Evaluation of guidewire path reproducibility

Abstract

The number of minimally invasive vascular interventions is increasing. In these interventions, a variety of devices are directed to and placed at the site of intervention. The device used in almost all of these interventions is the guidewire, acting as a monorail for all devices which are delivered to the intervention site. However, even with the guidewire in place, clinicians still experience difficulties during the interventions. As a first step toward understanding these difficulties and facilitating guidewire and device guidance, we have investigated the reproducibility of the final paths of the guidewire in vessel phantom models on different factors: user, materials and geometry. Three vessel phantoms (vessel diameters approximately 4 mm) were constructed having tortuousity similar to the internal carotid artery from silicon tubing and encased in Sylgard elastomer. Several trained users repeatedly passed two guidewires of different flexibility through the phantoms under pulsatile flow conditions. After the guidewire had been placed, rotational c-arm image sequences were acquired (9 in. II mode, 0.185 mm pixel size), and the phantom and guidewire were reconstructed (512(3), 0.288 mm voxel size). The reconstructed volumes were aligned. The centerlines of the guidewire and the phantom vessel were then determined using region-growing techniques. Guidewire paths appear similar across users but not across materials. The average root mean square difference of the repeated placement was 0.17 +/- 0.02 mm (plastic-coated guidewire), 0.73 +/- 0.55 mm (steel guidewire) and 1.15 +/- 0.65 mm (steel versus plastic-coated). For a given guidewire, these results indicate that the guidewire path is relatively reproducible in shape and position.

Figure 1

Vessel phantom. The tube length in the phantom is 143 mm, and the lumen diameter is 3.65 mm.

Figure 2

From left to right: Phantom A (lumen length 23 cm, lumen diameter 4.5 mm), Phantom B (lumen length 19.1 cm, lumen diameter 4.5 mm), Phantom C (lumen length 15.6 cm, lumen diameter 3.6 mm).

Figure 3

(a) Cumulative histogram of intra-user variations in plastic-coated guidewire insertions for the three phantoms (A, B, and C) [Eq. 5]. (b) Cumulative histogram of inter-user variations in plastic-coated guidewire insertions for phantoms A, B, and C [Eq. 5].

Figure 4

(a) Cumulative histogram of intra-user variations in steel guidewire paths for phantoms A, B and C [Eq. 8]. (b) Cumulative histograms of inter-user variations in steel guidewire insertions for phantoms A, B, and C [Eq. 8].

Figure 5

(a) Distance of ${\overline{g}}_{2,st}\left(j\right)$ to the vessel wall and the standard deviation σ_2,st(j) along the centerline for the steel guidewire in phantom B. (b) The average variation of the guidewire paths as a function of distance from the vessel wall for phantom B and phantoms A and C. As the guidewire path moves away from the vessel wall, the variation increases.