R.J.M. van Geuns

Optical Coherence Tomography Assessment Of The Acute Effects Of Stent Implantation On The Vessel Wall. A Systematic Quantitative Approach

Objective: To observe and characterise vessel injury after stenting using optical coherence tomography (OCT), to propose a systematic OCT classification for periprocedural vessel trauma, to evaluate its frequency in stable versus unstable patients and to assess its clinical impact during the hospitalisation period. Setting: Stenting causes vessel injury. Design and interventions: All consecutive patients in whom OCT was performed after stent implantation were included in the study. Qualitative and quantitative assessment of tissue prolapse, intra-stent dissection and edge dissection were performed. Results: Seventy-three patients (80 vessels) were analysed. Tissue prolapse within the stented segment was visible in 78/80 vessels (97.5%). Median number of tissue prolapse sites was 8 (IQR 4–19), mean (SD) area 1.04 (0.9) mm2. Intra-stent dissection flaps were visible in 69/80 vessels (86.3%) (median number 3 (IQR 1.25–6), maximum flap length 450 (220) μm). Fifty-five out of 80 vessels (68.8%) showed dissection cavities (median number 2 (IQR 0–4.75), maximum depth 340 (170) μm). Edge dissection was visible in 20 vessels (mean (SD) length flap 744 (439) μm). The frequency of tissue prolapse or intra-stent dissection was similar in stable and unstable patients (95.6% vs 100%, p = 0.5 for tissue prolapse; 91.1% vs 82.9%, p = 0.3 for intra-stent dissection). There were no events during the hospitalisation period. Conclusions: OCT allows a detailed visualisation of vessel injury after stent implantation and enables a systematic classification and quantification in vivo. In this study, frequency of tissue prolapse or intra-stent dissections after stenting was high, irrespective of the clinical presentation of the patients, and was not associated with clinical events during hospitalisation.

Magnetic resonance imaging of the coronary arteries: clinical results from three dimensional evaluation of a respiratory gated technique

BACKGROUND Magnetic resonance coronary angiography is challenging because of the motion of the vessels during cardiac contraction and respiration. Additional challenges are the small calibre of the arteries and their complex three dimensional course. Respiratory gating, turboflash acquisition, and volume rendering techniques may meet the necessary requirements for appropriate visualisation. OBJECTIVE To determine the diagnostic accuracy of respiratory gated magnetic resonance imaging (MRI) for the detection of significant coronary artery stenoses evaluated with three dimensional postprocessing software. METHODS 32 patients referred for elective coronary angiography were studied with a retrospective respiratory gated three dimensional gradient echo MRI technique. Resolution was 1.9 × 1.25 × 2 mm. After manual segmentation three dimensional evaluation was performed with a volume rendering technique. RESULTS Overall 74% (range 50% to 90%) of the proximal and mid coronary artery segments were visualised with an image quality suitable for further analysis. Sensitivity and specificity for the detection of significant stenoses were 50% and 91%, respectively. CONCLUSIONS Volume rendering of respiratory gated MRI techniques allows adequate visualisation of the coronary arteries in patients with a regular breathing pattern. Significant lesions in the major coronary artery branches can be identified with a moderate sensitivity and a high specificity.

PCA-based groupwise image registration for quantitative MRI

Quantitative magnetic resonance imaging (qMRI) is a technique for estimating quantitative tissue properties, such as the T1 and T2 relaxation times, apparent diffusion coefficient (ADC), and various perfusion measures. This estimation is achieved by acquiring multiple images with different acquisition parameters (or at multiple time points after injection of a contrast agent) and by fitting a qMRI signal model to the image intensities. Image registration is often necessary to compensate for misalignments due to subject motion and/or geometric distortions caused by the acquisition. However, large differences in image appearance make accurate image registration challenging. In this work, we propose a groupwise image registration method for compensating misalignment in qMRI. The groupwise formulation of the method eliminates the requirement of choosing a reference image, thus avoiding a registration bias. The method minimizes a cost function that is based on principal component analysis (PCA), exploiting the fact that intensity changes in qMRI can be described by a low-dimensional signal model, but not requiring knowledge on the specific acquisition model. The method was evaluated on 4D CT data of the lungs, and both real and synthetic images of five different qMRI applications: T1 mapping in a porcine heart, combined T1 and T2 mapping in carotid arteries, ADC mapping in the abdomen, diffusion tensor mapping in the brain, and dynamic contrast-enhanced mapping in the abdomen. Each application is based on a different acquisition model. The method is compared to a mutual information-based pairwise registration method and four other state-of-the-art groupwise registration methods. Registration accuracy is evaluated in terms of the precision of the estimated qMRI parameters, overlap of segmented structures, distance between corresponding landmarks, and smoothness of the deformation. In all qMRI applications the proposed method performed better than or equally well as competing methods, while avoiding the need to choose a reference image. It is also shown that the results of the conventional pairwise approach do depend on the choice of this reference image. We therefore conclude that our groupwise registration method with a similarity measure based on PCA is the preferred technique for compensating misalignments in qMRI.

Long-term outcome of the unrestricted use of everolimus-eluting stents compared to sirolimus-eluting stents and paclitaxel-eluting stents in diabetic patients: The Bern–Rotterdam diabetes cohort study

BACKGROUND Newer generation everolimus-eluting stents (EES) improve clinical outcome compared to early generation sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES). We investigated whether the advantage in safety and efficacy also holds among the high-risk population of diabetic patients during long-term follow-up. METHODS Between 2002 and 2009, a total of 1963 consecutive diabetic patients treated with the unrestricted use of EES (n=804), SES (n=612) and PES (n=547) were followed throughout three years for the occurrence of cardiac events at two academic institutions. The primary end point was the occurrence of definite stent thrombosis. RESULTS The primary outcome occurred in 1.0% of EES, 3.7% of SES and 3.8% of PES treated patients ([EES vs. SES] adjusted HR=0.58, 95% CI 0.39-0.88; [EES vs. PES] adjusted HR=0.29, 95% CI 0.13-0.67). Similarly, patients treated with EES had a lower risk of target-lesion revascularization (TLR) compared to patients treated with SES and PES ([EES vs. SES], 5.6% vs. 11.5%, adjusted HR=0.68, 95% CI: 0.55-0.83; [EES vs. PES], 5.6% vs. 11.3%, adjusted HR=0.51, 95% CI: 0.33-0.77). There were no differences in other safety end points, such as all-cause mortality, cardiac mortality, myocardial infarction (MI) and MACE. CONCLUSION In diabetic patients, the unrestricted use of EES appears to be associated with improved outcomes, specifically a significant decrease in the need for TLR and ST compared to early generation SES and PES throughout 3-year follow-up.

Heart disease in the Netherlands: a quantitative update

In this review we discuss cardiovascular mortality, incidence and prevalence of heart disease, and cardiac interventions and surgery in the Netherlands. We combined most recently available data from various Dutch cardiovascular registries, Dutch Hospital Data (LMR), Statistics Netherlands (CBS), and population-based cohort studies, to provide a broad quantitative update. The absolute number of people dying from cardiovascular diseases is declining and cardiovascular conditions are no longer the leading cause of death in the Netherlands. However, a substantial burden of morbidity persists with 400,000 hospitalisations for cardiovascular disease involving over 80,000 cardiac interventions annually. In the Netherlands alone, an estimated 730,000 persons are currently diagnosed with coronary heart disease, 120,000 with heart failure, and 260,000 with atrial fibrillation. These numbers emphasise the continuous need for dedicated research on prevention, diagnosis, and treatment of heart disease in our country.

Statistical coronary motion models for 2D + t/3D registration of X-ray coronary angiography and CTA

Accurate alignment of intra-operative X-ray coronary angiography (XA) and pre-operative cardiac CT angiography (CTA) may improve procedural success rates of minimally invasive coronary interventions for patients with chronic total occlusions. It was previously shown that incorporating patient specific coronary motion extracted from 4D CTA increases the robustness of the alignment. However, pre-operative CTA is often acquired with gating at end-diastole, in which case patient specific motion is not available. For such cases, we investigate the possibility of using population based coronary motion models to provide constraints for the 2D+t/3D registration. We propose a methodology for building statistical motion models of the coronary arteries from a training population of 4D CTA datasets. We compare the 2D+t/3D registration performance of the proposed statistical models with other motion estimates, including the patient specific motion extracted from 4D CTA, the mean motion of a population, the predicted motion based on the cardiac shape. The coronary motion models, constructed on a training set of 150 patients, had a generalization accuracy of 1mm root mean square point-to-point distance. Their 2D+t/3D registration accuracy on one cardiac cycle of 12 monoplane XA sequences was similar to, if not better than, the 4D CTA based motion, irrespective of which respiratory model and which feature based 2D/3D distance metric was used. The resulting model based coronary motion estimate showed good applicability for registration of a subsequent cardiac cycle.

Oriented Gaussian Mixture Models for Nonrigid 2D/3D Coronary Artery Registration

2D/3D registration of patient vasculature from preinterventional computed tomography angiography (CTA) to interventional X-ray angiography is of interest to improve guidance in percutaneous coronary interventions. In this paper we present a novel feature based 2D/3D registration framework, that is based on probabilistic point correspondences, and show its usefulness on aligning 3D coronary artery centerlines derived from CTA images with their 2D projection derived from interventional X-ray angiography. The registration framework is an extension of the Gaussian mixture model (GMM) based point-set registration to the 2D/3D setting, with a modified distance metric. We also propose a way to incorporate orientation in the registration, and show its added value for artery registration on patient datasets as well as in simulation experiments. The oriented GMM registration achieved a median accuracy of 1.06 mm, with a convergence rate of 81% for nonrigid vessel centerline registration on 12 patient datasets, using a statistical shape model. The method thereby outperformed the iterative closest point algorithm, the GMM registration without orientation, and two recently published methods on 2D/3D coronary artery registration.

GPU accelerated alignment of 3-D CTA with 2-D X-ray data for improved guidance in coronary interventions

This paper presents a 2-D/3-D registration method for the alignment of cardiac X-ray images to ECG gated CTA data of the coronary arteries. The purpose of our work is to provide visualization of instruments in relation to pre-operative CTA data during interventional cardiology for improved image guidance, especially in complex procedures. The method utilizes the graphical processing unit (GPU) for rendering of digitally reconstructed radiographs (DRRs) from a 3-D CTA-derived coronary model. Using a multi-scale gradient ascent framework, the normalized cross correlation between the simulated and real X-ray image is optimized. Quantitative evaluation is performed by computing the projection error of the vessel centerlines, which was on average 1.34 mm.

Comprehensive visualization of multimodal cardiac imaging data for assessment of coronary artery disease: first clinical results of the SMARTVis tool.

PurposeIn clinical practice, both coronary anatomy and myocardial perfusion information are needed to assess coronary artery disease (CAD). The extent and severity of coronary stenoses can be determined using computed tomography coronary angiography (CTCA); the presence and amount of ischemia can be identified using myocardial perfusion imaging, such as perfusion magnetic resonance imaging (PMR). To determine which specific stenosis is associated with which ischemic region, experts use assumptions on coronary perfusion territories. Due to the high variability between patient’s coronary artery anatomies, as well as the uncertain relation between perfusion territories and supplying coronary arteries, patient-specific systems are needed.Material and methodsWe present a patient-specific visualization system, called Synchronized Multimodal heART Visualization (SMARTVis), for relating coronary stenoses and perfusion deficits derived from CTCA and PMR, respectively. The system consists of the following comprehensive components: (1) two or three-dimensional fusion of anatomical and functional information, (2) automatic detection and ranking of coronary stenoses, (3) estimation of patient-specific coronary perfusion territories.ResultsThe potential benefits of the SMARTVis tool in assessing CAD were investigated through a case-study evaluation (conventional vs. SMARTVis tool): two experts analyzed four cases of patients with suspected multivessel coronary artery disease. When using the SMARTVis tool, a more reliable estimation of the relation between perfusion deficits and stenoses led to a more accurate diagnosis, as well as a better interobserver diagnosis agreement.ConclusionThe SMARTVis comprehensive visualization system can be effectively used to assess disease status in multivessel CAD patients, offering valuable new options for the diagnosis and management of these patients.

Volume coronary angiography using targeted scans (VCATS): a new strategy in MR coronary angiography.

The aim of this study was to explore the clinical possibilities of a new strategy for magnetic resonance imaging of the coronary arteries. Thirteen patients were studied by volume coronary angiography using targeted scans (VCATS) to visualize the major coronary arteries in a series of breath-holds. The proximal coronary arteries were clearly seen in 92% and the mid segments in 50–70% of the patients. VCATS was able to visualize a total vessel length of the left main (LM) (mean: 9.4 ± 3.4 mm), of the left anterior descending (LAD) 69 ± 20 mm, of the right coronary artery (RCA) 90 ± 33 mm and of the left circumflex (LCX) 41 ± 18 mm. There was a reasonable correlation between the VCATS and conventional coronary angiography (CAG) for vessel diameter (r = 0.71), with a slight overestimation of 0.7 mm by VCATS. There were nine significant stenoses present of which six were correctly detected, three were missed and one false positive was present. VCATS is fast strategy for visualizing the major coronary artery branches and has the potential to detect significant stenoses in these branches.