3D‐printed, patient‐specific intracranial aneurysm models: From clinical data to flow experiments with endovascular devices

Pravdivtseva, Mariya; Peschke, Eva; Lindner, Thomas; Wodarg, Fritz; Hensler, Johannes; Gabbert, Dominik Daniel; Voges, Inga; Berg, Philipp; Barker, Alex J.; Jansen, Olav; Hövener, Jan‐Bernd

doi:10.1002/mp.14714

Cited by 22 publications

(10 citation statements)

References 48 publications

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“…The following steps were applied: 1) the vessel lumens were segmented from the 3D‐RA dataset (threshold‐based segmentation followed by marching cubes, MevisLab 3.0.1, MeVis Medical solution, Germany); 2) the resulting lumens were optimized for 3D printing by cutting all branches smaller than 1 mm in diameter (Meshmixer 3.5, Autodesk); and 3) an outer layer was added to form a vessel wall, and flow connectors (Fusion 360 2.0, Autodesk) were applied to integrate the models into a flow loop. The detailed protocol has been published elsewhere 28 …”

Section: Methodsmentioning

confidence: 99%

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Pseudo‐Enhancement in Intracranial Aneurysms on Black‐Blood MRI: Effects of Flow Rate, Spatial Resolution, and Additional Flow Suppression

Pravdivtseva

Gaidzik²,

Berg³

et al. 2021

Magnetic Resonance Imaging

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Background Vessel‐wall enhancement (VWE) on black‐blood MRI (BB MRI) has been proposed as an imaging marker for a higher risk of rupture and associated with wall inflammation. Whether VWE is causally linked to inflammation or rather induced by flow phenomena has been a subject of debate. Purpose To study the effects of slow flow, spatial resolution, and motion‐sensitized driven equilibrium (MSDE) preparation on signal intensities in BB MRI of patient‐specific aneurysm flow models. Study Type Prospective. Subjects/Flow Aneurysm Model/Virtual Vessels Aneurysm flow models based on 3D rotational angiography datasets of three patients with intracranial aneurysms were 3D printed and perfused at two different flow rates, with and without Gd‐containing contrast agent. Field Strength/Sequence Variable refocusing flip angle 3D fast‐spin echo sequence at 3 T with and without MSDE with three voxel sizes ((0.5 mm)3, (0.7 mm)3, and (0.9 mm)3); time‐resolved with phase‐contrast velocity‐encoding 3D spoiled gradient echo sequence (4D flow MRI). Assessment Three independent observers performed a qualitative visual assessment of flow patterns and signal enhancement. Quantitative analysis included voxel‐wise evaluation of signal intensities and magnitude velocity distributions in the aneurysm. Statistical Tests Kruskal–Wallis test, potential regressions. Results A hyperintense signal in the lumen and adjacent to the aneurysm walls on BB MRI was colocalized with slow flow. Signal intensities increased by a factor of 2.56 ± 0.68 (P < 0.01) after administering Gd contrast. After Gd contrast administration, the signal was suppressed most in conjunction with high flows and with MSDE (2.41 ± 2.07 for slow flow without MSDE, and 0.87 ± 0.99 for high flow with MSDE). A clear result was not achieved by modifying the spatial resolution . Data Conclusions Slow‐flow phenomena contribute substantially to aneurysm enhancement and vary with MRI parameters. This should be considered in the clinical setting when assessing VWE in patients with an unruptured aneurysm. Evidence Level 2 Technical Efficacy Stage 2

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Section: Methodsmentioning

confidence: 99%

“…The detailed protocol has been published elsewhere. 28 After printing, the models were submerged in an agarose gel with a 3% concentration of agar (Special ingredients Ltd, UK). The models are publicly available and can be downloaded at https://doi.…”

Section: Model Productionmentioning

confidence: 99%

Pseudo‐Enhancement in Intracranial Aneurysms on Black‐Blood MRI: Effects of Flow Rate, Spatial Resolution, and Additional Flow Suppression

Pravdivtseva

Gaidzik²,

Berg³

et al. 2021

Magnetic Resonance Imaging

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“…Second, it was simplified, e.g., by cutting branches smaller than 1 mm. Finally, the outer wall (3 mm thick) was added and models were equipped with flow connectors [ 28 ]. For further details the interested reader is referred to [ 27 ].…”

Section: Methodsmentioning

confidence: 99%

Luminal enhancement in intracranial aneurysms: fact or feature?—A quantitative multimodal flow analysis

et al. 2021

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Purpose Intracranial aneurysm (IA) wall enhancement on post-contrast vessel wall magnetic resonance imaging (VW-MRI) is assumed to be a biomarker for vessel wall inflammation and aneurysm instability. However, the exact factors contributing to enhancement are not yet clarified. This study investigates the relationship between luminal enhancement and intra-aneurysmal flow behaviour to assess the suitability of VW-MRI as a surrogate method for determining quantitative and qualitative flow behaviour in the aneurysm sac. Methods VW-MRI signal is measured in the lumen of three patient-specific IA flow models and compared with the intra-aneurysmal flow fields obtained using phase-contrast magnetic resonance imaging (PC-MRI) and computational fluid dynamics (CFD). The IA flow models were supplied with two different time-varying flow regimes. Results Overall, the velocity fields acquired using PC-MRI or CFD were in good agreement with the VW-MRI enhancement patterns. Generally, the regions with slow-flowing blood show higher VW-MRI signal intensities, whereas high flow leads to a suppression of the signal. For all aneurysm models, a signal value above three was associated with velocity values below three cm/s. Conclusion Regions with lower enhancements have been correlated with the slow and high flow at the same time. Thus, further factors like flow complexity and stability can contribute to flow suppression in addition to the flow magnitude. Nevertheless, VW-MRI can qualitatively assess intra-aneurysmal flow phenomena and estimate the velocity range present in the corresponding region.

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“…The flow setup proved to be stable over at least 3 h (details in Figure S1). A patient-specific aneurysm model was designed and 3D printed (Form 3, Formlabs Inc., Somerville, MA, USA) in-house [31] (Figure 1b). Aneurysm geometry was segmented from 3D rotational angiographic data of a patient with a 17.5-mm infraophthalmic extradural internal carotid artery (ICA) aneurysm.…”

Section: Flow Models and Circulation Setupmentioning

confidence: 99%

“…A mixture of methacrylic acid esters and a photoinitiator (Clear Photoreactive Resin, Formlabs Inc., Somerville, MA, USA) was used for 3D printing of an aneurysm model with a rigid wall. The inlet and outlet flow and A patient-specific aneurysm model was designed and 3D printed (Form 3, Formlabs Inc., Somerville, MA, USA) in-house [31] (Figure 1b). Aneurysm geometry was segmented from 3D rotational angiographic data of a patient with a 17.5-mm infraophthalmic extradural internal carotid artery (ICA) aneurysm.…”

Section: Flow Models and Circulation Setupmentioning

confidence: 99%

Influence of Spatial Resolution and Compressed SENSE Acceleration Factor on Flow Quantification with 4D Flow MRI at 3 Tesla

et al. 2022

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Four-dimensional (4D) flow MRI allows quantifying flow in blood vessels–non invasively and in vivo. The clinical use of 4D flow MRI in small vessels, however, is hampered by long examination times and limited spatial resolution. Compressed SENSE (CS-SENSE) is a technique that can accelerate 4D flow dramatically. Here, we investigated the effect of spatial resolution and CS acceleration on flow measurements by using 4D flow MRI in small vessels in vitro at 3 T. We compared the flow in silicon tubes (inner diameters of 2, 3, 4, and 5 mm) measured with 4D flow MRI, accelerated with four CS factors (CS = 2.5, 4.5, 6.5, and 13) and three voxel sizes (0.5, 1, and 1.5 mm3) to 2D flow MRI and a flow sensor. Additionally, the velocity field in an aneurysm model acquired with 4D flow MRI was compared to the one simulated with computational fluid dynamics (CFD). A strong correlation was observed between flow sensor, 2D flow MRI, and 4D flow MRI (rho > 0.94). The use of fewer than seven voxels per vessel diameter (nROI) resulted in an overestimation of flow in more than 5% of flow measured with 2D flow MRI. A negative correlation (rho = −0.81) between flow error and nROI were found for CS = 2.5 and 4.5. No statistically significant impact of CS factor on differences in flow rates was observed. However, a trend of increased flow error with increased CS factor was observed. In an aneurysm model, the peak velocity and stagnation zone were detected by CFD and all 4D flow MRI variants. The velocity difference error in the aneurysm sac did not exceed 11% for CS = 4.5 in comparison to CS = 2.5 for all spatial resolutions. Therefore, CS factors from 2.5–4.5 can appear suitable to improve spatial or temporal resolution for accurate quantification of flow rate and velocity. We encourage reporting the number of voxels per vessel diameter to standardize 4D flow MRI protocols.

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3D‐printed, patient‐specific intracranial aneurysm models: From clinical data to flow experiments with endovascular devices

Cited by 22 publications

References 48 publications

Pseudo‐Enhancement in Intracranial Aneurysms on Black‐Blood MRI: Effects of Flow Rate, Spatial Resolution, and Additional Flow Suppression

Pseudo‐Enhancement in Intracranial Aneurysms on Black‐Blood MRI: Effects of Flow Rate, Spatial Resolution, and Additional Flow Suppression

Luminal enhancement in intracranial aneurysms: fact or feature?—A quantitative multimodal flow analysis

Influence of Spatial Resolution and Compressed SENSE Acceleration Factor on Flow Quantification with 4D Flow MRI at 3 Tesla

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