Flow diverters: inter and intra-rater reliability of porosity and pore density measurements

Farzin, Behzad; Brosseau, Lucie; Jamali, Sarah; Salazkin, Igor; Jack, Andrew; Darsaut, T.E.; Raymond, Jean

doi:10.1136/neurintsurg-2014-011240

Cited by 11 publications

(11 citation statements)

References 26 publications

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“…In addition, the porosity and pore density in Table 1 are derived directly from the nominal device dimensions, and measurements of these variables from microphotographs may be subject to a 9% difference in porosity and 3 pores/mm 2 in pore density. 20…”

Section: Discussionmentioning

confidence: 99%

“…The porosity ranged from 49−82%, and the pore density from 5−36 pores/mm 2 . The porosity and pore density were not local variables measured from microphotographs of a device; 20 instead, these numbers were averaged throughout a device and derived directly from dimensions and parameters provided by the manufacturer using the following mathematical formulas: where n is the number of wire, d the wire size, D the device diameter, and p the pitch. The pitch is related to the braiding angle and device diameter by tanβ2=πDp The target braiding angle (β), typically between 120−130˚, is optimized to provide the most metal coverage or lowest porosity of a device, but is often different from the angle after deployment.…”

Section: Methodsmentioning

confidence: 99%

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In vitro digital subtraction angiographic evaluation of flow diverters in a patient-specific aneurysm

Jou

2017

Interv Neuroradiol

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Background The importance of both porosity and pore density of a flow diverter is well recognized in treatment of intracranial aneurysms; however, understanding of the effect of individual wire (wire number and size) is critical in improving device design and use. Methods A total of 10 multi-layered flow diverters with different wire numbers (32, 48, 56, and 72) and sizes (30, 35, and 40 µm) were implanted into identical patient-specific middle cerebral artery aneurysm models. Digital subtraction angiography was acquired at 30 f/s and X-ray signals at three selected regions of interest were compared to determine the amount of intra-aneurysmal flow. Results Flow reduction ranged from 19% for a high porosity (82%) and low pore density (5 pores/mm2) to nearly 80% for a low porosity (49%) and high pore density (36 pores/mm2). An increase in the wire number from 32 to 72 lowers intra-aneurysmal flow and redirects the flow jet; however, the effect of wire size is not observed. Conclusions In our in vitro angiographic study, flow jet is influenced by the wire number in a device qualitatively; quantitatively, intra-aneurysmal flow is affected by both the porosity and pore density. A 2.5 mm device performs better in flow diversion of a middle cerebral artery (MCA) aneurysm than a 3 mm device with the same wire size and wire number, but thicker wires do not lead to better flow diversion.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

In vitro digital subtraction angiographic evaluation of flow diverters in a patient-specific aneurysm

Jou

2017

Interv Neuroradiol

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“…1 Furthermore, automated or manual methods for measuring PD or porosity are not currently reliable. 14,24 Comparison between different devices using one isolated mechanical characteristic of the stent is therefore not appropriate.…”

Section: Discussionmentioning

confidence: 99%

“…11–13 Furthermore, there is no standardised and reliable method to measure flow diverter porosity and PD. 14 However, measuring the capacity of this new generation device to induce blood stasis may help the clinician to understand better the predictive factors related to the effectiveness and safety of these devices. The aim of this study was to propose a new bench test parameter (the pressure reduction coefficient (PRC); ξ ) in order to assess in one measure the global haemodynamic capacity of each flow diverter/disruptor to reduce flow.…”

Section: Introductionmentioning

confidence: 99%

The pressure reduction coefficient: A new parameter to assess aneurysmal blood stasis induced by flow diverters/disruptors

et al. 2016

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Background and purpose Pore density (PD), surface metal coverage (SMC) and the number of wires are all different parameters which can influence the efficacy of a flow disruptor/diverter. Nevertheless, the relative importance of a parameter to induce intra-aneurysmal blood stasis is still poorly evaluated. Therefore, comparison between devices based on a unique value is not reliable. The aim of this study was to propose a new bench top parameter (the pressure reduction coefficient (PRC; ξ)) in order to assess the global haemodynamic effect of each flow diverter/disruptor to slow flow. Methods Eight devices were tested in vitro during three different flow conditions. For the eight devices, the PRC was computed at different volumetric flow rates to characterise flow reduction. Comparison was made with SMC, PD and the number of wires. Results The PRC obtained for flow disruptors was on average 1.5 times more efficient in reducing flow compared to flow diverters. PD (mm2) ranged from 24 to 38 for flow diverters and did not independently correlate with the PRC. The SMC of flow diverters ranged from 25% to 70%, and ranged from 20% to 100% for flow disruptors, without independent correlation to the PRC. The number of wires ranged from 48 to 96 for the flow diverters and did not correlate independently to the PRC. Conclusion There were no direct correlations between individual device characteristics and the PRC, suggesting a multifaceted and interrelating association of the overall design of each implant. Hence, the PRC could be used as a simple, reliable parameter to assess the overall capacity of flow disruptors/diverters to induce intra-aneurysmal blood stasis.

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“…Fourth, because OsR and NR are independent of the FD device used; the effect of optimized FD-deployment strategies, such as compacting the device at the aneurysm neck 18 cannot be predicted by either OsR or NR. Fifth, as demonstrated by Farzin et al, 37 measurements of MCR and pore-density could be subjective and depend on the operator. Thus, our MCR and pore-density measurements might not represent actual values but provide a good estimate for each case, as shown by our experimental validation in the Supplementary Material.…”

Section: Discussionmentioning

confidence: 99%

Ostium Ratio and Neck Ratio Could Predict the Outcome of Sidewall Intracranial Aneurysms Treated with Flow Diverters

Paliwal¹,

Tutino

Shallwani

et al. 2019

AJNR Am J Neuroradiol

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Background and Purpose: To identify the potential for incomplete occlusion of intracranial aneurysms treated by flow-diverters (FD), we investigated if aneurysm ostium size in relation to parent artery size affects angiographic outcomes of FD-treated sidewall aneurysms. Materials and Methods: FD-treated sidewall aneurysms were divided into “occluded” and “residual” (incomplete occlusion) groups based on 6-month angiographic follow-up. We calculated ostium ratio (OsR), a new parameter defined as the aneurysm ostium surface area versus the circumferential surface area of the parent artery. As a two-dimensional surrogate, we also calculated neck ratio (NR), defined as clinical aneurysm neck diameter versus parent artery diameter from pretreatment two-dimensional DSA. We compared the performance of these ratios with existing aneurysm morphometrics (size, neck-diameter, volume, aspect ratio, size ratio, undulation index, non-sphericity index, ellipticity index, bottleneck factor, aneurysm angle, parent vessel angle) and FD-related parameters (metal coverage rate, pore-density). Statistical tests and receiver-operating characteristic (ROC) analyses were performed to identify significantly different parameters between the two groups and test their predictive performances. Results: Sixty-three FD-treated aneurysms were included: 46 occluded and 17 residual. OsR and NR were significantly higher in the residual group than the occluded group (p<0.001 and p=0.02, respectively), whereas all other parameters showed no statistical difference. As discriminating parameters for occlusion, OsR and NR achieved an area under the curve of 0.912 (95%CI=0.838–0.985) and 0.707 (95%CI=0.558–0.856), respectively. Conclusion: High OsR and NR could predict incomplete occlusion of FD-treated sidewall aneurysms. NR can be easily calculated by interventionists to predict FD-treatment outcomes.

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Flow diverters: inter and intra-rater reliability of porosity and pore density measurements

Abstract: Without standardization, the porosity of different devices cannot reliably be compared because use of different methods or different observers substantially changes results. Pore density seems to be more reliably measured than porosity.

Cited by 11 publications

References 26 publications

In vitro digital subtraction angiographic evaluation of flow diverters in a patient-specific aneurysm

In vitro digital subtraction angiographic evaluation of flow diverters in a patient-specific aneurysm

The pressure reduction coefficient: A new parameter to assess aneurysmal blood stasis induced by flow diverters/disruptors

Ostium Ratio and Neck Ratio Could Predict the Outcome of Sidewall Intracranial Aneurysms Treated with Flow Diverters

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