Jouke Dijkstra

Consensus standards for acquisition, measurement, and reporting of intravascular optical coherence tomography studies: a report from the International Working Group for Intravascular Optical Coherence Tomography Standardization and Validation.

OBJECTIVES The purpose of this document is to make the output of the International Working Group for Intravascular Optical Coherence Tomography (IWG-IVOCT) Standardization and Validation available to medical and scientific communities, through a peer-reviewed publication, in the interest of improving the diagnosis and treatment of patients with atherosclerosis, including coronary artery disease. BACKGROUND Intravascular optical coherence tomography (IVOCT) is a catheter-based modality that acquires images at a resolution of ~10 μm, enabling visualization of blood vessel wall microstructure in vivo at an unprecedented level of detail. IVOCT devices are now commercially available worldwide, there is an active user base, and the interest in using this technology is growing. Incorporation of IVOCT in research and daily clinical practice can be facilitated by the development of uniform terminology and consensus-based standards on use of the technology, interpretation of the images, and reporting of IVOCT results. METHODS The IWG-IVOCT, comprising more than 260 academic and industry members from Asia, Europe, and the United States, formed in 2008 and convened on the topic of IVOCT standardization through a series of 9 national and international meetings. RESULTS Knowledge and recommendations from this group on key areas within the IVOCT field were assembled to generate this consensus document, authored by the Writing Committee, composed of academicians who have participated in meetings and/or writing of the text. CONCLUSIONS This document may be broadly used as a standard reference regarding the current state of the IVOCT imaging modality, intended for researchers and clinicians who use IVOCT and analyze IVOCT data.

Sirolimus-eluting stents versus bare-metal stents in patients with ST-segment elevation myocardial infarction: 9-month angiographic and intravascular ultrasound results and 12-month clinical outcome results from the MISSION! Intervention Study.

OBJECTIVES Our purpose was to evaluate the efficacy and safety of drug-eluting stents in the setting of primary percutaneous coronary intervention for ST-segment elevation myocardial infarction (STEMI). BACKGROUND There is inconsistent and limited evidence about the efficacy and safety of drug-eluting stents in STEMI patients. METHODS A single-blind, single-center, randomized study was performed to compare bare-metal stents (BMS) with sirolimus-eluting stents (SES) in 310 STEMI patients. The primary end point was in-segment late luminal loss (LLL) at 9 months. Secondary end points included late stent malapposition (LSM) at 9 months as determined by intravascular ultrasound imaging and clinical events at 12 months. RESULTS In-segment LLL was 0.68 +/- 0.57 mm in the BMS group and 0.12 +/- 0.43 mm in the SES group with a mean difference of 0.56 mm, 95% confidence interval 0.43 to 0.68 mm (p < 0.001). Late stent malapposition at 9 months was present in 12.5% BMS patients and in 37.5% SES patients (p < 0.001). Event-free survival at 12 months was 73.6% in BMS patients and 86.0% in SES patients (p = 0.01). The target-vessel-failure-free survival was 84.7% in the BMS group and 93.0% in the SES group (p = 0.02), mainly because of a higher target lesion revascularization rate in BMS patients (11.3% vs. 3.2%; p = 0.006). Rates of death, myocardial infarction, and stent thrombosis were not different. CONCLUSIONS Sirolimus-eluting stent implantation in STEMI patients is associated with a favorable midterm clinical and angiographic outcome compared with treatment with BMS. However, LSM raises concern about the long-term safety of SES in STEMI patients.

Automated quantification of coronary plaque with computed tomography: comparison with intravascular ultrasound using a dedicated registration algorithm for fusion-based quantification

AIMS Previous studies have used semi-automated approaches for coronary plaque quantification on multi-detector row computed tomography (CT), while an automated quantitative approach using a dedicated registration algorithm is currently lacking. Accordingly, the study aimed to demonstrate the feasibility and accuracy of automated coronary plaque quantification on cardiac CT using dedicated software with a novel 3D coregistration algorithm of CT and intravascular ultrasound (IVUS) data sets. METHODS AND RESULTS Patients who had undergone CT and IVUS were enrolled. Automated lumen and vessel wall contour detection was performed for both imaging modalities. Dedicated automated quantitative software (QCT) with a unique registration algorithm was used to fuse a complete IVUS run with a CT angiography volume using true anatomical markers. At the level of the minimal lumen area (MLA), percentage lumen area stenosis, plaque burden, and degree of remodelling were obtained on CT. Additionally, mean plaque burden was assessed for the whole coronary plaque. At the identical level within the coronary artery, the same variables were derived from IVUS. Fifty-one patients (40 men, 58 ± 11 years, 103 coronary arteries) with 146 lesions were evaluated. Quantitative computed tomography and IVUS showed good correlation for MLA (n = 146, r = 0.75, P < 0.001). At the level of the MLA, both techniques were well-correlated for lumen area stenosis (n = 146, r = 0.79, P < 0.001) and plaque burden (n = 146, r = 0.70, P < 0.001). Mean plaque burden (n = 146, r = 0.64, P < 0.001) and remodelling index (n = 146, r = 0.56, P < 0.001) showed significant correlations between QCT and IVUS. CONCLUSION Automated quantification of coronary plaque on CT is feasible using dedicated quantitative software with a novel 3D registration algorithm.

Magnetic Resonance Imaging and Spectroscopy Reveal Differential Hippocampal Changes in Anhedonic and Resilient Subtypes of the Chronic Mild Stress Rat Model

BACKGROUND Repeated exposure to mild stressors induces anhedonia-a core symptom of major depressive disorder-in up to 70% of the stress-exposed rats, whereas the remaining show resilience to stress. This chronic mild stress (CMS) model is well documented as an animal model of major depressive disorder. We examined the morphological, microstructural, and metabolic characteristics of the hippocampus in anhedonic and stress resilient rats that may mark the differential behavioral outcome. METHODS Anhedonic (n = 8), resilient (n = 8), and control (n = 8) rats were subjected to in vivo diffusion kurtosis imaging, high-resolution three-dimensional magnetic resonance imaging and proton magnetic resonance spectroscopy. RESULTS Diffusion kurtosis parameters were decreased in both CMS-exposed groups. A significant inward displacement in the ventral part of the right hippocampus was apparent in the resilient subjects and an increase of the glutamate:total creatine ratio and N-acetylaspartylglutamate:total creatine was observed in the anhedonic subjects. CONCLUSIONS Diffusion kurtosis imaging discloses subtle substructural changes in the hippocampus of CMS-exposed animals irrespective of their anhedonic or resilient nature. In contrast, proton magnetic resonance spectroscopy and magnetic resonance imaging-based shape change analysis of the hippocampus allowed discrimination of these two subtypes of stress sensitivity. Although the precise mechanism discriminating their behavior is yet to be elucidated, the present study underlines the role of the hippocampus in the etiology of depression and the induction of anhedonia. Our results reflect the potency of noninvasive magnetic resonance methods in preclinical settings with key translational benefit to and from the clinic.

Stent Malapposition After Sirolimus-Eluting and Bare-Metal Stent Implantation in Patients with ST-Segment Elevation Myocardial Infarction Acute and 9-Month Intravascular Ultrasound Results of the MISSION! Intervention Study

OBJECTIVES Acute and late stent malapposition (SM) after bare-metal stents (BMS) and sirolimus-eluting stents (SES) in ST-segment elevation myocardial infarction patients were studied. BACKGROUND Stent thrombosis may be caused by SM after primary percutaneous coronary intervention in ST-segment elevation myocardial infarction patients. METHODS Post-procedure and follow-up intravascular ultrasound data were available in 184 out of 310 patients (60%; 104 SES, 80 BMS) included in the MISSION! Intervention Study. To determine the contribution of remodeling and changes in plaque burden to the change in lumen cross-sectional area (CSA) at SM sites, the change in lumen CSA (follow-up minus post-lumen CSA) was related to the change in external elastic membrane CSA (remodeling) and change in plaque and media CSA (plaque burden). RESULTS Acute SM was found in 38.5% SES patients and 33.8% BMS patients (p = 0.51), late SM in 37.5% SES patients and 12.5% BMS patients (p < 0.001). Acquired SM was found in 25.0% SES patients and 5.0% BMS patients (p < 0.001). Predictors of acute SM were reference diameter (SES: odds ratio [OR] 3.49, 95% confidence interval [CI] 1.29 to 9.43; BMS: OR 28.8, 95% CI 4.25 to 94.5) and balloon pressure (BMS: OR 0.74, 95% CI 0.58 to 0.94). Predictors of late SM were diabetes mellitus (SES: OR 0.16, 95% CI 0.02 to 1.35), reference diameter (BMS: OR 19.2, 95% CI 2.64 to 139.7), and maximum balloon pressure (BMS: OR 0.74, 95% CI 0.55 to 1.00). Change in lumen CSA was related to change in external elastic membrane CSA (R = 0.73, 95% CI 0.62 to 0.84) after SES implantation and to change in plaque and media CSA (R = -0.62, 95% CI -0.77 to -0.46) after BMS implantation. After SES implantation, acquired SM was caused by positive remodeling in 84% and plaque reduction in 16% of patients. CONCLUSIONS Acute SM was common after SES and BMS stent implantation in ST-segment elevation myocardial infarction patients. After SES implantation, late acquired SM is common and generally caused by positive remodeling.

Multi-agent segmentation of IVUS images

Abstract A novel multi-agent image interpretation system has been developed which is markedly different from previous approaches in especially its elaborate high-level knowledge-based control over low-level image segmentation algorithms. Agents dynamically adapt segmentation algorithms based on knowledge about global constraints, contextual knowledge, local image information and personal beliefs. Generally agent control allows the underlying segmentation algorithms to be simpler and be applied to a wider range of problems with a higher reliability. The agent knowledge model is general and modular to support easy construction and addition of agents to any image processing task. Each agent in the system is further responsible for one type of high-level object and cooperates with other agents to come to a consistent overall image interpretation. Cooperation involves communicating hypotheses and resolving conflicts between the interpretations of individual agents. The system has been applied to IntraVascular UltraSound (IVUS) images which are segmented by five agents, specialized in lumen, vessel, calcified-plaque, shadow and sidebranch detection. IVUS image sequences from 7 patients were processed and vessel and lumen contours were detected fully automatically. These were compared with expert-corrected semiautomatically detected contours. Results show good correlations between agents and expert with r=0.84 for the lumen and r=0.92 for the vessel cross-sectional areas, respectively.

Atlas-based whole-body segmentation of mice from low-contrast Micro-CT data

This paper presents a fully automated method for atlas-based whole-body segmentation in non-contrast-enhanced Micro-CT data of mice. The position and posture of mice in such studies may vary to a large extent, complicating data comparison in cross-sectional and follow-up studies. Moreover, Micro-CT typically yields only poor soft-tissue contrast for abdominal organs. To overcome these challenges, we propose a method that divides the problem into an atlas constrained registration based on high-contrast organs in Micro-CT (skeleton, lungs and skin), and a soft tissue approximation step for low-contrast organs. We first present a modification of the MOBY mouse atlas (Segars et al., 2004) by partitioning the skeleton into individual bones, by adding anatomically realistic joint types and by defining a hierarchical atlas tree description. The individual bones as well as the lungs of this adapted MOBY atlas are then registered one by one traversing the model tree hierarchy. To this end, we employ the Iterative Closest Point method and constrain the Degrees of Freedom of the local registration, dependent on the joint type and motion range. This atlas-based strategy renders the method highly robust to exceptionally large postural differences among scans and to moderate pathological bone deformations. The skin of the torso is registered by employing a novel method for matching distributions of geodesic distances locally, constrained by the registered skeleton. Because of the absence of image contrast between abdominal organs, they are interpolated from the atlas to the subject domain using Thin-Plate-Spline approximation, defined by correspondences on the already established registration of high-contrast structures (bones, lungs and skin). We extensively evaluate the proposed registration method, using 26 non-contrast-enhanced Micro-CT datasets of mice, and the skin registration and organ interpolation, using contrast-enhanced Micro-CT datasets of 15 mice. The posture and shape varied significantly among the animals and the data was acquired in vivo. After registration, the mean Euclidean distance was less than two voxel dimensions for the skeleton and the lungs respectively and less than one voxel dimension for the skin. Dice coefficients of volume overlap between manually segmented and interpolated skeleton and organs vary between 0.47+/-0.08 for the kidneys and 0.73+/-0.04 for the brain. These experiments demonstrate the methods effectiveness for overcoming exceptionally large variations in posture, yielding acceptable approximation accuracy even in the absence of soft-tissue contrast in in vivo Micro-CT data without requiring user initialization.

In vivo validation of CAAS QCA-3D coronary reconstruction using fusion of angiography and intravascular ultrasound (ANGUS)†

The CAAS QCA‐3D system (Pie Medical Imaging BV, the Netherlands) was validated against 3D reconstructions based on fusion of angiography and intravascular ultrasound (ANGUS), allowing slice by slice validation of the lumen areas and 3D geometric values.

Advanced contour detection for three-dimensional intracoronary ultrasound: a validation – in vitro and in vivo

Intracoronary ultrasound (ICUS) provides high-resolution transmural images of the arterial wall. By performing a pullback of the ICUS transducer and three-dimensional reconstruction of the images, an advanced assessment of the lumen and vessel wall morphology can be obtained. To reduce the analysis time and the subjectivity of boundary tracing, automated segmentation of the image sequence must be performed. The Quantitative Coronary Ultrasound – Clinical Measurement Solutions (QCU-CMS) (semi)automated analytical software package uses a combination of transversal and longitudinal model and knowledge-guided contour detection techniques. On multiple longitudinal sections through the pullback stack, the external vessel contours are detected simultaneously, allowing mutual guidance of the detection in difficult areas. Subsequently, luminal contours are detected on these longitudinal sections. Vessel and luminal contour points are transformed to the individual cross-sections, where they guide the vessel and lumen contour detection on these transversal images. The performance of the software was validated stepwise. A set of phantoms was used to determine the systematic and random errors of the contour detection of external vessel and lumen boundaries. Subsequently, the results of the contour detection as obtained in in vivo image sets were compared with expert manual tracing, and finally the contour detection in in vivo image sequences was compared with results obtained from another previously validated ICUS quantification system. The phantom lumen diameters were underestimated by 0.1 mm, equally by the QCU-CMS software and by manual tracing. Comparison of automatically detected contours and expert manual contours, showed that lumen contours correspond very well (systematic and random radius difference: −0.025 ± 0.067 mm), while automatically detected vessel contours slightly overestimated the expert manual contours (radius difference: 0.061 ± 0.037 mm). The cross-sectional vessel and lumen areas as detected with our system and with the second computerized system showed a high correlation (r = 0.995 and 0.978, respectively). Thus, use of the new QCU-CMS analytical software is feasible and the validation data suggest its application for the analysis of clinical research.

Reproducibility of coronary Fourier domain optical coherence tomography: quantitative analysis of in vivo stented coronary arteries using three different software packages.

AIMS Fourier domain optical coherence tomography (FD OCT) enables imaging of long coronary artery segments within few seconds, employing high data acquisitions, speed and fast automated catheter pullback. However, the reproducibility of these high-speed pullbacks in the clinical situation is unknown. We tested the reproducibility of in vivo, intracoronary FD OCT and assessed the influence of different computer-assisted algorithms on quantitative analysis. METHODS AND RESULTS In patients undergoing elective coronary stenting, two repeated FD OCT pullbacks (20 mm/sec), were acquired. Lumen area (LA) and stent area (SA) were measured at 1 mm longitudinal intervals (n=18 pullbacks, n=326 frames). Inter-study variability in terms of absolute difference of mean LA, mean SA and minimum LA was very low (-0.06±0.28 mm2, -0.05±0.29 mm2 and -0.11±0.33 mm2 in software 1) Sources of variability were incomplete visualisation of the vessel circumference, ambiguous luminal borders and drift of internal catheter calibration (Z-offset). Inter-software variability for LA and SA was low (R2=0.98 ~ 1.00, p<0.01, respectively). CONCLUSIONS FD OCT shows excellent reproducibility for consecutive pullbacks and represents a reliable tool for the in vivo assessment of stented coronaries. Computer-assisted quantitative analysis of FD OCT may be a valuable tool for future studies.