http://repub.eur.nl/res/aut/10649/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/28531/ 2010-05-01T00:00:00Z Aim: The purpose of this study was to define the in-vitro and in-vivo effects of intracoronary enhancement on the absolute density values of coronary plaques during multislice computed tomography. Methods: We studied seven ex-vivo left coronary artery specimens surrounded by olive oil and filled with isotonic saline and four solutions with decreasing dilutions of contrast material: control (isotonic saline), 1/200, 1/80, 1/50, and 1/20. The multislice computed tomography protocol was: slice/collimation 32 × 2 × 0.6 mm and rotation time 330 ms. The attenuation (Hounsfield units) value of atherosclerotic plaques was measured for each dilution in lumen, plaque (noncalcified coronary wall thickening), calcium, and surrounding oil. In-vivo assessment was performed in 12 patients (nine men; mean age 58.7 ± 9.9 years) who underwent two subsequent multislice computed tomography scans (arterial and delayed) after intravenous administration of a single bolus of contrast material. The attenuation values of lumen and plaques during arterial and delayed computed tomography were compared. The results were compared with one-way analysis of variance and correlated with Pearson's test. Results: Mean lumen (45 ± 38-669 ± 151 HU) and plaque (11 ± 35-101 ± 72 HU) attenuation differed significantly (P < 0.001) among the different dilutions. The attenuation of lumen and plaque of coronary plaques showed moderate correlation (r = 0.54, P < 0.001). The mean attenuation value in vivo for the arterial and delayed phase scans differed significantly (P < 0.001) for lumen (325 ± 70 and 174 ± 46 HU, respectively) and plaque (138 ± 71 and 100 ± 52 HU, respectively). Conclusion: Coronary plaque attenuation values are significantly modified by differences in lumen contrast densities both ex vivo and in vivo. This should be taken into account when considering the distinction between lipid and fibrous plaques. http://repub.eur.nl/res/pub/28700/ 2010-03-01T00:00:00Z Objectives: The aim of this study was to investigate the feasibility of using quantitative differential echogenicity to monitor the in vivo absorption process of a drug-eluting poly-l-lactic-acid (PLLA) bioabsorbable stent (BVS, Abbott Vascular, Santa Clara, CA). Background: A new bioabsorbable, balloon-expanded coronary stent was recently evaluated in a first-in-man study. Little is known about the absorption process in vivo in diseased human coronary arteries. Methods: In the ABSORB (Clinical Evaluation of the BVS everolimus eluting stent system) study, 30 patients underwent treatment with the BVS coronary stent system and were examined with intracoronary ultrasound (ICUS) after implantation, at 6 months and at 2-year follow-up. Quantitative ICUS was used to measure dimensional changes, and automated ICUS-based tissue composition software (differential echogenicity) was used to quantify plaque compositional changes over time in the treated regions. Results: The BVS struts appeared as bright hyperechogenic structures and showed a continuous decrease of their echogenicity over time, most likely due to the polymer degradation process. In 12 patients in whom pre-implantation ICUS was available, at 2 years the percentage-hyperechogenic tissue was close to pre-implantation values, indicating that the absorption process was either completed or the remaining material was no longer differentially echogenic from surrounding tissues. Conclusions: Quantitative differential echogenicity is a useful plaque compositional measurement tool. Furthermore, it seems to be valuable for monitoring the absorption process of bioabsorbable coronary stents made of semi-crystalline polymers. http://repub.eur.nl/res/pub/24079/ 2009-12-01T00:00:00Z Objectives and background: Quantitative analysis of intracoronary optical coherence tomography (OCT) image data (QOCT) is currently performed by a time-consuming manual contour tracing process in individual OCT images acquired during a pullback procedure (frame-based method). To get an efficient quantitative analysis process, we developed a fully automatic three-dimensional (3D) lumen contour detection method and evaluated the results against those derived by expert human observers. Methods: The method was developed using Matlab (The Mathworks, Natick, MA). It incorporates a graphical user interface for contour display and, in the selected cases where this might be necessary, editing. OCT image data of 20 randomly selected patients, acquired with a commercially available system (Lightlab imaging, Westford, MA), were pulled from our OCT database for validation. Results: A total of 4,137 OCT images were analyzed. There was no statistically significant difference in mean lumen areas between the two methods (5.03 ± 2.16 vs. 5.02 ± 2.21 mm2; P = 0.6, human vs. automated). Regression analysis showed a good correlation with an r value of 0.99. The method requires an average 2-5 sec calculation time per OCT image. In 3% of the detected contours an observer correction was necessary. Conclusion: Fully automatic lumen contour detection in OCT images is feasible with only a select few contours showing an artifact (3%) that can be easily corrected. This QOCT method may be a valuable tool for future coronary imaging studies incorporating OCT. http://repub.eur.nl/res/pub/24726/ 2009-09-01T00:00:00Z BACKGROUND: Coronary atherosclerosis is a dynamic process, which progresses differently in coronary segments containing noncalcified or calcified plaques. This may have implications for the study of the effects of therapy on progression/regression. OBJECTIVE: To test this hypothesis, we performed a post-hoc analysis on data of a randomized trial in which perindopril treatment was compared with placebo on progression/regression of atherosclerosis with regard to the degree of calcification. METHODS AND RESULTS: The intracoronary ultrasound data of 118 patients, who were enrolled in the multicentre, double-blinded randomized trial (PERSPECTIVE), were analysed. Vessel, lumen and plaque areas were measured in 711 5-mm-long matched coronary segments (perindopril 360, placebo 351). Each individual intracoronary ultrasound cross-section was binary labelled for the presence of calcium (yes/no), and the degree of calcium was assessed as a percentage of length. The segments were classified into three groups: 0-25, 25-50 and 50-100% (percentage of length) calcification. Coronary plaques with no or little calcium (0-25%) regressed on perindopril and did not change on placebo (-0.33±1.74 vs. -0.03±1.66, respectively; P=0.04). Plaques containing moderate calcium (group 25-50%) did not change and plaques with severe amounts of calcification (group 50-100%) equally progressed. CONCLUSION: Noncalcified plaques may be amenable to regression with ACE inhibitor treatment. The method, which considers the amount of calcium content in a plaque, may lead to new insights for quantitative analysis of the effects of therapy in progression/regression studies of atherosclerosis. http://repub.eur.nl/res/pub/25278/ 2009-03-01T00:00:00Z http://repub.eur.nl/res/pub/30459/ 2008-08-01T00:00:00Z Objective: This study aims to examine observer-related variability of quantitative optical coherence tomography (OCT) derived measurements from both in vitro and in vivo pullback data. Background: Intravascular OCT is a new imaging modality using infrared light and offering 10 times higher image resolution (15 μm) compared to intravascular ultrasound. The quantitative analysis of in vivo intracoronary OCT imaging is complicated by the presence of blood, motion artifacts and the large quantity of information that has to be processed. Methods: We developed a standardized, automated quantification process for intracoronary OCT pullback data with inter-observer variability assessed both in vitro by using postmortem human coronary arteries and in vivo by studying simple and complex coronary pathology and outcomes following stent implantation. The consensus between measurements by two observers was analyzed using the intraclass and interclass correlation coefficient and the reliability coefficients. Bland-Altman plots were generated to assess the relationship between variability and absolute measurements. Results: In vitro OCT assessment was performed in nine postmortem coronary arteries. The time needed for semiautomated contour detection of a 15-mm long coronary segment was ∼40 min. The absolute and relative difference between lumen area measurements derived from two observers was low [0.02 ± 0.10 mm2; (0.3 ± 0.5)% respectively] with excellent correlation confirmed by linear regression analysis (R2= 0.99; P < 0.001). Similarly, in vivo measurements demonstrated a high correlation with the main source of inter-observer variation occurring as a result of coronary dissection and motion artifact. The absolute and relative difference between measurements were 0.11 ± 0,33 mm2(1.57 ± 0.05)% for lumen area (R2= 0.98; P < 0.001), 0.17 ± 0.68 mm2(1.44 ± 0.08)% for stent area (R2= 0.94; P < 0.001), and 0.26 ± 0.72 mm2(14.05 ± 0.37)% for neointimal area (R2= 0.78; P < 0.001). Conclusions: Highly accurate computer-assisted quantitative analysis of intracoronary OCT pullbacks is feasible with low inter-observer variability. The presented approach allows for observer independent analysis of detailed vessel structures, and may be a valuable tool for future longitudinal studies incorporating OCT, http://repub.eur.nl/res/pub/29140/ 2008-05-01T00:00:00Z BACKGROUND: Noninvasive assessment of coronary atherosclerotic plaque may be useful for risk stratification and treatment of atherosclerosis. MATERIALS AND METHODS: We studied 47 patients to investigate the accuracy of coronary plaque volume measurement acquired with 64-slice multislice computed tomography (MSCT), using newly developed quantification software, when compared with quantitative intracoronary ultrasound (QCU). Quantitative MSCT coronary angiography (QMSCT-CA) was performed to determine plaque volume for a matched region of interest (regional plaque burden) and in significant plaque defined as a plaque with ≥50% area obstruction in QCU, and compared with QCU. Dataset with image blurring and heavy calcification were excluded from analysis. RESULTS: In 100 comparable regions of interest, regional plaque burden was highly correlated (coefficient r = 0.96; P < 0.001) between QCU and QMSCT-CA, but QMSCT-CA overestimated the plaque burden by a mean difference of 7 ± 33 mm (P = 0.03). In 76 significant plaques detected within the regions of interest, plaque volume determined by QMSCT-CA was highly correlated (r = 0.98; P < 0.001) with a slight underestimation of 2 ± 17 mm (P = not significant) when compared with QCU. Calcified and mixed plaque volume was slightly overestimated by 4 ± 19 mm (P = ns) and noncalcified plaque volume was significantly underestimated by 9 ± 11 mm (P < 0.001) with QMSCT-CA. Overall, the limits of agreement for plaque burden/volume measurement between QCU and QMSCT-CA were relatively large. Reproducibility for the measurements of regional plaque burden with QMSCT-CA was good, with a mean intraobserver and interobserver variability of 0% ± 16% and 4% ± 24%, respectively. CONCLUSIONS: Quantification of coronary plaque within selected proximal or middle coronary segments without image blurring and heavy calcification with 64-slice CT was moderately accurate with respect to intravascular ultrasound and demonstrated good reproducibility. Further improvement in CT resolution is required for more reliable measurement of coronary plaques using quantification software. http://repub.eur.nl/res/pub/36954/ 2007-12-01T00:00:00Z Objective: To validate automated and quantitative three-dimensional analysis of coronary plaque composition using intracoronary ultrasound (ICUS). Background: ICUS displays different tissue components based on their acoustic properties in 256 grey-levels. We hypothesised that computer-assisted image analysis (differential echogenicity) would permit automated quantification of several tissue components in atherosclerotic plaques. Methods and Results: Ten 40-mm-long left anterior descending specimens were excised during autopsy of which eight could be successfully imaged by ICUS. Histological sections were taken at 5 mm intervals and analyzed. Since most of the plaques were calcified and having a homogeneous appearance, one specimen with a more heterogeneous composition was further examined: at each interval of 5 mm, 15 additional sections (every 100 μm) were evaluated. Plaques were scored for echogenicity against the adventitia: brighter (hyperechogenic) or less bright (hypoechogenic). Areas of hypoechogenicity correlated with the presence of smooth muscle cells. Areas of hyperechogenicity correlated with presence of collagen, and areas of hyperechogenicity with acoustic shadowing correlated with calcium. None of these comparisons showed statistical significant differences. Conclusion: This ex vivo feasibility study shows that automated three-dimensional differential echogenicity analysis of ICUS images allows identification of different tissue types within atherosclerotic plaques. This technology may play a role as an additional tool in longitudinal studies to trace possible changes in plaque composition. http://repub.eur.nl/res/pub/36441/ 2007-07-01T00:00:00Z Attenuation variability (measured in Hounsfield Units, HU) of human coronary plaques using multislice computed tomography (MSCT) was evaluated in an ex vivo model with increasing convolution kernels. MSCT was performed in seven ex vivo left coronary arteries sunk into oil followingthe instillation of saline (1/∞) and a 1/50 solution of contrast material (400 mgI/ml iomeprol). Scan parameters were: slices/ collimation, 16/0.75 mm; rotation time, 375 ms. Four convolution kernels were used: b30f-smooth, b36f-medium smooth, b46f-medium and b60f-sharp. An experienced radiologist scored for the presence of plaques and measured the attenuation in lumen, calcified and noncalcified plaques and the surrounding oil. The results were compared by the ANOVA test and correlated with Pearson's test. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The mean attenuation values were significantly different between the four filters (p<0.0001) in each structure with both solutions. After clustering for the filter, all of the noncalcified plaque values (20.8±39.1, 14.2±35.8, 14.0±32.0, 3.2±32.4 HU with saline; 74.7±66.6, 68.2±63.3, 66.3±66.5, 48.5±60.0 HU in contrast solution) were significantly different, with the exception of the pair b36f-b46f, for which a moderate-high correlation was generally found. Improved SNRs and CNRs were achieved by b30f and b46f. The use of different convolution filters significantly modifief the attenuation values, while sharper filtering increased the calcified plaque attenuation and reduced the noncalcified plaque attenuation. http://repub.eur.nl/res/pub/37022/ 2007-05-01T00:00:00Z Background: The aim of this study was to investigate reproducibility end accuracy of computer-assisted coronary plaque measurements by multislice computed tomography coronary angiography (QMSCT-CA). Methods and Results: Forty-sight patients undergoing MSCT-CA end coronary arteriography for symptomatic coronary artery disease and quantitative intravascular ultrasound (IVUS, QCU) were examined. Two investigators performed the QMSCT-CA twice end e third investigator performed the QCU, all blinded for each other's results. There was no difference found for the matched region of interest (ROI) lengths (QCU 29.4 ± 13 mm vs. QMSCT-CA 29.6 ± 13 mm, P = 0.6; total length = 1,400 mm). The comparison of volumetric measurements showed (lumen QCU 267 ± 139 mm3vs. mean QMSCT-CA 177 ± 91 mm3, P < 0.001; vessel 454 ± 194 mm3vs. 398 ± 187 mm3, P < 0.001; and plaque 189 ± 93 mm3vs. 222 ± 121 mm3; investigator 1, P = 0.02; and investigator 2, P = 0.07) significant differences. Automated lumen detection was also applied for QMSCT-CA (218 ± 112 mm3, P < 0.001 vs. QCU). The Interinvestigator variability measurements for QMSCT-CA showed no significant differences. Conclusion: QMSCT-CA systematically underestimates absolute coronary lumen- and vessel dimensions when compared with QCU. However, repeated measurements of coronary plaque by QMSCT-CA showed no statistically significant differences, although, the outcome showed a scattered result. Automated lumen detection for QMSCT-CA showed improved results when compered with those of human investigators. http://repub.eur.nl/res/pub/37055/ 2007-03-01T00:00:00Z Coronary artery disease remains the leading cause of death in the Western world. Non-invasive coronary artery imaging challenges any diagnostic modality because the coronary arteries are small and tortuous, whereas cardiac contraction and respiration cause motion artifacts. Therefore, non-invasive coronary imaging requires high spatial and temporal resolution. This review discusses the feasible applications in coronary imaging of magnetic resonance imaging and multi-slice computed tomography (MSCT), which are currently the only non-invasive diagnostic modalities for direct coronary atherosclerosis imaging. Particular attention and focus is devoted to the potential indications and clinical impact of MSCT due to its fast development and the robust results recently reported. MSCT of the coronary arteries is a promising imaging modality for the assessment of the coronary lumen and wall. http://repub.eur.nl/res/pub/13701/ 2005-02-22T00:00:00Z BACKGROUND: The clinical impact of late incomplete stent apposition (ISA) for drug-eluting stents is unknown. We sought to prospectively investigate the incidence and extent of ISA after the procedure and at 6-month follow-up of paclitaxel-eluting stents in comparison with bare metal stents (BMS) and survey the clinical significance of ISA over a period of 12 months. METHODS AND RESULTS: TAXUS II was a randomized, double-blind study with 536 patients in 2 consecutive cohorts comparing slow-release (SR; 131 patients) and moderate-release (MR; 135 patients) paclitaxel-eluting stents with BMS (270 patients). This intravascular ultrasound (IVUS) substudy included patients who underwent serial IVUS examination after the procedure and at 6 months (BMS, 240 patients; SR, 113; MR, 116). The qualitative and quantitative analyses of ISA were performed by an independent, blinded core laboratory. More than half of the instances of ISA observed after the procedure resolved at 6 months in all groups. No difference in the incidence of late-acquired ISA was observed among the 3 groups (BMS, 5.4%; SR, 8.0%; MR, 9.5%; P=0.306), with a similar ISA volume (BMS, 11.4 mm3; SR, 21.7 mm3; MR, 8.5 mm3; P=0.18). Late-acquired ISA was the result of an increase of vessel area without change in plaque behind the stent. Predictive factors of late-acquired ISA were lesion length, unstable angina, and absence of diabetes. No stent thrombosis occurred in the patients diagnosed with ISA over a period of 12 months. CONCLUSIONS: The incidence and extent of late-acquired ISA are comparable in paclitaxel-eluting stents and BMS. ISA is a pure IVUS finding without clinical repercussions. http://repub.eur.nl/res/pub/4668/ 2004-01-01T00:00:00Z Intracoronary ultrasound (ICUS) is often used in studies evaluating new interventional techniques. It is important that quantitative measurements performed with various ICUS imaging equipment and materials are comparable. During evaluation of quantitative coronary ultrasound (QCU) software, it appeared that Boston Scientific Corporation (BSC) 30 MHz catheters connected to a Clearview ultrasound console showed smaller dimensions of an in vitro phantom model than expected. In cooperation with the manufacturer the cause of this underestimation was determined, which is described in this paper, and the QCU software was extended with an adjustment. Evaluation was performed by performing in vitro measurements on a phantom model consisting of four highly accurate steel rings (perfect reflectors) with diameters of 2, 3, 4 and 5 mm. Relative differences (unadjusted) of the phantom were respectively: 15.92, 13.01, 10.10 and 12.23%. After applying the adjustment: -0.96, -1.84, -1.35 and -1.43%. In vivo measurements were performed on 24 randomly selected ICUS studies. These showed differences for not adjusted vs. adjusted measurements of lumen-, vessel- and plaque volumes of -10.1 +/- 1.5, -6.7 +/- 0.9 and -4.4 +/- 0.6%. An off-line adjustment formula was derived and applied on previous numerical QCU output data showing relative differences for lumen- and vessel volumes of 0.36 +/- 0.51 and 0.13 +/- 0.31%. 30 MHz BSC catheters connected to a Clearview ultrasound console underestimate vessel dimensions. This can retrospectively be adjusted within QCU software as well as retrospectively on numerical QCU data using a mathematical model.