Validation of cadmium-zinc-telluride camera for measurement of left ventricular systolic performance.

BACKGROUND: There are paucity of data comparing measurements of left ventricular systolic performance using cadmium-zinc-telluride (CZT) semiconductor cameras with other imaging modalities. This study compared the new system with echocardiography (echo) and cardiac magnetic resonance (CMR) imaging. METHODS: 60 Patients presenting with ST-elevated myocardial infarction (MI) were included. Each patient underwent echo, myocardial perfusion imaging using Spectrum Dynamics D-SPECT(r) (CZT-SPECT), and CMR 6 weeks after MI. The primary endpoint was the agreement between CZT-SPECT and CMR for left ventricular ejection fraction (LVEF) measurement. RESULTS: 48 of the 60 patients underwent all 3 studies (echo, CMR, and CZT-SPECT) 40 days after admission. CZT-SPECT and CMR LVEF were well correlated (r = .79, P < .0001), as well as CZT-SPECT vs echo and CMR vs echo (r = .79 and .84, respectively, P < .0001). The segmental LV wall thickening and wall motion also showed good concordance between three techniques. CONCLUSIONS: CZT-SPECT is reliable for LVEF measurement.

Contact position analysis of deep brain stimulation electrodes on post-operative CT images.

PURPOSE: Groups performing deep brain stimulation advocate post-operative imaging [magnetic resonance imaging (MRI) or computer tomography (CT)] to analyse the position of each electrode contact. The artefact of the Activa 3389 electrode had been described for MRI but not for CT. We undertook an electrode artefact analysis for CT imaging to obtain information on the artefact dimensions and related electrode contact positions. METHODS: The electrode was fixed on a phantom in a set position and six acquisitions were run (in-vitro study). The artefacts were compared with the real electrode position. Ten post-operative acquisitions were analysed (in-vivo analysis). We measured: H (height of the lateral black artefact), D (distance between the beginning of the white and the lateral black artefacts) and W (maximal artefact width), representing respectively the lengths of the four contacts and the electrode tip and width of the contact zone. A Student t-test compared the results: in vivo vs in vitro and coronal vs sagittal reconstructions along the electrode. RESULTS: The limits of the lateral black artefact around the electrode contacts corresponded to the final electrode position. There was no significant difference for D (in vivo, 1.1 +/- 0.1 mm; in vitro, 1.2 +/- 0.2 mm; p = 0.213), while W and H differed slightly (in vivo, W = 3.3 +/- 0.2 mm, H = 7.7 +/- 0.2 mm; in vitro, W = 3.1 +/- 0.1 mm, H = 7.5 +/- 0.2 mm). Results obtained with sagittal and coronal reconstructions were similar (p > 0.6). CONCLUSIONS: Precise three-dimensional (3D) localisation of the four-contact zone of the electrode can be obtained by CT identification of the limits of the lateral black artefact. The relative position of the four contacts is deduced from the size of the contacts and the inter-contact distance. Sagittal and coronal reconstructions along the electrode direction should be considered for the identification of the four electrode contacts. CT offers a useful alternative to post-operative MRI.

Fast simulation of stent deployment with plastic beam elements.

Coronary stent deployment is a reference cardiology intervention, used to treat atherosclerosis and prevent heart attacks. The outcomes of the intervention highly depend on the accuracy of the stent apposition, which could benefit from per-operative prediction tools. In this paper, we propose a fast and mechanically realistic 3D simulation of a coronary stent expansion. Our simulation relies on the finite element method and involves serially linked beam elements to model the slender geometry of a stent. The elements are implemented with a non-linear elasto-plastic behavior, describing realistically the complex deformation of a balloon-expandable stent. As a proof of concept, we simulated the free expansion of a coronary stent. The simulation output was compared with micro-CT data, acquired experimentally during the device expansion. Results show that the plastic beam model is able to reproduce successfully the final geometry of the stent. In addition, the use of 1D elements allows to achieve a significantly lower computational time than for equivalent literature simulations, based on 3D elements. This preliminary work highlights the compatibility of our method with clinical routine in terms of execution time. Further developments include the application of the method to more advanced simulation scenarios, with the addition of a personalized artery model.

Computed and Subjective Blue Scleral Color Analysis as a Diagnostic Tool for Iron Deficiency: A Pilot Study.

Iron deficiency (ID) is the most common nutritional deficiency. ID diagnosis requires ferritin measurement because clinical findings are poor and nonspecific. We studied the diagnostic value of blue sclera, which was scarcely reported as a specific and sensitive sign of ID. We enrolled 74 patients suspected of having ID. Pictures of their eyes were taken using a smartphone under similar daylight conditions. Three independent physicians graded the scleral color, and a computer analysis yielded the blue percentile of the sclera image. Final analysis included 67 patients (mean age 59.9 ± 20.1 years). Fifty-one had ID. Subjective blue scleral color was associated with ID for physician 1 (64.5% vs. 86.1%, p = 0.03). Sensitivity was 60.8% (CI95: 46.1%; 74.2%), specificity 68.8% (CI95: 41.3%; 89%), and positive predictive value 86.1% (CI95: 70.5%; 95.3%). A marginal difference was observed for other physicians (p = 0.05). Computer analysis showed higher blue in the ID group (p = 0.04). The area under the receiver operating characteristic (ROC) curve was 0.7 (0.54; 0.85). Sensitivity was 78.4% (CI95: 63.7%; 88.7%), specificity was 50% (CI95: 24.7%; 75.3%). Assessment of blue sclera was not influenced by iris color, sex, or anemia. We showed that blue sclera has good positive predictive value for ID diagnosis, and computer analysis was correlated to clinical assessment. Improvement of this innovative, non-invasive method could provide an easy handling and inexpensive diagnosis tool for ID.

Contour segmentation of the intima, media, and adventitia layers in intracoronary OCT images: application to fully automatic detection of healthy wall regions.

PURPOSE: Quantitative and automatic analysis of intracoronary optical coherence tomography images is useful and time-saving to assess cardiovascular risk in the clinical arena. METHODS: First, the interfaces of the intima, media, and adventitia layers are segmented, by means of an original front propagation scheme, running in a 4D multi-parametric space, to simultaneously extract three non-crossing contours in the initial cross-sectional image. Second, information resulting from the tentative contours is exploited by a machine learning approach to identify healthy and diseased regions of the arterial wall. The framework is fully automatic. RESULTS: The method was applied to 40 patients from two different medical centers. The framework was trained on 140 images and validated on 260 other images. For the contour segmentation method, the average segmentation errors were [Formula: see text] for the intima-media interface, [Formula: see text] for the media-adventitia interface, and [Formula: see text] for the adventitia-periadventitia interface. The classification method demonstrated a good accuracy, with a median Dice coefficient equal to 0.93 and an interquartile range of (0.78-0.98). CONCLUSION: The proposed framework demonstrated promising offline performances and could potentially be translated into a reliable tool for various clinical applications, such as quantification of tissue layer thickness and global summarization of healthy regions in entire pullbacks.

Estimation of Myocardial Strain and Contraction Phase From Cine MRI Using Variational Data Assimilation.

This paper presents a new method to estimate left ventricle deformations using variational data assimilation that combines image observations from cine MRI and a dynamic evolution model of the heart. The main contribution of the model is that it embeds parameters modeling the contraction / relaxation process. It estimates myocardial motion and contraction parameters simultaneously, providing accurate complementary information for diagnosis. The method was applied to synthetic datasets with known ground truth motion and to 47 patients MRI datasets acquired at three slice locations (base, mid-ventricle and apex). Radial and circumferential strain components were compared to those obtained with a reference tag tracking software, exhibiting good agreement with intraclass correlation coefficients (ICC) above 0.8. Results were also evaluated against wall motion score indices used to assess cardiac kinetics in clinical practice. The assimilation process overcame issues caused by temporal artifacts as a result of the dynamic model, compared to using the observation term alone. Moreover we found that the new dynamic model, consisting of a piecewise transport model acting independently on systole and diastole performed better than the standard continuous transport model, which oversmooths temporal variations. Estimated strain and contraction parameters significantly correlated to clinical scores, making them promising features for diagnosing not only hypokinesia but also dyskinesia.

Radiographic stereometry for non-metal-backed acetubular cups: 3D wear estimation and related uncertainty.

The aim of this work was to assess the 3D wear of non-metal-backed acetubular cups from two conventional digitized radiographs. The centers of the femoral head and the metal ring in the equatorial plane of the cup are located using 3D pose techniques for spheres and circles from sampled points in the images. The method used to locate these points of interest and also estimate their covariance is fully described in previous work. The covariance is used to decrease the bias of the pose estimation, while bootstrapping decreases its variance and gives access to the directions of minimal variability between the two centers for each image. These directions are used to produce the final distance after reconstruction. Results are compared with the 2D technique working on a single anteroposterior (AP) radiograph and assuming null lateral wear. Validation is performed on acetubular cups: (a) simulated by Monte-Carlo, (b) implanted on a pelvic model, and (c) acquired on patients just after arthroplasty. The accuracy in wear for simulation increases from about one to four hundredths of a millimeter as caudal and cranial absolute angulations decreases from 45 degrees to 30 degrees . It is more difficult to assess for real prostheses, but results are shown to lie within the manufacturer's dimensional tolerances. Globally, the access to the lateral wear is obtained at the expense of confidence in the global linear wear (0.06 mm), which is doubled with regard to 2D technique but still satisfying for clinical use, whereas the bias of the measurement is decreased.

Automated peroperative assessment of stents apposition from OCT pullbacks.

This study's aim was to control the stents apposition by automatically analyzing endovascular optical coherence tomography (OCT) sequences. Lumen is detected using threshold, morphological and gradient operators to run a Dijkstra algorithm. Wrong detection tagged by the user and caused by bifurcation, struts'presence, thrombotic lesions or dissections can be corrected using a morphing algorithm. Struts are also segmented by computing symmetrical and morphological operators. Euclidian distance between detected struts and wall artery initializes a stent's complete distance map and missing data are interpolated with thin-plate spline functions. Rejection of detected outliers, regularization of parameters by generalized cross-validation and using the one-side cyclic property of the map also optimize accuracy. Several indices computed from the map provide quantitative values of malapposition. Algorithm was run on four in-vivo OCT sequences including different incomplete stent apposition's cases. Comparison with manual expert measurements validates the segmentation׳s accuracy and shows an almost perfect concordance of automated results.

Improved Estimation of Cardiac Function Parameters Using a Combination of Independent Automated Segmentation Results in Cardiovascular Magnetic Resonance Imaging.

This work aimed at combining different segmentation approaches to produce a robust and accurate segmentation result. Three to five segmentation results of the left ventricle were combined using the STAPLE algorithm and the reliability of the resulting segmentation was evaluated in comparison with the result of each individual segmentation method. This comparison was performed using a supervised approach based on a reference method. Then, we used an unsupervised statistical evaluation, the extended Regression Without Truth (eRWT) that ranks different methods according to their accuracy in estimating a specific biomarker in a population. The segmentation accuracy was evaluated by estimating six cardiac function parameters resulting from the left ventricle contour delineation using a public cardiac cine MRI database. Eight different segmentation methods, including three expert delineations and five automated methods, were considered, and sixteen combinations of the automated methods using STAPLE were investigated. The supervised and unsupervised evaluations demonstrated that in most cases, STAPLE results provided better estimates than individual automated segmentation methods. Overall, combining different automated segmentation methods improved the reliability of the segmentation result compared to that obtained using an individual method and could achieve the accuracy of an expert.

Nonsupervised ranking of different segmentation approaches: application to the estimation of the left ventricular ejection fraction from cardiac cine MRI sequences.

A statistical methodology is proposed to rank several estimation methods of a relevant clinical parameter when no gold standard is available. Based on a regression without truth method, the proposed approach was applied to rank eight methods without using any a priori information regarding the reliability of each method and its degree of automation. It was only based on a prior concerning the statistical distribution of the parameter of interest in the database. The ranking of the methods relies on figures of merit derived from the regression and computed using a bootstrap process. The methodology was applied to the estimation of the left ventricular ejection fraction derived from cardiac magnetic resonance images segmented using eight approaches with different degrees of automation: three segmentations were entirely manually performed and the others were variously automated. The ranking of methods was consistent with the expected performance of the estimation methods: the most accurate estimates of the ejection fraction were obtained using manual segmentations. The robustness of the ranking was demonstrated when at least three methods were compared. These results suggest that the proposed statistical approach might be helpful to assess the performance of estimation methods on clinical data for which no gold standard is available.

Spatial distribution of neo-intimal hyperplasia 6 months after zotarolimus-eluting stent implantation, analysed by optical coherence tomography.

BACKGROUND: Optical coherence tomography is a high-resolution imaging technology that allows in vivo assessment of neointimal hyperplasia and strut coverage after coronary stenting. AIM: Assessment of spatial distribution of healing, 6 months after zotarolimus-eluting stent implantation. METHODS: Forty-two zotarolimus-eluting stents were monitored by optical coherence tomography 6 months after implantation. Mean neointimal strut coverage thickness and percentage of neointimal hyperplasia were measured every millimetre. Non-covered strut ratios were assessed on each slice. In addition, the spatial distribution of neointimal hyperplasia and strut coverage were analysed longitudinally on five stent segments and axially on each slice. RESULTS: There were no clinical events at 6 months under dual antiplatelet therapy. The optical coherence tomography analysis showed a mean neointimal hyperplasia thickness of 333±147µm and neointimal hyperplasia obstruction of 36.1±12.3%. The percentage of covered struts at 6 months was very high (98.9%). Only 6/745 slices analysed (0.8%) had non-covered strut ratios exceeding 30%. There was no significant heterogeneity in either longitudinal or axial neointimal hyperplasia distribution. No thrombi were observed. CONCLUSION: This optical coherence tomography study found relatively constant neointimal hyperplasia thickness, regardless of the zotarolimus-eluting stent length or diameter. This spatially homogeneous neointimal hyperplasia was associated with near-total coverage of all struts, 6 months after implantation.

Comparison of different segmentation approaches without using gold standard. Application to the estimation of the left ventricle ejection fraction from cardiac cine MRI sequences.

A statistical method is proposed to compare several estimates of a relevant clinical parameter when no gold standard is available. The method is illustrated by considering the left ventricle ejection fraction derived from cardiac magnetic resonance images and computed using seven approaches with different degrees of automation. The proposed method did not use any a priori regarding with the reliability of each method and its degree of automation. The results showed that the most accurate estimates of the ejection fraction were obtained using manual segmentations, followed by the semiautomatic methods, while the methods with the least user input yielded the least accurate ejection fraction estimates. These results were consistent with the expected performance of the estimation methods, suggesting that the proposed statistical approach might be helpful to assess the performance of estimation methods on clinical data for which no gold standard is available.

In vivo supervised analysis of stent reendothelialization from optical coherence tomography.

The aim of this study is to interactively assess reendothelialization of stents at an accuracy of down to a few micrometer by analyzing endovascular optical coherence tomography (OCT) sequences. Vessel wall and stent struts are automatically detected by using morphological, gradient, and symmetry operators coupled with active contour models; alerts are issued to ask for user supervision over some extreme irregular geometries caused by thrombotic lesions or dissections. A complete distance map is then computed from sparse distances measured between wall and struts. Missing values are interpolated by thin-plate spline (TPS) functions. Accuracy and robustness are increased by taking into account the inhomogeneity of data points and integrating in the same framework orthogonalized forward selection of support points, optimal selection of regularization parameters by generalized cross-validation, and rejection of detection outliers. Validation is performed on simulated data, phantom acquisitions and 11 typical in vivo OCT sequences. The comparison against manual expert measurements demonstrates a bias of the order of OCT resolution (less than 10 microm) and a standard deviation of the order of the strut width (less than 150 microm).

High-resolution coronary imaging by optical coherence tomography: Feasibility, pitfalls and artefact analysis.

BACKGROUND: Optical coherence tomography is an imaging method that enables cardiologists to study atheromatous plaques, and to check the implantation and evolution of coronary stents. It is an invasive technique, providing high-resolution (10 microm) in vivo images, but with limitations and artefacts that need to be understood before the field of application can be extended. AIM: To determine the feasibility and limitations of optical coherence tomography coronary imaging from a single-centre experience. METHODS: We analysed the first 301 optical coherence tomography (version M2, LightLab Imaging) sequences obtained in our department from examination of 73 patients. RESULTS: Results showed that 92% of sequences for selected lesions were usable, with a mean examination time of 17 min. Only one complication occurred (ventricular fibrillation, reduced by external electroshock). In our registry, sequence quality depended on operator experience (improving after 20 examinations), and was impaired by artefacts, especially in right coronary analysis and in arteries of greater than 3.5 mm calibre. CONCLUSIONS: Proximal coronary occlusion and the distal flush quality currently required for quality imaging should no longer be indispensable with the new generation of optical coherence tomography systems.

In vivo OCT coronary imaging augmented with stent reendothelialization score.

The aim of this study is to automatically assess reendothelialization of stents at an accuracy of down to a few microns by analyzing endovascular optical coherence tomography (OCT) sequences. Vessel wall and struts are automatically detected and complete distance map is then computed from sparse distances measured between wall and struts by thin-plate spline (TPS) interpolation. A reendothelialization score is mapped onto the geometry of the coronary artery segment. Accuracy and robustness are increased by taking into account the inhomogeneity of datapoints and integrating in the same framework orthogonalized forward selection of support points, optimal selection of regularization parameters by generalized cross-validation (GCV) and rejection of detection outliers. The comparison against manual expert measurements for a phantom study and 12 in vivo stents demonstrates no significant discordance with variability of the order of the strut thickness.

Comparative analysis of neointimal coverage with paclitaxel and zotarolimus drug-eluting stents, using optical coherence tomography 6 months after implantation.

BACKGROUND: Intrastent thrombosis, while rare, has a poor prognosis. Strut non-coverage is one causal factor, especially in cases of resistance to or premature discontinuation of dual antiplatelet therapy. AIM: To compare neointimal coverage with paclitaxel and zotarolimus drug-eluting stents, using optical coherence tomography (OCT). METHODS: Twenty-two drug-eluting stents (11 paclitaxel-eluting stents and 11 zotarolimus-eluting stents) were examined by OCT, 6 months after implantation. Mean neointimal strut-coverage thickness and percentage neointimal hyperplasia were measured every millimetre. On each OCT image, struts were classified into one of four categories: well-apposed to vessel wall with apparent neointimal coverage; well-apposed to vessel wall without neointimal coverage; malapposed to the vessel wall; or located on a major side branch. RESULTS: OCT analysis showed a lower percentage of neointimal hyperplasia with paclitaxel-eluting stents than with zotarolimus-eluting stents (17% vs 38% and mean thickness 154 microm vs 333 microm, respectively; p<0.0001). The rate of strut-coverage was greater with zotarolimus-eluting stents than with paclitaxel-eluting stents (99.1% vs 87.1%, respectively; p<0.0001). A non-covered/covered strut ratio greater than 0.3 was observed in 0.5% of zotarolimus-eluting stent OCT images compared with 18% of paclitaxel-eluting stent OCT images (p<0.0001). CONCLUSION: Six months after implantation, neointimal hyperplasia was greater with zotarolimus-eluting stents compared with paclitaxel-eluting stents. Conversely, neointimal strut-coverage was better with zotarolimus-eluting stents.

Early detection and monitoring of cartilage alteration in the experimental meniscectomised guinea pig model of osteoarthritis by 99mTc-NTP 15-5 scintigraphy.

PURPOSE: This study in the meniscectomised guinea pig aimed to demonstrate that the radiotracer (99m)Tc-NTP 15-5 would have pathophysiological validity for in vivo osteoarthritis imaging. METHODS: The specificity of (99m)Tc-NTP 15-5 for cartilage was determined in healthy animals (n = 13), by tissue radioactivity counting, joint autoradiography and scintigraphy. (99m)Tc-NTP 15-5 scintigraphy was performed at 20, 50, 80, 115, 130, 150 and 180 days after medial meniscectomy (n = 10 MNX) or sham operation (n = 5), and scintigraphic ratios (operated/contralateral) were calculated for femoral (F) and tibial (T) areas. F and T ratios were compared with those of (99m)Tc-MDP bone scintigraphy. At the study end-point, autoradiographic analysis of joint (99m)Tc-NTP 15-5 distribution and macroscopic scoring of cartilage integrity were performed. RESULTS: The high and specific accumulation of (99m)Tc-NTP 15-5 in normal cartilage (about 5.5 +/- 1.7 % of injected dose/g of tissue), which permitted joint imaging with high contrast, was affected by osteoarthritis. In the MNX group, (99m)Tc-NTP 15-5 accumulation in cartilage within the operated joint, relative to the contralateral joint, was observed to change in the same animals as pathology progressed. Although F and T ratios were significantly higher in MNX (F = 1.7 +/- 0.2; T = 1.6 +/- 0.1) than in shams (F = 1.0 +/- 0.1; T = 1.0 +/- 0.1) at day 50, they were significantly lower in MNX (F = 0.6 +/- 0.1; T = 0.7 +/- 0.1) than in shams (F = 1.0 +/- 0.1; T = 0.9 +/- 0.1) at day 180. No change in (99m)Tc-MDP uptake was observed over 6 months. Macroscopic analysis confirmed features of osteoarthritis only in MNX knees. CONCLUSION: These results in MNX guinea pigs provide additional support for the use of (99m)Tc-NTP 15-5 for in vivo imaging of osteoarthritis.