Reproducibility of serial optical coherence tomography measurements for lumen area and plaque components in humans (The CLI-VAR [Centro per la Lotta Contro l'Infarto-variability] II study).

Frequency-domain optical coherence tomography (FD-OCT) is a promising intracoronary imaging technique to study atherosclerosis. Indeed, its unprecedented spatial resolution allows the assessment of fibrous cap thickness, lipid pool and features of plaque vulnerability. Aim of this study was to determine the reproducibility of the in vivo FD-OCT measurements of lumen area and plaque components in serial studies. Twenty-six patients undergoing FD-OCT assessment of intermediate lesion during coronary angiography were included in this study. FD-OCT pullbacks were acquired twice from the same coronary segment at interval of 5 min without additional intervention and analyzed off-line at an independent imaging core laboratory. Lumen diameter (LD), lumen area (LA), fibrous cap (FC) thickness and lipid pool (LP) arc extension measurements were compared in 440 matched frames. Both the per-segment and per-frame analyses showed excellent correlation coefficients for the inter-pullback comparisons for all parameters explored (R > 0.95 and p < 0.001 in all cases). Accordingly, the Bland-Altman estimates of bias showed non-significant differences in the inter-pullback comparisons at all levels. Per-frame analysis showed a slightly variations of LA in 45.8% of cases with changes greater than 2% likely related to different phases of cardiac cycle. Nevertheless, nor FC thickness or circumferential arc of LP were affected by LA changes during serial FD-OCT acquisition. This study showed an excellent reproducibility of lumen and plaque component measurements obtained with FD-OCT in vivo. Thus, this intracoronary imaging technique could be used to assess atherosclerosis progression and describe accurate plaque evolution in repeated serial studies.

Identification and quantification of macrophage presence in coronary atherosclerotic plaques by optical coherence tomography.

AIMS: Vulnerable plaques are characterized by a high macrophage content. We investigated the optical coherence tomography (OCT) capability of identifying coronary plaque macrophage presence using tissue property indexes. METHODS AND RESULTS: Fifteen epicardial coronary arteries were imaged by OCT and subsequently analysed by histology. Correlating OCT-histological sections were identified and regions of interest (ROIs) were selected on both atherosclerotic plaques and normal appearing vessel tracts. OCT-derived tissue property indexes named normalized standard deviation (NSD), signal attenuation, and granulometry index were applied on ROIs to identify inflamed ROIs defined as a macrophage percentage >10 by histology. Forty-three paired samples (OCT frame and histology section) were considered suitable as ROIs for analysis. Eleven out of 43 ROIs were considered inflamed and the remaining 32 ROIs were non-inflamed on the basis of histological count of macrophage percentage. All OCT-derived tissue property indexes were positively correlated with macrophage percentage (P = 0.0001 for all). Receiver operating characteristic curve analysis showed that NSD, granulometry index, and signal attenuation had a significant area under the curve (area = 0.906, 0.804, and 0.793, respectively). A two-step algorithm requiring to first apply NSD with a cut-off value of 0.0570 followed by granulometry index was able to identify an inflamed ROI with a sensitivity of 100% and a specificity of 96.8%. CONCLUSION: OCT was able to identify and quantify macrophage presence in coronary artery specimens using tissue property indexes. NSD and granulometry index showed the highest accuracy in identifying a significant plaque inflammation, especially if used together in a two-step algorithm.

Reproducibility of the Carpet View system: a novel technical solution for display and off line analysis of OCT images.

The optical coherence tomography (OCT) evaluation of the stent anatomy requires the inspection of sequential cross section (CS). However stent coils cannot be appreciated in the conventional format as the OCT CS simply display stent struts, that are poorly representative of the stent architecture. The aim of the present study was to validate a new software (Carpet View), which unfolds the stented segment, reconstructing it as an open structure and displaying the stent meshwork. 21 patients were studied with frequency domain OCT after the deployment of different stents: seven bio-absorbable scaffolds (Dream), seven bare metal stent (Vision/Multilink8), seven drug eluting stent (Cre8). Conventional CS reconstructions were post-processed with the Carpet View software and analyzed by the same reader twice (intra-observer variability) and by two different readers (inter-observer variability). A small average difference in the number of all struts was obtained with the two methods (conventional vs carpet view reconstruction). Using the carpet view, high intra-observer and inter-observer correlations were found for the number of struts obtained in each coil. The Pearson correlation values were 0.98 (p = 0.0001) and 0.96 (p = 0.0001) respectively. The same number of coils was found when analyses were repeated by the same reader or by a different reader whilst mild differences in the count of stent junctions were reported. The Carpet View can be used to address the stent geometry with high reproducibility. This approach enables the matching of the same stent portion during serial time points and promises to improve the stent assessment.

Methodology for fully automated segmentation and plaque characterization in intracoronary optical coherence tomography images.

Optical coherence tomography (OCT) is a light-based intracoronary imaging modality that provides high-resolution cross-sectional images of the luminal and plaque morphology. Currently, the segmentation of OCT images and identification of the composition of plaque are mainly performed manually by expert observers. However, this process is laborious and time consuming and its accuracy relies on the expertise of the observer. To address these limitations, we present a methodology that is able to process the OCT data in a fully automated fashion. The proposed methodology is able to detect the lumen borders in the OCT frames, identify the plaque region, and detect four tissue types: calcium (CA), lipid tissue (LT), fibrous tissue (FT), and mixed tissue (MT). The efficiency of the developed methodology was evaluated using annotations from 27 OCT pullbacks acquired from 22 patients. High Pearson's correlation coefficients were obtained between the output of the developed methodology and the manual annotations (from 0.96 to 0.99), while no significant bias with good limits of agreement was shown in the Bland-Altman analysis. The overlapping areas ratio between experts' annotations and methodology in detecting CA, LT, FT, and MT was 0.81, 0.71, 0.87, and 0.81, respectively.

Evaluation of friction of stainless steel and esthetic self-ligating brackets in various bracket-archwire combinations.

This study measured and compared the level of frictional resistance generated between stainless steel self-ligating brackets (Damon SL II, SDS Ormco, Glendora, Calif), polycarbonate self-ligating brackets (Oyster, Gestenco International, Göthenburg, Sweden), and conventional stainless steel brackets (Victory Series, 3M Unitek, Monrovia, Calif), and 3 different orthodontic wire alloys: stainless steel (Stainless Steel, SDS Ormco), nickel-titanium (Ni-Ti, SDS Ormco), and beta-titanium (TMA, SDS Ormco). All brackets had a.022-in slot, whereas the orthodontic wire alloys were tested in 3 different sections:.016,.017 x.025, and.019 x 0.025 in. Each of the 27 bracket and archwire combinations was tested 10 times, and each test was performed with a new bracket-wire sample. Both static and kinetic friction were measured on a custom-designed apparatus. All data were statistically analyzed (Kruskal-Wallis and Mann Whitney U tests). Stainless steel self-ligating brackets generated significantly lower static and kinetic frictional forces than both conventional stainless steel and polycarbonate self-ligating brackets, which showed no significant differences between them. Beta-titanium archwires had higher frictional resistances than stainless steel and nickel-titanium archwires. No significant differences were found between stainless steel and nickel-titanium archwires. All brackets showed higher static and kinetic frictional forces as the wire size increased.