Wavelet analysis of RF IVUS signals enabled in vitro as well as in vivo detection of lipid-laden plaque. This method may be useful in assessing plaque vulnerability in patients with coronary artery disease.

Background-The thickness of the fibrous cap is a major determinant in the vulnerability of atherosclerotic plaque to rupture. It has been demonstrated that intravascular ultrasound (IVUS) backscatter from fibrous tissue is strongly dependent on the ultrasound beam angle of incidence. This study investigated the feasibility of using a new IVUS color mapping technique representing the angle-dependent echo-intensity variation to determine the thickness of the fibrous cap in atherosclerotic plaque. Methods and Results-Nineteen formalin-fixed noncalcified human atherosclerotic plaques from necropsy were imaged in vitro with a 30-MHz IVUS catheter. The IVUS catheter was moved coaxially relative to the plaque. The images showing maximum and minimum echo intensity of the plaque surface were selected to calculate the angle-dependent echo-intensity variation. A colorized representation of the echo-intensity variation in the plaque was obtained from the 2 IVUS images. A clearly bordered area with large variation in echo intensity was revealed for each plaque surface in the colorized IVUS image. The thickness (x, mm) of this area correlated significantly with that of fibrous cap (y, mm) measured from histologically prepared sections as yϭ1.05xϪ0. 01 (rϭ0.81, PϽ0.0001). Bland-Altman analysis also supported the reliability of this method (mean difference, 0.00Ϯ0.10 mm). Conclusions-This novel technique for color mapping the echo-intensity variation in IVUS provided an accurate representation of the thickness of the fibrous cap in atherosclerotic plaque. This method may be useful in assessing plaque vulnerability to rupture in atherosclerosis.

n-stent neointimal hyperplasia (INH) is the main cause of restenosis after stenting 1 and several mechanisms have been proposed as determinants of the degree of in-stent neointimal proliferation: the amount of residual plaque burden; 2 the degree of rupture or dissection of the vessel wall after balloon dilation; 3 the aggressiveness of the stent implantation technique; 4 the degree of overexpansion or oversizing of the balloon; 5,6 multiple stents; 7 high acute gain; 7,8 high inflation pressure; 7,9 length of the stenosis; 7 small reference diameter; 7 small stent size; 10,11 and stent design. 12-14 Among these reports, Garasic et al documented the effect of local stent geometry on INH in rabbit arteries, 13 but there are no reports on the role of local stent geometry in intimal hyperplasia in human coronary arteries in vivo.Intravascular ultrasound (IVUS) can visualize INH in vivo, so it was used in the present study to examine the relationship between the cross-sectional geometry of the post-deployment coronary stent and the degree of INH. Circulation Journal Vol.66, May 2002 Methods Patient SelectionTwenty-three patients (13 men, 10 women; 63±10 years old, range, 31-79 years) with coronary stents (13 Multilink, 10 GFX stents) were selected and underwent follow-up cardiac catheterization at approximately 6 months (mean, 6.5±1.1 months) after stent implantation between 1997 and 2000. Exclusion criteria included a stented left main coronary artery, extreme tortuosity of the lesions, additional cardiac events during the 6 months since implantation, lesions with calcification of more than a 90°arc, lesions with poor IVUS image quality because of significant dropout, artifact and/or non-uniform rotational distortion, lesions wedged with a IVUS catheter. All stents had been deployed with an expanded balloon pressure of 10 atm.The study was approved by the Institutional Review Board of Clinical Research of Yamaguchi University. All patients gave informed written consent before IVUS imaging. IVUS ImagingFollow-up IVUS images were obtained with a 3.2 or 2.6Fr short monorail imaging catheter (30MHz Ultracross  and/or 40 MHz Discovery  or Atlantis  /Boston Scientific, Natick, MA, USA). Therapeutic anticoagulation was achieved with 5,000 IU heparin iv. Intracoronary isosorbide dinitrate (1.0 mg) was administered just before IVUS imaging. The transducer was then advanced as distally as possible, after To establish the relationship between the cross-sectional geometry of the post-deployment stent and the degree of in-stent neointimal hyperplasia (INH), intravascular ultrasound (IVUS) was used to examine cross-sections of the coronary arteries from 23 patients with coronary stents 6 months after implantation. Stent cross-sectional area (Sa) and stent perimeter (Sp) from 200 stent cross-sections, and the stent radius (Sr) and thickness of INH (Id) of 2,880 radial axes, were measured, and the mean degree of roundness (Rd) of stent cross-section was calculated for each stent as Rd = 4 Sa / Sp 2 . The degree of deformity (Df...

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