Guide wire shadow assessed by shading index is reduced in sparse spring coil wire in optical coherence tomography
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ORIGINAL ARTICLE
Guide wire shadow assessed by shading index is reduced in sparse spring coil wire in optical coherence tomography Fumiaki Nakao • Tooru Ueda • Shigehiko Nishimura Hitoshi Uchinoumi • Masashi Kanemoto • Nobuaki Tanaka • Takashi Fujii
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Received: 18 March 2013 / Accepted: 7 May 2013 Ó Japanese Association of Cardiovascular Intervention and Therapeutics 2013
Abstract One of the major problems of a Fourier-domain optical coherence tomography (FD-OCT) is the guide wire (GW) shadow which disturbs precise coronary assessment. If two or more GWs are used in a bifurcation PCI, the GW shadow becomes larger. In FD-OCT, GWs were usually observed as a crescent shape, but GWs with the sparse spring coil were observed as either round or crescent shape. The measured angle making GW shadow of GW without the sparse spring coil was similar to its theoretical angle (30.4 ± 1.7° vs. 30.1 ± 0.7°, p = 0.21); however, the measured angle of GW with the sparse spring coil was significantly smaller than its theoretical angle (16.8 ± 4.8° vs. 28.7 ± 1.5°, p \ 0.01). For standardization of shadingeffect of GW, a virtual diameter of GW which was calculated from a measured angle, an actual diameter of GW, and a distance between an imaging catheter and GW was defined as the shading index. The shading index of GW with the sparse spring coil was significantly smaller than that of GW without the sparse spring coil (0.008 ± 0.002 vs. 0.014 ± 0.001, p \ 0.01). Shading indices of GWs with the sparse spring coil were smaller than their actual diameters. The sparse spring coil structure could contribute to the reduction of the GW shadow in FD-OCT. Also, we proposed the new and useful shading index to indicate the shading-effect of GW.
Introduction Fourier-domain optical coherence tomography (FD-OCT) and three-dimensional OCT (3D-OCT) are useful to confirm the relation between side branch orifice and stent struts, and the guide wire (GW) recrossing position during a bifurcation PCI [1–7]. The GW shadow becomes larger when two or more GWs are deployed in the same coronary artery, and therefore it becomes difficult to confirm the side branch orifice [5]. Although the GW shadow may be reduced by detaching the GW from the imaging catheter, namely, moving the GW close to the vessel wall, or by exchanging the GW for a more slender one, or by removing the GW, such an attempt does not always succeed in reducing the GW shadow. Some GWs have the sparse spring coil which the other many GWs do not have (Fig. 1a). We found by chance that the GW with the sparse spring coil showed strange image pattern in FD-OCT (Fig. 1b, c). GWs were usually observed as a crescent shape in FD-OCT; however, the GW with the sparse spring coil was observed as either a round or crescent shape. In this paper, the relationship between the sparse spring coil structure of GW, strange image pattern of the particular GW, and the reduction of the GW shadow in GWs with the sparse spring coil were investigated.
Keywords Guide wire shadow FD-OCT Sparse spring coil Shadin
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