).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/eeb0846e01c05b65acc58f42.png"},{"id":103503863,"identity":"e8a60922-0577-4a4c-ada7-665fe8dd7165","added_by":"auto","created_at":"2026-02-26 13:03:40","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":182699,"visible":true,"origin":"","legend":"\u003cp\u003eCharacteristics of aneurysm phantoms as ordered. A: straight ; B: 20 mm radius of curvature ; C: 10 mm radius of curvature ; D: 30 mm radius of curvature.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/300a407d1d45bb1f09d39ea2.png"},{"id":103503849,"identity":"dfbe3371-8d95-4d86-9dac-08bf8a2a6774","added_by":"auto","created_at":"2026-02-26 13:03:21","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":38354,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eAverage pulsation amplitude as a function of external pressure at different pulse pressure, with regression lines and correlation coefficients. Whiskers represent standard deviation.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ePP: pulse pressure; APA: average pulsation amplitude ; EP : external pressure\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/1fadad3827603d5efab01982.png"},{"id":103062715,"identity":"32fdfd45-228d-4f93-a276-279166118a19","added_by":"auto","created_at":"2026-02-20 10:30:16","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":21229,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eFigure 5. Average aneurysm volume as a function of external pressure (average of the three repetitions) with regression line and correlation coefficient. Whiskers represent standard deviation.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAAV: average aneurysm volume; EP: external pressure\u003c/em\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/0a3b6b48a32f45cd7bf6e78c.png"},{"id":103062717,"identity":"adb90975-3417-4fa8-89a4-068208829d80","added_by":"auto","created_at":"2026-02-20 10:30:16","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":51744,"visible":true,"origin":"","legend":"\u003cp\u003eFigure 6. Relative volume change of the model as a function of the average pressure inside the system (over atmospheric pressure) in the absence of pulsation. x mm-RC model : aneurysm model with a radius of curvature of x mm.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/5e4c3286feb5d8e9d219cf03.png"},{"id":103504601,"identity":"90039c10-824d-44ce-be43-f2a8d358f265","added_by":"auto","created_at":"2026-02-26 13:20:42","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":422521,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eFigure 7. Intra-aneurysmal velocity and pressure maps according to computational fluid dynamics analysis. A. Straight model. B, C \u0026amp; D : models with a radius of curvature of 30 mm (B), 20 mm (C) and 10 mm (D).\u003c/em\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/d4430d6a2f068e42b470bb09.png"},{"id":106865291,"identity":"4ad1e4da-145b-4cec-897f-5f14e3a544de","added_by":"auto","created_at":"2026-04-14 08:58:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1949749,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/63a6b098-622f-4001-9af2-74725343c16a.pdf"},{"id":103504425,"identity":"868d67d8-00a8-4a5c-bf7d-70401955d483","added_by":"auto","created_at":"2026-02-26 13:19:50","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":250245,"visible":true,"origin":"","legend":"","description":"","filename":"CTResultPextExp1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/562601beb51b12c012d304bb.xlsx"},{"id":103062721,"identity":"14278e72-308a-4063-bf8e-0be02afe3e9b","added_by":"auto","created_at":"2026-02-20 10:30:16","extension":"xlsx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":124925,"visible":true,"origin":"","legend":"","description":"","filename":"CTResultPextExp2.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/c30f2860246ba9454f995992.xlsx"},{"id":103062718,"identity":"2fd8a91b-32a0-4080-838d-e18daa8cac47","added_by":"auto","created_at":"2026-02-20 10:30:16","extension":"xlsx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":125043,"visible":true,"origin":"","legend":"","description":"","filename":"CTResultPextExp3.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/0f19f0fe380e7fae4a279129.xlsx"},{"id":103062719,"identity":"e1444314-e2d5-498a-b140-e53d7ee4d444","added_by":"auto","created_at":"2026-02-20 10:30:16","extension":"xlsx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":104996,"visible":true,"origin":"","legend":"","description":"","filename":"CTResultCurvExp1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/be3bb1a8d36ba297297a7044.xlsx"},{"id":103062720,"identity":"bbbd0d3e-e151-4eb5-9329-8eaf6b3ff83e","added_by":"auto","created_at":"2026-02-20 10:30:16","extension":"xlsx","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":103329,"visible":true,"origin":"","legend":"","description":"","filename":"CTResultCurvExp2.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/cb9f4df535c004a5d6445a4e.xlsx"},{"id":103062723,"identity":"bfaf9242-1264-4c3a-946f-e9b3ae7d4e3b","added_by":"auto","created_at":"2026-02-20 10:30:16","extension":"xlsx","order_by":6,"title":"","display":"","copyAsset":false,"role":"supplement","size":104989,"visible":true,"origin":"","legend":"","description":"","filename":"CTResultCurvExp3.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8211535/v1/a68d36d156313ff442b3d690.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Intracranial aneurysms: in vitro study of “intracranial” pressure and parent vessel curvature as potential modifiers of aneurysm pulsation amplitude","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIntracranial aneurysm pulsation \u0026ndash; or wall motion \u0026ndash; has been proposed as a potential criterion to identify aneurysms that are more likely to rupture, and to rupture sooner [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Although several imaging techniques have been used to detect and quantify aneurysm pulsation [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], factors that might affect aneurysm pulsation and its measurement have not been identified. Wardlaw et al hypothesized that intracranial pressure could modulate the amplitude of pulsation by increasing or decreasing tensile forces in the aneurysm wall. According to these authors, an decrease in intracranial pressure leads to an increase in aneurysm volume. The increase in volume increases the tensile forces in the wall which could reduce wall motion. This could explain why neurosurgeons usually do not detect aneurysm pulsation during surgery [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. This hypothesis however was not properly tested.\u003c/p\u003e \u003cp\u003eSimilarly, parent vessel curvature is known to modify the intra-aneurysmal fluid dynamics as studied both by computational fluid dynamics and 4D-flow magnetic resonance imaging [\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. However, the impact of this parameter on aneurysm pulsation is not clear and has not, to our knowledge, been formally tested.\u003c/p\u003e \u003cp\u003eTherefore, the aim of our study has been to test in an in vitro setting whether external \u0026ndash; \u0026ldquo;intracranial\u0026rdquo; \u0026ndash; pressure or parent vessel curvature had a detectable impact on the aneurysm pulsation, and how it impacted it.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003eAcquisitions were made out on a 64 detector-rows CT scanner (Somatom Definition AS, Siemens Healthineers, Erlanger, Germany) equipped with a z-flying focal spot X-ray tube (Straton, Siemens). All acquisitions were done with a stationary table using the following parameters: peak kilovoltage\u0026thinsp;=\u0026thinsp;120 kVp; time-current product\u0026thinsp;=\u0026thinsp;190 mAs; acquisition scan time\u0026thinsp;=\u0026thinsp;5 s; tube rotation time\u0026thinsp;=\u0026thinsp;0.3 s. Each acquisition was reconstructed as a series of volumes each containing 64 slices with a nominal thickness of 0,6 mm with a time interval of 50 ms between each successive volume. This resulted in 94 volumes per acquisition.\u003c/p\u003e \u003cp\u003eBoth parts of this study were carried out using a test bench that could apply reproducible pulsatile flow to silicon aneurysm phantoms (European patent reference EP2779144\u0026mdash;Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe circuit was filled with a glycerine and water solution, the viscosity of which was similar to the average human blood viscosity (3.45 x 10\u0026thinsp;\u0026minus;\u0026thinsp;3 Pa.s at 20\u0026deg;C). Iopromide 370 mgI/ml (Ultravist, Bayer HealthCare, Leverkusen, Germany) was then added to the aforementioned solution at a ratio of 1:4 in order to achieve sufficient opacification. The centrifugal pump was adjusted to generate a mean flow of 180 ml/min. Piston pump frequency was set at 1.5 Hz and pulse pressure was gradually increased as detailed below. The mean pressure in the circuit was maintained at 90 mmHg using valves.\u003c/p\u003e \u003cp\u003ePulsation was defined as the difference between the highest and lowest volume of each pulse cycle. Average volume pulsation and standard deviations were calculated for each experiment.\u003c/p\u003e \u003cp\u003eAll pressure values are to be understood as taking atmospheric pressure as reference (0 mmHg).\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePart 1 \u0026ndash; Intracranial pressure and pulsation\u003c/h2\u003e \u003cp\u003eTo mimic intracranial pressure, a spherical silicon aneurysm phantom on a straight silicon tube connected to the test bench described above was put inside a sealed pressure chamber. This chamber consisted of a poly(methyl methacrylate) box equipped with a manometric valve. Pressure inside that box \u0026ndash; later referred to as \u0026ldquo;external pressure\u0026rdquo; \u0026ndash; was set at 0 mmHg, 12.5 mmHg, 25 mmHg, 50 mmHg, and 70 mmHg.\u003c/p\u003e \u003cp\u003eFor each value of external pressure, piston pump voltage was set at 0 V, 1 V, 1.5 V, 2 V, and 2.5 V for the first two repetition of the experiment, generating pulse pressures of approximately 0 mmHg, 70 mmHg, 115 mmHg, 190 mmHg and 270 mmHg respectively. The pulse pressures were measured during the experiment and recorded.\u003c/p\u003e \u003cp\u003e4D-CTA acquisitions were made for each combination of external pressure and pulse pressure.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePart 2 – Parent vessel curvature and pulsation\u003c/h3\u003e\n\u003cp\u003eFour different models of silicon aneurysm (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) were custom made by Elastrat (Geneva, Switzerland). The radius of curvature (RC) of the silicon tube at the aneurysm neck was 10 mm, 20 mm and 30 mm in the first three models. The last one was straight.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe tubes were stabilized using 3D printed guides, to ensure there would be no variation of curvature during the acquisitions or between the repetitions.\u003c/p\u003e \u003cp\u003eFor each value of external pressure, piston pump voltage was set at 0 V, 1 V, 1.5 V, 2 V, and 2.5 V generating pulse pressures of approximately 0 mmHg, 70 mmHg, 115 mmHg, 190 mmHg and 270 mmHg respectively. The pulse pressures were measured during the experiment and recorded.\u003c/p\u003e \u003cp\u003e4D-CTA acquisitions were made for each combination of curvature \u0026ndash; defined as 1/RC \u0026ndash; and pulse pressure. The whole set of experiments was repeated 3 times to ensure that the findings were reproducible.\u003c/p\u003e \u003cp\u003eIn addition to this, computational fluid dynamics was used to determine velocity magnitude maps inside the aneurysm models.\u003c/p\u003e\n\u003ch3\u003eImage post-processing and analysis\u003c/h3\u003e\n\u003cp\u003ePulsation analysis was performed using a semi-automated method that was developed in the lab, using MATLAB 2015b software (MathWorks, Natcick, MA) with additional toolboxes (Parallel Computing Toolbox 6.7 and Image Processing Toolbox 9.3). DICOM imaged were organized as a three-dimensional matrix where X and Y units were the pixel size and Z unit was the slice thickness. \u0026ldquo;Imwarp\u0026rdquo; MATLAB function was used to perform a linear interpolation to obtain isotropic voxels with a nominal size equal to that of the original X-Y pixels. The grey scale matrix was converted to a black-and-white matrix using a Hounsfield Unit threshold that was defined visually for each acquisition by a radiologist with more than 10 years of expertise in cardiovascular imaging, in order to best fit the aneurysm. All voxels with an attenuation value that was higher than the defined threshold were given a value of 1, those lower than the threshold a value of 0. Masks were then applied to the resulting 3D matrix to remove the tube and extract only the aneurysm. The first mask was applied to extract a smaller region of interest containing the aneurysm to remove any potential close object and to reduce calculation time, using \u0026ldquo;imcrop\u0026rdquo; MATLAB function. The second mask was an XY elliptic mask applied manually on the tube on one image using \u0026ldquo;imellipse\u0026rdquo; MATLAB function, to remove the tube and the contrast medium within it. As the tubes were not all straight, the position of this mask was corrected automatically using an algorithm that followed the center of the tube on each 2D image. The resulting matrix contained only voxels from the aneurysm with a value of 1, all the other voxels being replaced by 0.\u003c/p\u003e \u003cp\u003eTo calculate the volume of the aneurysm sac, the following equation was used:\u003c/p\u003e \u003cp\u003eVolume (mm\u0026sup3;)\u0026thinsp;=\u0026thinsp;N\u003csub\u003eV1\u003c/sub\u003e x X\u003csub\u003eV\u003c/sub\u003e x Y\u003csub\u003eV\u003c/sub\u003e x Z\u003csub\u003eV\u003c/sub\u003e with\u003c/p\u003e \u003cp\u003eN\u003csub\u003eV1\u003c/sub\u003e = the total number of voxels with a value of 1\u003c/p\u003e \u003cp\u003eX\u003csub\u003eV\u003c/sub\u003e, Y\u003csub\u003eV\u003c/sub\u003e and Z\u003csub\u003eV\u003c/sub\u003e = the size of each voxel in the X, Y and Z directions respectively\u003c/p\u003e \u003cp\u003ePulsation amplitude was calculated as follows:\u003c/p\u003e \u003cp\u003eAVP (%)\u0026thinsp;=\u0026thinsp;100 x (AV\u003csub\u003emax\u003c/sub\u003e \u0026ndash; AV\u003csub\u003emin\u003c/sub\u003e) / AV\u003csub\u003emean\u003c/sub\u003e with\u003c/p\u003e \u003cp\u003eAVP\u0026thinsp;=\u0026thinsp;aneurysm volume pulsation or pulsation amplitude\u003c/p\u003e \u003cp\u003eAV\u003csub\u003emax\u003c/sub\u003e, AV\u003csub\u003emin\u003c/sub\u003e and AV\u003csub\u003emean\u003c/sub\u003e = maximum, minimum and mean aneurysm volume\u003c/p\u003e \u003cp\u003eThis whole process was repeated for each time step.\u003c/p\u003e\n\u003ch3\u003eStatistics\u003c/h3\u003e\n\u003cp\u003eSigmaplot12 software was used. Comparisons were done using One-Way ANOVA. Normality was calculated by using the Shapiro-Wilk's test. A probability level of p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered as statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003ePart 1 \u0026ndash; Intracranial pressure and pulsation\u003c/h2\u003e \u003cp\u003eThe relation between pulsation and external pressure was linear in the range that was tested. The average volume amplitude of all three repetition with standard deviations are summarized in Table\u003c/p\u003e \u003cp\u003e1.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEP (mmHg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePP\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (mmHg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAAV\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (mm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAPA\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (mm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0\u0026thinsp;\u0026plusmn;\u0026thinsp;0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e532\u0026thinsp;\u0026plusmn;\u0026thinsp;11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e0.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0\u0026thinsp;\u0026plusmn;\u0026thinsp;0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e537\u0026thinsp;\u0026plusmn;\u0026thinsp;20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e0.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0\u0026thinsp;\u0026plusmn;\u0026thinsp;0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e541\u0026thinsp;\u0026plusmn;\u0026thinsp;20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e0.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0\u0026thinsp;\u0026plusmn;\u0026thinsp;0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e530\u0026thinsp;\u0026plusmn;\u0026thinsp;15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e0.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0\u0026thinsp;\u0026plusmn;\u0026thinsp;0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e518\u0026thinsp;\u0026plusmn;\u0026thinsp;11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e0.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e69.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e536\u0026thinsp;\u0026plusmn;\u0026thinsp;7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e8.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.95\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e69.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e525\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e8.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.80\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e69.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e535\u0026thinsp;\u0026plusmn;\u0026thinsp;21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e7.80\u0026thinsp;\u0026plusmn;\u0026thinsp;1.27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e69.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e528\u0026thinsp;\u0026plusmn;\u0026thinsp;24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e7.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.91\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e69.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e523\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e6.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e112.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e536\u0026thinsp;\u0026plusmn;\u0026thinsp;6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e14.03\u0026thinsp;\u0026plusmn;\u0026thinsp;2.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e112.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e532\u0026thinsp;\u0026plusmn;\u0026thinsp;9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e13.22\u0026thinsp;\u0026plusmn;\u0026thinsp;2.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e112.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e530\u0026thinsp;\u0026plusmn;\u0026thinsp;12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e12.97\u0026thinsp;\u0026plusmn;\u0026thinsp;2.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e112.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e528\u0026thinsp;\u0026plusmn;\u0026thinsp;13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e12.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e112.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e522\u0026thinsp;\u0026plusmn;\u0026thinsp;10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e12.04\u0026thinsp;\u0026plusmn;\u0026thinsp;2.39\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e186.6\u0026thinsp;\u0026plusmn;\u0026thinsp;8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e537\u0026thinsp;\u0026plusmn;\u0026thinsp;16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e22.70\u0026thinsp;\u0026plusmn;\u0026thinsp;3.68\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e186.6\u0026thinsp;\u0026plusmn;\u0026thinsp;8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e542\u0026thinsp;\u0026plusmn;\u0026thinsp;20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e22.73\u0026thinsp;\u0026plusmn;\u0026thinsp;4.27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e186.6\u0026thinsp;\u0026plusmn;\u0026thinsp;8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e533\u0026thinsp;\u0026plusmn;\u0026thinsp;13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e21.79\u0026thinsp;\u0026plusmn;\u0026thinsp;2.68\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e186.6\u0026thinsp;\u0026plusmn;\u0026thinsp;8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e531\u0026thinsp;\u0026plusmn;\u0026thinsp;12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e21.15\u0026thinsp;\u0026plusmn;\u0026thinsp;3.29\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e186.6\u0026thinsp;\u0026plusmn;\u0026thinsp;8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e257\u0026thinsp;\u0026plusmn;\u0026thinsp;13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e20.41\u0026thinsp;\u0026plusmn;\u0026thinsp;2.99\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e267.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e540\u0026thinsp;\u0026plusmn;\u0026thinsp;13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e35.41\u0026thinsp;\u0026plusmn;\u0026thinsp;4.13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e267.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e530\u0026thinsp;\u0026plusmn;\u0026thinsp;13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e33.88\u0026thinsp;\u0026plusmn;\u0026thinsp;2.77\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e267.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e535\u0026thinsp;\u0026plusmn;\u0026thinsp;11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e32.02\u0026thinsp;\u0026plusmn;\u0026thinsp;5.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e267.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e532\u0026thinsp;\u0026plusmn;\u0026thinsp;13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e31.17\u0026thinsp;\u0026plusmn;\u0026thinsp;4.93\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e267.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e531\u0026thinsp;\u0026plusmn;\u0026thinsp;14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e30.06\u0026thinsp;\u0026plusmn;\u0026thinsp;5.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eEP\u0026nbsp;: external pressure\u0026nbsp;; PP\u0026nbsp;: pulse pressure\u0026nbsp;; SD\u0026nbsp;: standard deviation\u0026nbsp;; AAV\u0026nbsp;: average aneurysm volume\u0026nbsp;; APA\u0026nbsp;: average pulsation amplitude.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eResults show that for each non-null value of pulse pressure, pulsation decreased with increasing external pressure (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePP: pulse pressure; APA: average pulsation amplitude ; EP : external pressure\u003c/h3\u003e\n\u003cp\u003eAdditionally the average volume of the aneurysm decreased by 2 to 3% between 0 and 70 mmHg of external pressure (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eAAV: average aneurysm volume; EP: external pressure\u003c/h3\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003ePart 2 \u0026ndash; Parent vessel curvature and pulsation\u003c/h2\u003e \u003cp\u003eResults of the three repetitions are summarized in Table\u0026nbsp;2.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e \u003ccolgroup cols=\"15\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"12\" nameend=\"c13\" namest=\"c2\"\u003e \u003cp\u003eRelative pulsation amplitude (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c15\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePP (mmHg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eStr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eR10\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e \u003cp\u003eR20\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c13\" namest=\"c11\"\u003e \u003cp\u003eR30\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c14\"\u003e \u003cp\u003eStr vs R10 vs R20 vs R30\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c15\"\u003e \u003cp\u003eStr vs R20 vs R30\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eR1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eR2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eR3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eR1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eR2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eR3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eR1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eR2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eR3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eR1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003eR2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003eR3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c14\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c15\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e0\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e0.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e70\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e3.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e3.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e3.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e3.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e\u003cb\u003e0.01\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e0.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e115\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e4.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e6.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e6.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e5.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e5.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e0.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e190\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e8.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e7.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e9.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e10.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e8.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e8.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e0.48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e270\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e10.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e12.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e10.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e12.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e14.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e11.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e12.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e0.70\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"15\" nameend=\"c15\" namest=\"c1\"\u003e \u003cp\u003eStr : straight model ; R10, R20, R30 : models with a 10 mm, 20 mm or 30 radius of curvature respectively ; PP : pulse pressure.\u003c/p\u003e \u003cp\u003eComparisons were done using One-Way ANOVA. A probability level of p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered as statistically significant.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTaking all models into consideration, there was no significant different between pulsation amplitudes except at 70 mmHg. However, further investigation showed that the silicon of the 10 mm-RC aneurysm was thicker and less compliant than the other three : the models volume was quantify for different values of internal pressure, in the absence of pulsation, and the relative variation compared to 0 mmHg interior pressure (over atmospheric pressure) was calculated for each model (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eNormalizing the compliance of each model to the smallest one (10mm-RC), normalized deformation coefficient were quantified as follows: 1 for the 10 mm-RC model; 2.01 for the 20mm-RC model ; 2.23 for the 30mm-RC model and 1.81 for the straight model. As the compliance of the 10 mm-RC model was approximately half of the compliance of the other models, it was decided to exclude 10 mm-RC model as it induced a significant bias.\u003c/p\u003e \u003cp\u003eExcluding the data from the 10 mm-RC model, there was no significant difference between pulsation amplitudes of straight, 20 mm-RC and 30 mm-RC aneurysm models.\u003c/p\u003e \u003cp\u003eComputational fluid dynamic analysis however shows different velocity and pressure maps with an increase in inflow jet velocity and a slight increase in intra-aneurysmal pressure with increasing curvature (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur results show that 1) contrary to what had been hypothesized before, in an in vitro setting, an increase in external pressure reduces the amplitude of pulsation of the aneurysm model, although the total volume of the aneurysm decreases; 2) tube curve radius does not seem to impact pulsation amplitude.\u003c/p\u003e \u003cp\u003eIn our simplified in vitro setting, an increase in external pressure led to a decrease in total aneurysm volume but that was not accompanied by an increase in pulsation amplitude as had been hypothesized by Wardlaw [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. An increase in external pressure actually reduced wall motion. If wall tensile forces are obviously a crucial determinant of pulsation amplitude, the importance of its variation was probably overestimated. Tensile forces are proportional to \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\sqrt{r}\\)\u003c/span\u003e\u003c/span\u003e. As we mentioned above, the variation in aneurysm volume between 0 and 70 mmHg of external pressure was only 2 to 3%. The resulting variation in tensile forces would therefore be negligible compared to the effect of external pressure opposing the outward expansion of the aneurysm, which is proportional to the external pressure.\u003c/p\u003e \u003cp\u003eWhat could therefore explain the absence of visible pulsation during surgery? Our hypothesis is a combination of three factors. Firstly, even though a decrease in external pressure was associated with an increase in pulsation amplitude, the effect was very small for the normal range of arterial pulse pressure \u0026ndash; 30 to 60 mmHg \u0026ndash; and intracranial pressure \u0026ndash; 0 to 15 mmHg if we consider open neurosurgery within the range. Secondly, the human eye is not very effective at detecting motions of very small amplitude. The usually admitted angular resolution of the human eye is approximately 1 arcminute which translate to 0.10 to 0.12 mm at 40 cm for an individual with 20/20 Snellen acuity [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. A variation of 5% of volume in a 7 mm aneurysm equals to an overall change in diameter of 0.11 mm which would most probably go unnoticed for a surgeon focused on another task than actually trying to assess aneurysm wall motion. Thirdly, during anesthesia, arterial pressure and pulse pressure are usually kept lower than normal. In a recent report, systolic blood pressure decreased by an average of 39 mmHg between the baseline and the lowest point during aneurysm surgery whereas the diastolic pressure was only decreased by 27 mmHg [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] meaning that the pulse pressure also decreased during surgery. As was previously published, pulse pressure was the main determinant for aneurysm pulsation in an in-vitro setting [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTube curve radius did not impact aneurysm pulsation: in our setting there was no correlation between curve radius and volume pulsation. We however had to exclude the aneurysm with the lowest curve radius due to manufacturing issues. These models were made by hand and the manufacturer indeed mentions that the wall thickness may vary up to twice the nominal thickness. Results with the 10 mm curve radius model showed a completely different behavior than the other three but further investigation \u0026ndash; measuring the change in volume in non-pulsatile flow with increasing mean pressures \u0026ndash; indeed revealed that the volume changes in the 10 mm model were only approximately half of the volume changes of the other models, meaning a much lower compliance of the wall. Attempting to correct for this seemed at too great of a risk to introduce bias in our results.\u003c/p\u003e \u003cp\u003eCFD was performed on the four models revealing variation in the simulated intra-aneurysmal flow, verifying that the geometry of our models indeed had an impact on aneurysm hemodynamics. Inflow jet velocity at the distal wall increased with curvature which is in agreement with published studies. Several studies showed that, in curved vessels, high velocity, wall shear stress and wall shear rate is seen at the distal wall of aneurysms and that such morphology was associated with aneurysm rupture [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The effect of mechanical stress on vessel wall remodeling [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] is therefore a more probable cause of eventual rupture than a localized increase pressure leading to abnormal wall motion and subsequent rupture.\u003c/p\u003e \u003cp\u003eThis study has limitations: 1) the \u003cem\u003ein vitro\u003c/em\u003e design cannot fully grasp the complexity of the living, however this study would not be feasible in human subject; 2) silicon properties are somewhat different from vessel walls but it is widely recognized as a good approximation and used in many simulation test benches; 3) manufacturing problems forced us to exclude one of the models from the second experiment but it seemed less likely to introduce bias than the alternative which was trying to correct for the difference in wall thickness.\u003c/p\u003e \u003cp\u003eIn conclusion, this study shows that in a simplified in vitro setting: 1) an increase in external \u0026ndash; \u0026ldquo;intracranial\u0026rdquo; \u0026ndash; pressure leads to a decrease in pulsation amplitude and vice versa although the variation is marginal in the normal range of arterial pulse pressure and intracranial pressure; 2) the parent vessel curvature is not correlated with pulsation amplitude although additional study would be needed to confirm this second result.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eA.V., K.Z.B. and K.C. designed the study.A.V., K.C. and R.T. conducted the \"pressure\" experiments.A.V., K.C. and S.H. conducted the \"curvature\" experiments.A.V., K.C., R.T. and K.Z.B. analyzed the results of the \"pressure\" experiments.A.V., K.C., S.H. and K.Z.B. analyzed the results of the \"curvature\" experiments.A.V. wrote the main manuscript text.A.V. and K.C. prepared tables and figures. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data is based on CT-scanners acquisitions that cannot readily be made accessible online (close to 1 million high resolution images with long file names that are often not supported by various program). We have provided as supplementary data the first raw analysis of aneurysm volume and surface area for each timsestep of each experiment. If requested the CT images could be stored on a hard drive and physically shipped.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eMeyer, F. B., Huston, J. \u0026amp; Riederer, S. S. Pulsatile increases in aneurysm size determined by cine phase-contrast MR angiography. \u003cem\u003eJ. Neurosurg.\u003c/em\u003e \u003cstrong\u003e78\u003c/strong\u003e, 879\u0026ndash;883 (1993).\u003c/li\u003e\n \u003cli\u003eKato, Y. \u003cem\u003eet al.\u003c/em\u003e Prediction of impending rupture in aneurysms using 4D-CTA: histopathological verification of a real-time minimally invasive tool in unruptured aneurysms. \u003cem\u003eMinim. Invasive Neurosurg. MIN\u003c/em\u003e \u003cstrong\u003e47\u003c/strong\u003e, 131\u0026ndash;135 (2004).\u003c/li\u003e\n \u003cli\u003eIshida, F., Ogawa, H., Simizu, T., Kojima, T. \u0026amp; Taki, W. Visualizing the dynamics of cerebral aneurysms with four-dimensional computed tomographic angiography. \u003cem\u003eNeurosurgery\u003c/em\u003e \u003cstrong\u003e57\u003c/strong\u003e, 460\u0026ndash;471; discussion 460-471 (2005).\u003c/li\u003e\n \u003cli\u003eOubel, E. \u003cem\u003eet al.\u003c/em\u003e Wall motion estimation in intracranial aneurysms. \u003cem\u003ePhysiol. Meas.\u003c/em\u003e \u003cstrong\u003e31\u003c/strong\u003e, 1119\u0026ndash;1135 (2010).\u003c/li\u003e\n \u003cli\u003eVanrossomme, A. E., Eker, O. F., Thiran, J.-P., Courbebaisse, G. P. \u0026amp; Zouaoui Boudjeltia, K. Intracranial Aneurysms: Wall Motion Analysis for Prediction of Rupture. \u003cem\u003eAJNR Am. J. Neuroradiol.\u003c/em\u003e \u003cstrong\u003e36\u003c/strong\u003e, 1796\u0026ndash;1802 (2015).\u003c/li\u003e\n \u003cli\u003eWardlaw, J. M., Cannon, J., Statham, P. F. \u0026amp; Price, R. Does the size of intracranial aneurysms change with intracranial pressure? Observations based on color \u0026lsquo;power\u0026rsquo; transcranial Doppler ultrasound. \u003cem\u003eJ. Neurosurg.\u003c/em\u003e \u003cstrong\u003e88\u003c/strong\u003e, 846\u0026ndash;850 (1998).\u003c/li\u003e\n \u003cli\u003eHassan, T. \u003cem\u003eet al.\u003c/em\u003e A proposed parent vessel geometry-based categorization of saccular intracranial aneurysms: computational flow dynamics analysis of the risk factors for lesion rupture. \u003cem\u003eJ. Neurosurg.\u003c/em\u003e \u003cstrong\u003e103\u003c/strong\u003e, 662\u0026ndash;680 (2005).\u003c/li\u003e\n \u003cli\u003eLauric, A., Hippelheuser, J., Safain, M. G. \u0026amp; Malek, A. M. Curvature effect on hemodynamic conditions at the inner bend of the carotid siphon and its relation to aneurysm formation. \u003cem\u003eJ. Biomech.\u003c/em\u003e \u003cstrong\u003e47\u003c/strong\u003e, 3018\u0026ndash;3027 (2014).\u003c/li\u003e\n \u003cli\u003eHoi, Y. \u003cem\u003eet al.\u003c/em\u003e Effects of arterial geometry on aneurysm growth: three-dimensional computational fluid dynamics study. \u003cem\u003eJ. Neurosurg.\u003c/em\u003e \u003cstrong\u003e101\u003c/strong\u003e, 676\u0026ndash;681 (2004).\u003c/li\u003e\n \u003cli\u003eFutami, K. \u003cem\u003eet al.\u003c/em\u003e Parent artery curvature influences inflow zone location of unruptured sidewall internal carotid artery aneurysms. \u003cem\u003eAJNR Am. J. Neuroradiol.\u003c/em\u003e \u003cstrong\u003e36\u003c/strong\u003e, 342\u0026ndash;348 (2015).\u003c/li\u003e\n \u003cli\u003eYanoff, M. \u0026amp; Duker, J. S. in \u003cem\u003eOphtalmology 3rd Edition\u003c/em\u003e, p. 54 (Elsevier, St. Louis, MO, 2008).\u003c/li\u003e\n \u003cli\u003eThongrong, C., Kasemsiri, P., Duangthongphon, P. \u0026amp; Kitkhuandee, A. Appropriate Blood Pressure in Cerebral Aneurysm Clipping for Prevention of Delayed Ischemic Neurologic Deficits. \u003cem\u003eAnesthesiol. Res. Pract.\u003c/em\u003e \u003cstrong\u003e2020\u003c/strong\u003e, 6539456 (2020).\u003c/li\u003e\n \u003cli\u003eVanrossomme, A. E., Chodzyński, K. J., Eker, O. F. \u0026amp; Boudjeltia, K. Z. Development of experimental ground truth and quantification of intracranial aneurysm pulsation in a patient. \u003cem\u003eSci. Rep.\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, 9441 (2021).\u003c/li\u003e\n \u003cli\u003eMeng, H., Wang, Z., Kim, M., Ecker, R. D. \u0026amp; Hopkins, L. N. Saccular aneurysms on straight and curved vessels are subject to different hemodynamics: implications of intravascular stenting. \u003cem\u003eAJNR Am. J. Neuroradiol.\u003c/em\u003e \u003cstrong\u003e27\u003c/strong\u003e, 1861\u0026ndash;1865 (2006).\u003c/li\u003e\n \u003cli\u003eKatoh, K. Effects of Mechanical Stress on Endothelial Cells In Situ and In Vitro. \u003cem\u003eInt. J. Mol. Sci.\u003c/em\u003e \u003cstrong\u003e24\u003c/strong\u003e, 16518 (2023).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8211535/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8211535/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAlthough aneurysm pulsation \u0026ndash; or wall motion \u0026ndash; has been studied as a potential criterion to identify aneurysms prone to rupture, factors affecting this pulsation are not well understood. The purpose of this study was to test in vitro whether external \u0026ndash; \u0026ldquo;intracranial\u0026rdquo; \u0026ndash; pressure and/or parent vessel curvature impacted aneurysm pulsation and how.\u003c/p\u003e \u003cp\u003eIn this study, time-resolved CT angiography was used to detect and quantify volume pulsation of silicon aneurysm models using a test bench that could reproduce pulsatile flow within these models. A hermetic pressure box allowed us to test a range of external pressure on a simplified straight aneurysm model. For the second part, four silicon aneurysm models were custom made with varying curve radiuses at the aneurysm neck.\u003c/p\u003e \u003cp\u003eResults show that in a simplified in vitro setting an increase in external \u0026ndash; \u0026ldquo;intracranial\u0026rdquo; \u0026ndash; pressure leads to a decrease in pulsation amplitude and vice versa, and that the parent vessel curvature is not correlated with pulsation amplitude.\u003c/p\u003e","manuscriptTitle":"Intracranial aneurysms: in vitro study of “intracranial” pressure and parent vessel curvature as potential modifiers of aneurysm pulsation amplitude","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-20 10:30:11","doi":"10.21203/rs.3.rs-8211535/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"357fb3f7-b557-49d5-8fdc-b7404a827562","owner":[],"postedDate":"February 20th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":63216729,"name":"Health sciences/Diseases"},{"id":63216731,"name":"Physical sciences/Engineering"},{"id":63216732,"name":"Health sciences/Medical research"},{"id":63216733,"name":"Health sciences/Neurology"},{"id":63216734,"name":"Biological sciences/Neuroscience"}],"tags":[],"updatedAt":"2026-04-14T08:56:29+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-20 10:30:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8211535","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8211535","identity":"rs-8211535","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}