Article Figures & Data
Figures
- Fig 1.
A, Representative image of a 4.25 × 20 mm Pipeline device inserted into plastic tubes of 0.5-mm incremental diameters. Variation in the degree of metal coverage is apparent. The configuration of cells is schematically depicted above the construct. Metal coverage can be calculated directly on the basis of measurements of the long and short diagonals of the rhombus and the diameter of each strand (30-μm), according to the formula above. Minimum coverage is seen when θ = 90°, corresponding to a square cell configuration. B, Scatterplot of tube diameter versus metal coverage for various device and “artery” combinations. All functions have a parabolic configuration. Note that absolute coverage values are higher for smaller diameter devices at each given tube diameter. The overall single-device coverage is, therefore, likely to be somewhat smaller for appropriately sized devices deployed in larger vessels.
- Fig 2.
Consequences of device oversizing and the proposed solution. A, A model of a fusiform aneurysm with 3.0- and 5.0-mm landing zones, bridged by a single 5 × 20 mm device. A transition zone (TZ) of minimum coverage is created as the device is constrained from its fully opened state into the 3-mm landing zone. Despite adequate length of the “landing zone” at the 3.0-mm end, the “shape memory” of the transition zone, TZ, nevertheless produces a “gap” where the device remains unapposed to the inner wall of the tube. B, To address these issues, 2 devices are required, each of which is appropriately sized for its recipient artery. The first 3.0-mm device is deployed from the 3.0-mm-diameter vessel into the 5-mm recipient vessel, following which a second 5.0-mm diameter device is telescoped into the first, with the 5.0-mm device anchored into its 5.0-mm vessel. Thus, the transition zone, TZ, is shifted outside the aneurysm, while the aneurysmal segment receives the benefit of double-coverage.
- Fig 3.
Manual segmentation method of determining metal coverage. A, Photographic image of a 3.75-mm device deployed within a 3.5-mm plastic tube. A translucent fiberoptic rod is placed inside the construct to eliminate visualization of the “back” portion of the braids. B, Curved lines, with thickness corresponding to 30 μm (calibrated to a ruler placed alongside the construct) are traced along each braid. C, The underlying image is removed, leaving a black and white segmentation image. D, With the ImageJ measurement tool, the proportion of black pixels within a given rectangular area corresponds to the percentage of metal coverage, according to the formula listed in the “Materials and Methods” section.
- Fig 4.
Overlapping segmentation images illustrating patterns of double coverage with identical-diameter (A–C) and different-diameter devices (D–F). It can be readily seen from Figs A–C that 2 overlapping 3.75-mm devices can result in a wide range of coverage, depending on the exact alignment of device braids of identical pitch relative to each other. In contrast, an overlap of 3.75- and 4.25-mm devices (Figs D–F), because of the different braid pitch for each device, produces a more consistent overall coverage pattern, regardless of the particular phase of overlap.
- Fig 5.
Photographs of overlapping 3.75- and 4.25-mm-diameter devices deployed in a 3.5-mm tube. Visual appreciation of nonuniform coverage for two 3.75-mm devices: Area A shows near-perfect overlap of both device braids, with no practical increase in coverage for this segment, whereas the braid phase shift in area B produces significantly higher coverage. In contrast, overlap of 3.75- and 4.25-mm devices yields a more consistent pattern, with less potential variation in coverage values. The absolute value of such coverage is between the minimal and maximal potential values expected from overlapping two 3.75-mm devices.
- Fig 6.
Example of triple coverage with 3 different-diameter stents. Note that despite overall relatively high coverage, areas of lower coverage and significantly larger pore size remain (white rectangle).
Tables
- Table 1:
Correlation between manual and estimated coverage values for the construct pictured in Fig 5a
3.5-mm-Vessel Manual Segmentation Manual Estimated 3.75 PED 22% 3.75 + 4.25 PED 36%–37% 36%–37% 4.25 PED 18%–19% ↵a Manual segmentation was done by tracing curved lines over each braid in the double-coverage area and comparing the result with values estimated by overlapping segmented images from separate 3.75- and 4.25-mm devices individually deployed within a 3.5-mm artificial vessel. The 2 methods are in excellent agreement.
- Table 2:
The range of coverage values expected from overlap of various size devices in tubes of 3, 3.5, 4, and 4.5-mm diametersa
3-mm Vessel 3.25 3.75 4.25 4.75 3.25 30%–47% 30%–40% 31%–37% 34%–37% 3.75 20%–37% 30%–37% 30%–35% 4.25 21%–35% 31%–34% 4.75 20%–36% 3.5-mm Vessel 3.75 4.25 4.75 3.75 24%–41% 36%–37% 33%–34% 4.25 22%–36% 31%–32% 4.75 18%–31% 4-mm Vessel 3.75 4.25 4.75 3.75 38%–46% 37%–39% 36%–37% 4.25 21%–35% 29%–33% 4.75 22%–32% 4.5-mm Vessel 4.25 4.75 4.25 36%–57% 40%–44% 4.75 25%–34% ↵a Note that the broadest range of coverage for each device/artery combination is always observed during overlap of identical-diameter devices. Use of devices with progressively different diameters produces correspondingly narrower ranges of coverage (due to the more consistent misregistration of strands arising from the differing pitches imposed on devices of different diameters constrained within a given diameter vessel), with absolute coverage values falling in-between the potential minima and maxima expected from overlap of identical devices.
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